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We use very long baseline interferometry (VLBI) at 8.4 and 22 GHz - higher frequencies than those of previous surveys - in conjunction with nearly simultaneous radio to submillimeter-wave observations to determine the parameters of the synchrotron spectrum and to examine the compact angular structure of a subset of sources from our sample. These parameters are used to predict the SSC X-ray flux densities. Seven of 30 sources have predicted self-Compton X-ray flux densities well above the observed flux densities obtained with the ROSAT satellite unless one assumes that the radiating plasma experiences bulk relativistic motion directed toward the observer's line of sight. Three of these seven sources are detected at gamma-ray frequencies. Model spectra show that the X-rays are consistent with the first-order SSC process, with the simultaneous multiwaveband spectrum of the quasar 0836+710 obtained in 1992 March being very well fitted by SSC emission from a uniform, relativistically moving source. The gamma-rays are not produced via second-order self-Compton scattering but rather by either first-order self-Compton scattering or some other process.

A comparison of the ROSAT X-ray flux densities and those obtained earlier with the Einsteim Observatory show that several FSRQs are X-ray variables on timescales of about a decade. Several sources that were observed more than once with ROSAT also show variability on timescales of 1-2 yr, with the X-ray variability in these cases often associated with millimeter-wave variability and lower VLBI core-to-jet flux ratios. Detections at gamma-ray energies also appear to be related to increases in the radio to millimeter-wave flux densities.

Statistical analysis shows that the millimeter-wave and x-ray luminosities for the sample are strongly correlated, with a linear regression slope ~ 0.65. The peak in the distribution of X-ray to millimeter spectral indices also indicates a strong connection between millilmeter-wave and X-ray emission. Particularly interesting is a correlation between X-ray to millimeter spectral index and fraction of flux density contained in the VLBI core. This tendency toward high X-rays fluxes from sources with stronger jet emission implies that the knots in the jet are prominent sources of X-rays.

Metsähovi Radio Observatory /
Abstracts

Savolainen, T., Wiik, K., Valtaoja, E., Tornikoski, M.:
Multifrequency VLBA Monitoring of 3C273 during INTEGRAL Campaing in 2003. I. Kinematics of the Prasec Scale Jet.
Astronomy and Astrophysics, Vol. 446 pp. 71-85, 2006.
Abstracts In this first of a series of papers describing polarimetric multifrequency Very Long Baseline Array (VLBA) monitoring of 3C 273 during a simultaneous campaign with the INTEGRAL &gamma -ray satellite in 2003, we present 5 Stokes I images and source models at 7 mm. We show that a part of the inner jet (1-2 milliarcsec from the core) is resolved in a direction transverse to the flow, and we analyse the kinematics of the jet within the first 10 mas. Based on the VLBA data and simultaneous single-dish flux density monitoring, we determine an accurate value for the Doppler factor of the parsec scale jet, and using this value with observed proper motions, we calculate the Lorentz factors and the viewing angles for the emission components in the jet. Our data indicates a significant velocity gradient across the jet with the components travelling near the southern edge being faster than the components with more northern path. We discuss our observations in the light of jet precession model and growing plasma instabilities.

Nieppola, E., Tornikoski, M., Valtaoja, E.
Spectral energy distributions of a complete sample of BL Lacertae objects.
Astronomy and Astrophysics, Vol. 445, pp. 441-450, 2006.
Abstracts We have collected a large amount of multifrequency data for objects in the Metsähovi Radio Observatory BL Lacertae sample and computed their spectral energy distributions (SED) in the log ν - log νF - representation. This is the first time the SEDs of BL Lacs have been studied with a sample of over 300 objects. The synchrotron components of the SEDs were fitted with a parabolic function to determine the synchrotron peak frequency, &nu_peak. We checked the dependence between luminosities at several frequency bands and synchrotron peak frequency to test the blazar sequence scenario, which states that the source luminosity depends on the location of the synchrotron peak. We also calculated broad band spectral indices and plotted them against each other and &nu_peak.

The range of &nu_peak in our study was considerably extended compared to previous studies. There were 22 objects for which log &nu_peak > 19. The data shows that at 5 GHz, 37 GHz, and 5500 Å, there is negative correlation between luminosity and &nu_peak, whereas in X-rays the correlation turns slightly positive. There is no significant correlation between source luminosity at synchrotron peak and &nu_peak. Several low radio luminosity-low energy peaked BL Lacs were found. The negative correlation between broad band spectral indices and &nu_peak is also significant, although there is substantial scatter. Therefore we find that neither &alpha_rx nor &alpha_ro can be used to determine the synchrotron peak of BL Lacs. On the grounds of our results, we conclude that the blazar sequence scenario is not valid. In all our results, the BL Lac population is continuous with no hint of the bimodality of the first BL Lac samples.

Lindfors, E.J., Türler, M., Valtaoja, E., Aller, H., Aller, M., Mazin, D., Raiteri, C.M., Stevens, J.A., Tornikoski, M., Tosti, G., Villata, M.:
Synchrotron flaring in the jet of 3C 279.
Astronomy and Astrophysics, Vol. 440, pp. 845-853, 2005.
Abstracts

Raiteri, C.M., Villata, M., Ibrahimov, M.A., Larionov, V.M., Kadler, M., Aller, H.D., Aller, M.F., Kovalev, Y.Y., Lanteri, L., Nilsson, K., Papadakis, I.E., Pursimo, T., Romero, G.E., Teräsranta, H., Tornikoski, M., Arkharov, A.A., Barnaby, D., Berdyugin, A., Böttcher, M., Byckling, K., Carini, M.T., Carosati, D., Cellone, S.A., Ciprini, S., Combi, J.A., Crapanzano, S., Crowe, R., Di Paola, A., Dolci, M., Fuhrmann, L., Gu, M., Hagen-Thorn, V.A., Hakala, P., Impellizzeri, V., Jorstad, S., Kerp, J., Kimeridze, G.N., Kovalev, Yu. A., Kraus, A., Krichbaum, T.P., Kurtanidze, O.M., Lähteenmäki, A., Lindfors, E., Mingaliev, M.G., Nesci, R., Nikolashvili, M.G., Ohlert, J., Orio, M., Ostorero, L., Pasanen, M., Pati, A., Poteet, C., Ros, E., Ros, J.A., Shastri, P., Sigua, L.A., Sillanpää, A., Smith, N., Takalo, L.O., Tosti, G., Vasileva, A., Wagner, S.J., Walters, R., Webb, J.R., Wills, W., Witzel, A., Xilouris, E.:
The WEBT campaign to observe AO 0235+16 in the 2003-2004 observing season. Results from radio-to-optical monitoring and XMM-Newton observations.
Astronomy and Astrophysics, Vol. 438, pp. 39-53, 2005.
Abstract A multiwavelength campaign to observe the BL Lac object AO 0235+16 (z=0.94) was set up by the Whole Earth Blazar Telescope (WEBT) collaboration during the observing seasons 2003-2004 and 2004-2005, involving radio, near-IR and optical photometric monitoring, VLBA monitoring, optical spectral monitoring, and three pointings by the XMM-Newton satellite. Here we report on the results of the first season, which involved the participation of 24 optical and near-IR telescopes and 4 radio telescopes, as well as the first XMM-Newton pointing, which occurred on January 18-19, 2004. Unpublished data from previous epochs were also collected (from 5 optical-NIR and 3 radio telescopes), in order to fill the gap between the end of the period presented in Raiteri et al. (2001) and the start of the WEBT campaign. The contribution of the southern AGN, 2 arcsec distant from the source, is taken into account. It is found to especially affect the blue part of the optical spectrum when the source is faint. In the optical and near-IR the source has been very active in the last 3 years, although it has been rather faint most of the time, with noticeable variations of more than a magnitude over a few days. In contrast, in the radio bands it appears to have been "quiescent" since early 2000. The major radio (and optical) outburst predicted to peak around February-March 2004 (with a six month uncertainty) has not occurred yet. When comparing our results with the historical light curves, two different behaviours seem to characterize the optical outbursts: only the major events present a radio counterpart. The X-ray spectra obtained by the three EPIC detectors are well fitted by a power law with extra-absorption at z=0.524; the energy index in the 0.2-10 keV range is well constrained: α = 0.645 ± 0.028 and the 1 keV flux density is 0.311 ± 0.008 µJ_y. The analysis of the X-ray light curves reveals that no significant variations occurred during the pointing. In contrast, simultaneous dense radio monitoring with the 100 m telescope at Effelsberg shows a ~ 2-3 % flux decrease in 6-7 h, which, if intrinsic, would imply a brightness temperature well above the Compton limit and hence a lower limit to the Doppler factor δ > 46. We construct the broad-band spectral energy distribution of January 18-19, 2004 with simultaneous radio data from Effelsberg, optical data from the Nordic Optical Telescope (NOT), optical-UV data from the Optical Monitor onboard XMM-Newton, and X-ray data by the EPIC instruments. Particular care is taken to correct data for extinction due to both the Milky Way and the z=0.524 absorber. The resulting SED suggests the existence of a bump in the UV spectral region.

Pian, E., Foschini, L., Beckmann, V., Sillanpää, A., Soldi, S., Tagliaferri, G., Takalo, L., Barr, P., Ghisellini, G., Malaguri, G., Maraschi, L., Palumbo, G.G.C., Treves, A., Courvoisier, T.J-L., Di Cocco, G., Gehrels, N., Giommi, P., Hudec, R., Lindfors, E., Marcowith, A., Nilsson, K., Pasanen, M., Pursimo, T., Raiteri, C.M., Savolainen, T., Sikor, M., Tornikoski, M., Tosti, G., Türler, M., Valtaoja, E., Villata, M., Walter, R.:
INTEGRAL observations of the field of the BL Lacertae object S5 0716+714.
Astronomy and Astrophysics, Vol. 420, pp. 427-431, 2005.
Abstract We have performed observations of the blazar S5 0716+714 with INTEGRAL on 2-6 April 2004. In the first months of 2004, the source had increased steadily in optical brightness and had undergone two outbursts. During the latter outburst, that occurred in March, it reached the extreme level of R = 12.1 mag, which triggered our INTEGRAL program. The target has been detected with IBIS/ISGRI up to 60 keV, with a flux of erg s -1 cm -2 in the 30-60 keV interval, a factor of ~2 higher than observed by the BeppoSAX PDS in October 2000. In the field of S5 0716+714 we have also detected the Flat Spectrum Radio Quasar S5 0836+710 and the two Seyfert galaxies Mkn 3 and Mkn 6. Their IBIS/ISGRI spectra are rather flat, albeit consistent with those measured by BeppoSAX. In the spectrum of Mkn 3 we find some evidence of a break between ~60 and ~100 keV, reminiscent of the high energy cut-offs observed in other Seyfert galaxies. This is the first report of INTEGRAL spectra of weak Active Galactic Nuclei.

Ogle, P.M., Davis, S.W., Antonucci, R.R.J., Colbert, J.W., Malkan, M.A., Page, M.J., Sasseen, T.P., Tornikoski, M.:
Multiwavelength observations of radio galaxy 3C 120 with XMM-Newton.
Astrophysical Journal, Vol. 618, pp. 139-154, 2005.
Abstract We present XMM-Newton observations of the radio galaxy 3C 120. Contemporaneous radio, millimeter-wave, and optical data provide additional constraints on the spectral energy distribution and physical state of the active galactic nucleus. The hard X-ray spectrum contains a marginally resolved Fe I K emission line with FWHM = 9000 ± 3000 km s-1 and an equivalent width of 57 ± 7 eV. The line arises via fluorescence in a broad-line region with covering fraction of 0.4. There is no evidence of relativistically broad Fe K, contrary to some previous reports. An excess of 0.32 keV soft X-ray continuum over an extrapolation of the hard X-ray power law may arise in a disk corona. A break in the X-ray spectrum below 0.6 keV indicates an excess neutral hydrogen column density of NH = (1.01.6) × 1021 cm-2. However, the neutral absorber must have an oxygen abundance of <1/40 of the solar value to explain the absence of an intrinsic or intervening O I edge. There is no ionized absorption in the soft X-ray spectrum, and we do not detect previously claimed O VIII absorption from the intervening intergalactic medium. Radio observations at 37 GHz show a fast, high-frequency flare beginning near the time of the XMM-Newton observation, which has no obvious effect on the X-ray spectrum. The X-ray spectrum, including the soft excess, became harder as the X-ray flux decreased, with an estimated pivot energy of 40 keV. The UV and soft X-ray fluxes are strongly correlated over the 120 ks duration of the XMM-Newton observation. This is qualitatively consistent with Comptonization of UV photons by a hot corona.

Torniainen, I., Tornikoski, M., Teräsranta, H., Aller, M.F., Aller, H.D.:
Long term variability of inverted-spectrum sources and candidates.
Astronomy and Astrophysics Vol. 435, pp. 839-856, 2005
Abstract We have combined new data from our observing campaigns and data from the literature to construct the radio continuum spectra for a sample of mostly quasar-type high peaking gigahertz-peaked spectrum (GPS) source candidates. We have also studied the spectra and variability of so called "bona fide" GPS sources and other inverted-spectrum sources from the literature. For many of our sample sources we now have data spanning over two decades, enabling us to study their long term behaviour. Based on our earlier results we expected to find several new high peaking GPS sources. Instead we found out that even most of the "bona fide" GPS sources cease to adhere to the generic GPS source properties when using these well-sampled long term data sets. In our sample of 35 inverted-spectrum sources from the literature only five seem to be consistent with the GPS properties, and even out of these sources two are too sparsely sampled to firmly make conclusions about their variability. Thirteen of the "bona fide" GPS sources exhibit pronounced activity, which diverges from the low variability expected from these sources. None of our new candidates turned out to have both a convex spectrum and little to no variability, but there is one variable source with a consistently convex spectrum. All the rest have flat spectra, but the upper envelope of the spectrum is clearly convex for four extremely variable sources. Similar continuum spectra with a flat lower envelope and a convex upper envelope are observed for eight previously identified inverted-spectrum sources. According to this study the genuine quasar-type GPS sources are rare but there is a large number of highly variable sources that can have a convex spectrum peaking at high radio frequencies (up to ca. 100 GHz) during flares. Many of the GPS sources from the literature have too easily been classified as GPS sources based on too sparse data, and studying the long term variability is essential for identifying the sources with consistently convex continuum spectra.

Teräsranta, H., Achren, J., Hanski, M., Heikkilä, J., Holopainen, J., Joutsamo, O., Juhola, M., Karlamaa, K., Katajainen, S., Keinänen, P., Koivisto, P., Koskimies, M., Könönen, P., Lainela, M., Lähteenmäki, A., Mäkinen, K., Niemelä, T., Nurmi, P., Pursimo, T., Rekola, R., Savolainen, T., Tornikoski, M., Torppa, J., Valtonen, T., Varjonen, N., Vilenius, E., Virtanen, J., Wiren, S.:
Twenty years monitoring of extragalactic sources at 22, 37 and 87 GHz.
Astronomy and Astrophysics, Vol. 427, pp. 769-771, 2004.
Abstract Long term monitoring results from mid 1995 to the end of 2000 of quasar observations at 22, 37 and 87 GHz done at the Metsähovi radio observatory are presented. Approximately 15 700 observations are published here

Villata, M., Raiteri, C.M., Aller, H.D., Aller, M.F., Teräsranta, H., Koivula, P., Wiren, S., Kurtanidze, O.M., Nikolashvili, M.G., Ibrahimov, M.A., Papadakis, I.E., Tosti, G., Hroch, F., Takalo, L.O., Sillanpää, A., Hagen-Thorn, V.A., Larionov, V.M., Schwartz, R.D., Basler, J., Brown, L.F., Balonek, T.J.
The WEBT campaigns on BL Lacertae, Time and cross-relation analysis of optical and radio light curves 1968-2003.
Astronomy and Astrophysics, Vol. 424, pp. 497-507, 2004.
AbstractThe Whole Earth Blazar Telescope (WEBT) collaboration has collected a large amount of optical and radio data on BL Lacertae in the last years, which, when added to literature data, allow to construct well-sampled light curves of the source from 1968 to the end of 2003. These optical and radio data are here analysed with three statistical methods designed for unevenly-sampled data trains in order to search for possible periodicities. While the main radio outbursts repeat every ~ 8 years, with a possible progressive stretching of the period, the evidence of an optical periodicity is much less clear. Radio light curves from 4.8 to 37 GHz are well correlated, with variations at the higher frequencies leading the lower-frequency ones by a few weeks for contiguous bands, up to a few months when considering the largest frequency separations. The radio behaviour reveals the presence of two different components, the softer-spectrum one constituting the bulk of the radio emission. On the other hand, the harder component shows itself as radio events which appear enhanced at the higher frequencies and seem to have optical counterparts. Cross-correlation between the optical light curve and radio hardness ratios indicates a radio time delay of more than 3 months. Thus, our analysis suggests a scenario where flux variations propagate towards less and less opaque regions, giving rise to related optical and hard radio events and, in more extended zones, to soft events apparently uncorrelated with the former ones.

Bloom, S.D., Dale, D.A., Cool, R., Dupczak, K., Miller, C., Haugsjaa, A., Peters, C., Tornikoski, M., Wallace, P., Pierce, M.:
An optical survey of the position error contours of unidentified high energy gamma-ray sources at galactic latitude |b| > 20 º.
The Astronomical Journal, Vol. 128, pp. 56-61, 2004.
Abstract We present results from our optical survey of the position error contours ("error boxes") of unidentified EGRET sources at mid-to-high Galactic latitude. It is our intention to search for potential blazars that may have been missed in the original identification process of the three EGRET Catalogs and supplementary publications. We have first searched the error contours of unidentified sources at |b| > 20 for flat-spectrum radio sources using the NASA/IPAC Extragalactic Database. For each such radio source found, we conducted optical searches for counterparts using the Palomar 60 inch (1.5 m) telescope and the University of Wyoming's 2.3 and 0.6 m telescopes. Many of the radio sources have plausible optical counterparts, and spectroscopy will be conducted at a later date to determine which of these sources are quasars or active galaxies. Results show that several sources are optically variable and/or have flat or inverted radio-to-millimeter spectra and are thus potential blazars.

Heidt, J., Tröller, M., Nilsson, K., Jäger, K., Takalo, L., Rekola, R., Sillanpää, A.:
Evolution of BL Lacertae host galaxies.
Astronomy and Astrophysics, Vol. 418, pp. 813-825, 2004.
Abstract: We present and discuss deep, high-resolution I-band images of 24 BL Lac objects between z = 0.3 and 1.3 taken with the Nordic Optical Telescope (NOT) and the ESO-NTT and VLT telescopes. In addition, new redshifts for the BL Lac objects PKS 0406+121, PKS 0426-380 and PKS 1519273 are reported.
In 17/24 (71%) of the BL Lac objects, we detected an underlying nebulosity, in 11/17 for the first time. We assigned the underlying nebulosity to the BL Lac host galaxy in 11 cases spanning the redshift range z = 0.3-1 . The remaining 6 BL Lac objects have either intervening galaxies (S4 0218+35, PKS 0426-380), no redshift (MH 2133-449) or are probably misidentified (Q 0230+3429, B2 0937+26, MS 2347.4+1924).
Restricting ourselves to the 11 BL Lac objects ((z) = 0.6), where a core and host galaxy was detected, we find that their host galaxies are luminous (M_I = 25.2 + 0.8) and large (r_e = 10.5 7 kpc). They are on average about 0.6 mag brighter than BL Lac host galaxies at z ~ 0.3 indicative of evolution, whereas their half-light radii are similar.
By combining our data with literature data at lowredshift and applying evolutionary models to them, we show that the properties of the host galaxies of BL Lac objects up to z ~ 1 are compatible with passively evolving elliptical galaxies formed at a redshift of z ~ 2 (13 Gyrs ago in our adopted cosmology).
Our results, however, are affected by an unavoidable luminosity bias and need to be confirmed. Future prospects are described. If they could be confirmed, host galaxies of low-luminosity radio-loud AGN (BL Lac/FR I) have very similar properties to the hosts of radio-quiet QSOs and high-luminosity radio-loud AGN (radio-loud QSO/FR II) over a wide redshift range. This supports the picture of the "Grand Unification" in which AGN activity is a transient phenomenon in galaxy evolution.

Ciprini, S., Tosti, G., Teräsranta, H., Aller, H.D.:
Radio-optical flux behavior and spectral energy distribution of the intermediate blazar GC 0109+224.
Monthly Notices of the R.A.S., Vol. 348, pp. 1379-1387, 2004.
Abstract: About 20 years of radio observations of the BL Lac object GC 0109+224 (S2 0109+22, RGB J0112+227) in five bands (from 4.8 to 37 GHz) are presented and analysed together with optical data. Over the past 10 years this blazar has exhibited enhanced activity. There is only weak correlation between radio and optical flare delays, usually protracted on longer time-scales in the radio with respect to the optical. In some cases no radio flare counterpart was observed for the optical outbursts. The radio variability, characterized by peak superposition, shows hints of some characteristic time-scales (around the 3 - 4 yr), and a fluctuation mode between the flickering and the shot noise. The reconstructed spectral energy distribution, poorly monitored at high energies, is preliminarily parametrized with a synchrotronself-Compton description. The smooth synchrotron continuum, peaked in the near-infraredoptical bands, strengthens the hypothesis that this source could be an intermediate blazar. Moreover, the intense flux in millimetre bands, and the optical and X-ray brightness, might suggest a possible detectable gamma-ray emission.

Ciaramella, A., Bongardo, C., Aller, H.D., Aller, M.F., De Zotti, G., Lähteenmäki, A., Longo, G., Milano, L., Tagliaferri, R., Teräsranta, H., Tornikoski, M., Urpo, S.:
A multifrequency analysis of radio variability of blazars.
Astronomy and Astrophysics,, Vol. 419, pp. 485-500, 2004.
Abstract:We have carried out a multifrequency analysis of the radio variability of blazars, exploiting the data obtained during the extensive monitoring programs carried out at the University of Michigan Radio Astronomy Observatory (UMRAO, at 4.8, 8, and 14.5 GHz) and at the Metsähovi Radio Observatory (22 and 37 GHz). Two different techniques detect, in the Metsähovi light curves, evidence of periodicity at both frequencies for 5 sources ( 0224+671, 0945+408, 1226+023, 2200+420, and 2251+158). For the last three sources, consistent periods are found also at the three UMRAO frequencies and the Scargle (1982) method yields an extremely low false-alarm probability. On the other hand, the 22 and 37 GHz periodicities of 0224+671 and 0945+408 (which were less extensively monitored at Metsähovi and for which we get a significant false-alarm probability) are not confirmed by the UMRAO database, where some indications of ill-defined periods of about a factor of two longer are retrieved. We have also investigated the variability index, the structure function, and the distribution of intensity variations of the most extensively monitored sources. We find a statistically significant difference in the distribution of the variability index for BL Lac objects compared to flat-spectrum radio quasars (FSRQs), in the sense that the former objects are more variable. For both populations the variability index steadily increases with increasing frequency. The distribution of intensity variations also broadens with increasing frequency, and approaches a log-normal shape at the highest frequencies. We find that variability enhances by 20-30% the high frequency counts of extragalactic radio-sources at bright flux densities, such as those of the WMAP and PLANCK surveys. In all objects with detected periodicity we find evidence for the existence of impulsive signals superimposed on the periodic component.

Böttcher, M., Marscher, A.P., Ravasio, M., Villata, M., Raiteri, C.M., Aller, H.D., Aller, M.F., Teräsranta, H., Mang, O., Tagliaferri, G., Aharonian, F., Krawczynski, H., Kurtanidze, O.M., Nikolashvili, G., Ibrahimov, M.A., Papadakis, I.E., Tsinganos, K., Sadakane, K., Okada, N., Takalo, L.O., Sillanpää, A., Tosti, G., Ciprini, S., Frasca, A., Marilli, E., Robb, R., Noble, J.C., Jorstad, S.G., Hagen-Thorn, V.A., Larionov, V.M., Nesci, R., Maesano, M., Schwartz, R.D., Basler, J., Gorham, P.W., Iwamatsu, H., Kato, T., Pullen, C., Benitez, E., de Diego, J.A., Moilanen, M., Oksanen, A., Rodriquez, D., Sadun, A.C., Kelly, M., Carini, M.T., Miller, H.R., Catalano, S., Dultzin-Hacyan, D., Fan, J.H., Ghisellini, G., Ishioka, R., Karttunen, H., Keinänen, P., Kydryavtseva, N.A., Lainela, M., Lanteri, L., Larionova, E.G., Matsumoto, K., Mattox, J.R., McHardy, I., Montagni, F., Nucciarelli, G., Ostorero, L., Papamastorakis, J., Pasanen, M., Sobrito, G., Uemura, M.:
Astrophyscal Journal, Vol. 596, pp. 847-859, 2003.
Abstract: BL Lacertae (BL Lac) was the target of an extensive multiwavelength monitoring campaign in the second half of 2000. Simultaneous or quasi-simultaneous observations were taken at radio (University of Michigan RAdio Astronomy Observatory and Metsähovi Radio Telescope) and optical (Whole Earth Blazar Telescope (WEBT) collaborations) frequencies., in X-rays (BeppoSAX and RXTE), and at very high energy gamma rays (HEGRA). The WEBT optical campaign achieved an unprecedented time coverage, virtually continuous over several 10-20 hr segments. It revealed intraday variability on timescales of ~ 1.5 hr and evidence for spectral hardening associated with increasing optical flux. During the campaign, BL Lac underwent a major transition from a rather quiescent state prior to 2000 September, to a flaring state for the rest of the year. This was also evident in the X-ray activity of the source. BeppoSAX observations on July 26/27 revealed a rather low X-ray flux and a hard spectrum while a BeppoSAX pointing on Oct. 31 - Nov. 2, 2000, indicated significant variability on time scales of > a few hours, and provided evidence for the synchrotron spectrum extending out to ~ 10 keV during that time. During the July 26/27 observations, there is a tantalizing, though not statistically significant, indication of a time delay of ~ 4 - 5 hr between the BeppoSAX and the R-band light curve. Also, low-significance detection of a timedelay of 15 d between the 14.5 GHz and the 22 GHz radio light curves is reported. Several independent methods to estimate the co-moving magnetic field in the source are presented, suggesting a value of ~ 2e_B^2/7 G, where e_B is the magnetic-field equipartition factor w.r.t. the electron energy density in the jet.

Rantakyrö, F.T., Wiik, K., Tornikoski, M., Valtaoja, E., Bååth, L.B.:
Multifrequency interferometer and radio continuum monitoring observations of CTA 102.
Astronomy and Astrophysics, Vol. 405, pp. 473-485, 2003.
Abstract: This paper represents the work of several years of observation of CTA 102 with both single dish telescopes and interferometric arrays, covering wavelengths from 1.2 cm to 1.3 mm. The resolution of the maps covers an order of magnitude from 0.5 mas to 50 µas. The images presented demonstrate the rapid structural changes in this source. These rapid structural changes correlates with the outbursts seen in the total flux, turnover frequency and in the spectral index. We have calculated the Brightness Temperatures of the components (T_B directly from the determined component sizes and also using the logarithmic variability amplitudes and timescales to calculate the T_Bs. Both the methods yielded measurements of source frame T_Bs no higher than ~a few x 10¹² K. We find that the observed average proper motion is ~0.4 ± 0.07 mas/yr, which corresponds to an apparent transverse velocity of 11 ± 2 c.

Larsson, B., Liseau, R., Bergman, P., Black, J.H., Buat, V., Curry, C.L., Encrenaz, P., Falgarone, E., Fich, M., Frisk, U., Gerin, M., Gregersen, E.M., Harju, J., Hjalmarson, Å., Kwok, S., Liljeström, T., Mitchell, G.F., Nordh, L.H. Olberg, M., Olofsson, G., Ristorcelli, I., Tothill, N.H.F., Wilson, C.D.:
First NH₃ Detection of the Orion Bar.
Astronomy and Astrophysics Letters, Vol. 402, pp. L69-L72, 2003.
Abstract Odin has successfully observed three regions in the Orion A cloud. i.e. OriKL, OriS and the Orion Bar, in the 572,5 GHz rotational ground state line of ammonia ortho-NH₃ (J, K) = 1.0 -> (0.0), and the result for the Orion Bar represents the first detection in an ammonia line. Several velocity components are present in the data. Specifically, the observed line profile from the Orion Bar can be decomposed into two components, which are in agreement with observations in high-J CO lines by Wilson et al. (2001). Using the source model for the Orion Bar by these authors, our Odin observations implies a total ammonia abundance of NH₃/H₂ = 5 x 10^-9.

Wilson, C.D., Mason, A., Gregersen, E., Bergman, P., Black, J.H., Booth, R., Buat, V., Curry, C.L., Encrenaz, P., Falgarone, E., Feldman, P., Fich, M., Frisk, U., Gerin, M., Harju, J., Hasegawa, T., Heikkilä, A., Hjalmarson, Å., Juvela, M., Kwok, S., Larsson, B., Liljeström, T., Liseau, R., Mitchell, G., Nordh, L., Olberg, M., Olofsson, H., Olofsson, G., Plume, R., Ristorcelli, I., Sandqvist, Å., Tothill, N.:
Submillimeter Emission from Water in the W3 Region.
Astronomy and Astrophysics Letters, Vol. 402, pp. L59-L62, 2003.
Abstract Using the Odin satellite, we have mapped the submillimeter emission from the 1₁₀ - 1₀₁ transition of ortho-water in the W3 star-forming region. A 5' x 5' map of the W3 IRS4 and W3 IRS5 region reveals strong water lines at half the positions in the map. The relative strength of the Odin lines compared to previous observations by SWAS suggests that we are seeing water emission from an extended region. Across much of the map the lines are double-peaked, with an absorption feature at - 39 km s^-1; however, some positions in the map show a single strong line at -43 km s^-1. We interpret the double-peaked lines as arising from optically thick, self-absorbed water emission near the W3 IRS5, while the narrower blue-shifted lines originate in emission near W3 IRS4. In this model, the unusual appearance of the spectral lines across the map results from a coincidental agreement in velocity between the emission near W3 IRS4 and the blue peak of the more complex lines near W3 IRS5. The strength of the water lines near W3 IRS4 suggests we may be seeing water emission enhanced in a photon-dominated region.

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Jorstad, S.G., Marscher, A.P., Lister, M.L., Stirling, A.M., Teräsranta, H.:
Measurement of the VLBI Core Proper Motion of OJ 287 at 43 GHz.
Bulletin of the American Astronomical Society , Vol. 34, 4, p. 1180, 2003.
Abstract: We observed the BL Lac object OJ 287 and nearby in angle extragalactic radio source J0856+211 with the VLBA at 10 epochs from April 1999 to April 2001. Using these data, we measure position of the VLBI core of OJ 287 at 43 GHz relative to the phase-referencing source with an accuracy of about 0.05 mas. During this period OJ 287 underwent two prominent flares at 22/37 GHz according to Metsähovi Radio Observatory data. The outbursts are accompanied by ejections of superluminal components. We determine whether the VLBI core remains stationary or moves as outbursts occur and as superluminal knots progress downstream.

Pian, E., Falomo, R., Hartman, R.C., Maraschi, L., Tavecchio, F., Tornikoski, M., Treves, A., Urry, C.M., Ballo, L., Mukherjee, R., Scarpa, R., Thompson, D.J., Pesce, J.E.:
Broad-band continuum and line emission of the gamma-ray blazar PKS 0537-441.
Astronomy and Astrophysics, Vol. 392, pp. 407-415, 2002.
Abstract: PKS 0537-441, a bright gamma-ray emitting blazar, was observed at radio, optical, UV and X-ray frequencies during various EGRET pointings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all wavelengths. BeppoSAX observations made in 1998, non-simultaneously with exposures at other frequencies allow us to characterize precisely the spectral shape of the high energy blazar component, which we attribute to inverse Compton scattering. The optical-to-gamma-ray spectral energy distributions at the different epochs show that the gamma-ray luminosity dominates the bolometric output. This, together with the presence of optical and UV line emission, suggests that, besides the synchrotron self-Compton mechanism, the Compton upscattering of photos external to the jet (e.g., in the broad line region) may have a significant role in the production of high energy radiation. The multiwavelength variability can be reproduced by changes of the plasma bulk Lorenz factor. The spectrum secured by IUE in 1995 appears to be partially absorbed shortward of ~ 1700 Å. However, this signature is not detected in the HST spectrum taken during a lower state of the source. The presence of intervening absorbers is not supported by optical imaging and spectroscopy of the field.

Tornikoski, M., Lähteenmäki, A., Lainela, M., Valtaoja, E.:
Possible Identifications for Southern EGRET Sources.
Astrophysical Journal, Vol. 579, pp. 136-147, 2002.
Abstract: We have made total flux density observations at high radio frequencies (90 and 230 GHz) of 12 southern AGNs that were classified as possible EGRET identifications in the Third EGRET Catalog. Our observations confirm the blazar nature of five of them. We have also studied sources that we considered good candidates for AGN counterparts of previously unidentified EGRET sources that had not been observed in the millimeter domain before. Four of them showed millimeter range activity that may be related to their gamma-ray activity, making them good candidates for the EGRET source identification.

Savolainen, T., Wiik, K., Valtaoja, E., Jorstad, S.G., Marscher, A.P.:
Connections between millimetre continuum variations and VLBI structure in 27 AGN.
Astronomy and Astrophysics Vol. 394, pp. 851-861, 2002.
Abstract: We compare total flux density variations in 27 gamma-ray blazars with structural changes in their parsec-scale jets using multi-epoch VLBA observations at 22 and 43 GHz together with data from the Metsähovi quasar monitoring program at 22 and 37 GHz. There is a clear connection between total flux density outbursts and VLBI components emerging into the jet. For essentially every new moving VLBI component, there is a coincident total flux density flare, with evolution similar to that of the component. Furthermore, extrapolated ejection times of the new VLBI components correspond to the beginnings of associated flares. Our results suggest that it is possible to explain all the radio variations as shocks propagating down the jet. A large fraction of the shocks grow and decay within the innermost few tenths of a milliarcsecond and therefore we see them only as "core flares" in the VLBI images. However, with present data we cannot exclude the possibility that the core itself also brightens (and thus contributes to the flare) as a shock passes through it.

Salvi, N.J., Page, M.J., Stevens, J.A., Wu, K., Mason, K.O., Aller, M.F., Aller, H.D., Teräsranta, H., Romero-Comenero, E., Cordova, F.A., Priedhorsky, W.C.:
Correlated multiwavelength emission from the X-ray-bright Seyfert galaxy III Zw 2.
Monthly Notices of the Royal Astronomical Society, Vol. 335, pp. 177-188. 2002
Abstract: The X-ray-bright Seyfert 1 galaxy III Zw 2 was observed with XMM-Newton in 2000 July. Its X-ray spectrum can be described by a power law of photon index GAMMA = 1.7 and an extremely broad (FWHM ~ 140 000 km s¹) Fe Kalpha line at 6.44 keV. The iron line has an equivalent width of ~800 eV. To study the long-term X-ray behaviour of the source we have analysed 25 yr of data, from 1975 to 2000. There is no evidence of significant intrinsic absorption within the source or of a soft X-ray excess in the XMM or archival data. We do not detect rapid X-ray variability (a few x 10 ³s) during any of the individual observations; however, on longer timescales (a few years) the X-ray light curve shows 10-fold flux variations. We infer a black hole mass of ~10⁹ M_O (from Hbeta FWHM) for III Zw 2 which is much higher than some previous estimates.
A comparison of X-ray variability with light curves at other wavelengths over a 25-yr period reveals correlated flux variations from radio to X-ray wavelengths. We interpret the variable radio to optical emission as a synchrotron radiation, self-absorbed in the radio/millimetre region, and the X-rays mainly as a result of Compton up-scattering of low-energy photons by the population of high-energy electrons that give rise to the synchrotron radiation.

Greve, A., Könönen, P., Graham, D.A., Wiik, K., Krichbaum, T.P., Conway, J., Rantakyrö, F., Urpo, S., Grewing, M., Booth, R.S., John, D., Navarro, S., Mujunen, A., Ritakari, J., Peltonen, J., Sjöman, P., Oinaskallio, E., Berton, M.:
147 GHz VLBI observations: detection of fringes on the 3100 km baseline Metsähovi - Pico Veleta.
Astronomy and AstrophysicsVol. 390, pp. L19-L22, 2002.
Abstract: We report a successful VLBI observation at 147 GHz (2.1 mm) on the 3100 km long baseline between the telescopes at Metsähovi (Finland) and Pico Veleta (Spain). The sources 3C 273B and 3C 279 were detected with a SNR of ~ 10. For these sources we estimate that 25-30 % of the total flux is detectable as correlated flux on the 3100 km baseline, which geves at 147 GHz a lower limit of the brightness temperature of the inner VLBI jet region of ~ 1x10¹⁰K.

Marscher, A.P., Jorstad, S.G., Gómez, J-L., Aller, M.F., Teräsranta, H., Lister, M.L., Stirling, A.M.:
Observational evidence for the accretion-disk origin for a radio jet in an active galaxy.
Nature Vol. 417, pp. 625-627, 2002.
Abstract: Accretion of gas onto blackholes is thought to power the relativistic jets of material ejected from active galactic nuclei (AGN) and the 'microquasars' located in our Galaxy^1-3. In microquasars, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decreases in the X-ray fluxes¹. This establishes a direct observational link between the black hole and the jet: the X-ray dip is probably caused by the disappearance of a section of the inner accretion disk⁴ as it falls past the event horizon, while the remainder of the disk section is ejected into the jet, creating the appearance of a superluminal bright spot⁵. No such connection has hitherto been established for AGN, because of insufficient multi-frequency data. Here we report the results of three years of monitoring the X-ray and radio emission of the galaxy 3C120. As has been observed for microquasars, we find that dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. The mean time between X-ray dips appears to scale roughly with the mass of the black hole, although there are at present only a few data points.

Koistinen, O., Lahtinen, J., Hallikainen, M.:
Comparison of analog continuum correlators for remote sensing and radio astronomy.
IEEE Transactions on Instrumentation Measurement, Vol. 51, No 2, 2002.
Abstract:Two different designs of analog correlators for radiometry are compared in this paper. A continuum correlator based on a microwave nonlinear device is a simple and inexpensive way to detect wide-band polarized signals. Analysis and extensive measurements including linearity, dynamic range, amplitude respons, phase balance, and stability are presented, and the suitability of the designs for microwave radiometry is discussed. Both correlators showed nearly ideal preformance. A novel method for determining the correlator degradation factor is applied

Lyytinen, J., Johansson, P., Esko, E., Hackman, T., Hall, D.S., Henry, G.W., Kontinen, S., Könönen, P., Maisala, S., Palviainen, A., Ryynänen, K.:
Time series analysis of V511 Lyrae photometry.
Astronomy and Astrophysics, Vol. 383, pp. 197-201, 2002.
Abstract: Our time series analysis of sixteen BV light curves of the chromospherically active binary V511 Lyr confirmed the 2.^d 7 rotation period uniquely. The seasonal periodicity changes of 3.8 % indicated the presence of detectabel surface differential rotation. The significant 2.^d 67455 periodicity in the light curve minimum epochs suggested that the strongest starspot formation in V511 Lyr was concentrated on one stable active longitude.

Raiteri, C.M., Villata, M., Aller, H.D., Aller, M.F., Heidt, J., Kurtanidze, O.M., Lanteri, L., Maesano, M., Massaro, E., Montagni, F., Nesci, R., Nilsson, K., Nikolashvili, M.G., Nurmi, P., Ostorero, L., Pursimo, T., Rekola, R., Sillanpää, A., Takalo, L.O., Teräsranta, H., Tosti, G., Balonek, T.J., Feldt, M., Heines, A., Heisler, C., Hu, J., Kidger, M., Mattox, J.R., McGrath, E.J., Pati, A., Robb, R., Sadun, A.C., Shastri, P., Wagner, S.J., Wei, J., Wu, X.:
Optical and radio variability of the BL Lacertae object AO 0235+16: A possible 5-6 year periodicity.
Astronomy and Astrophysics, Vol. 396, pp. 396-412, 2001.
Abstract: The BL Lacertae object AO 0235+16 is well known for its extreme optical and radio variability. New optical and radio data have been collected in the last four years by a wide international collaboration, which confirm the intense activity of this source: on the long term, overall variations of 5 mag in the R band and up to a factor 18 in the radio fluxes were detected, while short-term variability up to 0.5 mag in a few hours and 1.3 mag in one day was observed in the optical band. The optical data also include the results in the Whole Earth Blazar Telescope (WEBT) first-light campaign organized in November 1997, involving a dozen optical observatories. The optical spectrum is observed to basically steepen when the source gets fainter. We have investigated the existence of typical variability time scales and of possible correlations between the optical and radio emissions by means of visual inspection and Discrete Correlation Function (DCF) analysis. On the long term, the autocorrelation function of the optical data shows a double-peaked maximum at 4100-4200 days (11.2-11.5 years) while a double-peaked maximum at 3900-4200 days (10.7-11.5 years) is visible in the radio autocorrelation functions. The existence of this similar characteristic time scale of variability in the two bands is by itself an indication of optical-radio correlation. A further analysis by means of Discrete Fourier Transform (DFT) technique and folded light curves reveals that the major radio outbursts repeat quasi-regularly with a periodicity of ~5.7 years, i.e. half the above time scale. This period is also in agreement with the occurrence of some of the major optical outburst, but not all of them. Visual inspection and DCF analysis of the optical and radio light curves then reveal that in some cases optical outbursts seem to be simultaneous with radio ones, but in other cases they lead the radio events. Moreover, a deep inspection of the radio light curves suggests that in at least two occasions (the 1992-1993 and 1998 outbursts) flux variations at the higher frequencies may have led those at the lower ones.

Zaitsev, V.V., Kislyakov, A.G., Stepanov, A.V., Urpo, S., Shkelev, E.I.:
Low frequency pulsations of coronal magnetic loops.
Radiophysics and Quantum Electronics, Vol. 44, pp. 36-52, 2001. Abstract: We analyze low-frequency intensity fluctuations of the microwave emission from solar flares at frequencies 22 and 37 GHz. The three microwave bursts of durations of about 1 h observed at the Metsähovi Radio Observatory (Finland) with the time resolution of 0.1 and 0.05 s, are studied. To obtain spectral-temporal characteristics of the low-frequency fluctuations, we apply the Wigner-Ville method, i.e., the time-lag Fourier transform of the "local" autocorrelation function of an analytical signal. As a result, we obtain for the first time the dynamical spectra of the low-frequency fluctuations, which are identified as MHD eigenoscillations of coronal magnetic loops. the features of the dynamical spectra testify that several types of low-frequency pulsations are excited in coronal magnetic loops during solar flares: 1) Fast and slow magnetosonic oscillations with periods of 1-1.5 s and 200-280 s, respectively. Fast magnetosonic oscillations appear as pulse trains of duration 100-200 s and have the positive frequency drift dv/dt = 0.125 Hz/min and the frequency splitting Γ 0.05 Hz; 2) The eigenoscillations of a coronal magnetic loop as an equivalent electric circuit. The period of these oscillations is about 1 s during the initial stage of a microwave burst and increases gradually up to 4 s during the decay stage of the radio emission; and 3) Intensity modulation of the microwave radiation by a periodic pulse sequence with a period of about 1 s at the burst onset and about 2 s at its end. The parameters of thedynamical spectra and identification of the MHD pulsations allow us to obtain information on theloop parameters, such as the ratio of the loop radius to its length (r/L 0.1), the ratio of the gas pressure to the magnetic-field pressure inside the loop (ß ~ 2 ^. 10^-3), the ratio of plasma densities outside and inside the loop, and the electric current in the coronal loop (I ~ 1.5 ^. 10¹² A).

Brajsa, R., Ruzdjak, V., Vrsnak, B., Wöhl, H., Pohjolainen, S., Urpo, S.:
On the rigid component in the solar rotation
Astrophysics and Space Science Library , Vol. 259, pp. 263-266, 2001.
Abstract: A rigid component in the rotation velocity determined by tracking low brightness temperature regions in the microwave regime was found and interpreted in terms of their association rate (39 %) with rigidly rotating "pivot-points".

Mattox, J.R., Hallum, J.C., Marscher, A.P., Marchenko-Jorstad, S., Waltman, E.B., Teräsranta, H., Aller, H.D., Aller, M.F.:
A gamma-ray flare of quasar CTA 26.
The Astrophysical Journal, Vol. 549, pp, 906-914, 2001.
Abstract: During the first 3 years of the Compton Gamma Ray Observatory mission, the blazar CTA 26 was observed 10 times by EGRET and not significantly detected. We report an observation in 1995 when CTA 26 flared to a peak gamma-ray flux of (4.9 ± 1.5) x 10 ^-6 cm^-2 s ^-1 (E > 100 MeV), the third brightest of all EGRET blazars. Following the gamma-ray flare, extensive VLBA and single-dish radio observations were obtained. We find two components of a milliardsecond jet moving with apparent transverse velocities of 12 ± 1 h^-1 c, and 5 ± 2 h^-1 c (H_o = 100 h km s^-1 Mpc^-1, q _o = 0.1). The position angle of VLBI components appears to change with time. The slowest VLBI component's motion is consistent with ejection at the time of the 1995 gamma-ray flare. A weak radio flare is also seen in Metsähovi millimeter radio monitoring data, peaking within weeks of the gamma-ray flare.

Riehokainen, A., Urpo, S., Valtaoja, E., Makarov, V.I., Makarova, L.V., Tlatov, A.G.:
Millimeter-radio, SOHO/EIT 171 Å features and the polar faculae in polar zones of the Sun.
Astronomy and Astrophysics, Vol. 366, pp. 676-685, 2001.
Abstract: In this work we study different manifestations of activity in the polar zones of the Sun in order to gain understanding on the phenomenon of enhanced radio temperature regions (ETR) at high solar latitudes. We have obtained simultaneous radio and optical data during 9 days in 1997. The radio data from the Metsähovi radio telescope, Finland, consisted of 37 GHz and 87 GHz solar maps. White light observations at the Kisovodsk solar mountain station in Russia were used to measure the coordinates of polar faculae groups in diffuse bright structures. We also compared our data with the 171 Å EUV SOHO/EIT images for the same time periods. We find the ETRs in general coincide with the relatively dark areas seen in the SOHO/EIT images. Bright structures in the SOHO/EIT maps are, in general, encircled by the polar faculae groups and diffuse bright structures visible in white light. Some of the EUV bright structures appear to be bases of solar plumes. Connections between ETRs and polar faculae are complicated; sometimes we see the polar faculae groups distributed over the whole ETR area. Some faint ETRs appear to have no associated polar faculae. However, in general there is a correlation between the ETRs, the polar faculae groups and the bright structures (bases of the plumes and some other features), indicating that they are different manifestations of the same underlying activity. It is possible that magnetic loops in the active areas, traced by the polar faculae, are responsible for the observed radio enhancements.

Teräsranta, H., Urpo, S., Wiren, S., Valtonen, M.:
Search for new flat-spectrum radio sources.
Astronomy and Astrophysics, Vol. 368, pp. 431-439, 2001.
Abstract: 22 GHz continuum observations with the Metsähovi Radio telescope are used to identifying new flat spectrum radio sources selected form lower frequency survey data. The sample is complete to sources with a flux higher than 0.5 Jy at 1.4 GHz, alpha > -0.5 between 1.4 and 4.85 GHz, declination from 0 to +75 degrees and sources more than 20º from the galactic plane. Additional strong sources from the 5 GHz survey were observed to get the sample as complete as possible down to 1.0 Jy at 22 GHz for extrapolation of source counts to lower flux levels. The new flat spectrum sources will be added to our monitoring sample and their duty cycle will be studied for the coming gamma-ray observatories AGILE and GLAST.

Wehrle, A.E., Piner, B.G., Unwin, S.C., Zook, A.C., Xu, W., Marscher, A.P., Teräsranta, H., Valtaoja, E.:
Kinematics of the parsec-scale relativistic jet in quasar 3C 279: 1991-1997.
The Astrophysical Journal Supplement Series, Vol. 133, pp. 297-320, 2001.
Abstract: We present results of long-term high-frequency VLBI monitoring of the relativistic jet in 3C 279, consisting of 18 epochs at 22 GHz from 1991 to 1997 and 10 epochs at 43 GHz from 1995 to 1997. Three major results of this study are apparent spreeds measured for six superluminal components range from 4.8c to 7.5c (H_o = 70 km s^-1) Mpc^-1, q_o = 0.1), variations in the total radio flux are due primarily to changes in the VLBI core flux, and the uniform-sphere brightness temperature of the VLBI core is ~ 1 x 10¹³ K at 22 GHz after 1995, one of the highest direct estimates of a brightness temperature. If the variability brightness temperature measured for 3C 279 by Lähteenmäki & Valtaoja is an actual value and not a lower limit, the the rest-frame brightness temperature of 3C 279 is quite high and limited by inverse Compton effects rather than equipartition. The parsec-scale morphology of 3C 279 consists of a bright, compact VLBI core, a jet component (C4) that moved from ~ 2 to ~ 3.5 mas from the core during the course of our monitoring, and an inner jet that extends from the core to a stationary component, C5, at ~ 1 mas from the core. Component C4 followed a curved path, and we reconstruct its three-dimensional trajctory using polynomial fits to its position versus time. Component C5 faded with time, possibly due to a previous interaction with C4 similar to interactions seen in simulations by Gómes et al. Components in the inner jet are relatively short lived and fade by the time they reach ~ 1 mas from the core. The components have different speeds and position angles from each other, but these differences do not match the differences predicted by the precession model of Abraham & Carrara. Although VLBI components were born about six months prior to each of the two observed gamma-ray high states, the sparseness of the gamma-ray data prevents a statistical analysis of possible correlations.

Hartman, R.C., Böttcher, M., Aldering, G., Aller, H., Aller, M., Backman, D.E., Balonek, T.J., Bertsch, D.L., Bloom, S.D., Bock, H., Boltwood, P., Carini, M.T., Collmar, W., De Francesco, G., Ferrara, E.C., Freudling, W., Gear, W.K., Hall, P.B., Heidt, J., Hughes, P., Hunter, S.D., Jogee, S., Johnson, W.N., Kanbach, G., Katajainen, S., Kidger, M., Kii, T., Koskimies, M., Kraus, A., Kubo, H., Kurtanidze, O., Lanteri, L., Lawson, A., Lin, Y.C., Lisenfeld., U., Madejski, G., Makino, F., Maraschi, L., Marscher, A.P., McFarland, J.C., McHardy, I., Miller, H.R., Nikolashvili, M., Nilsson, K., Noble, J.C., Nucciarelli, G., Ostero, L., Pian, E., Pursimo, T., Raiteri, C.M., Reich, W., Rekola, R., Richter, G.M., Robson, E.I., Sadun, A., Savolainen, T., Sillanpää, A., Smale, A., Sobrito, G., Sreekumar, P., Stevens, J.A., Takalo, L.O., Tavecchio, F., Teräsranta, H., Thompson, D.J., Tornikoski, M., Tosti, G., Ungerechts., H., Urry, C.M., Valtaoja, E., Villata, M., Wagner, S.J., Wehrle, A.E., Wilson, J.W.:
Multi-Epoch multiwavelength spectra and models for Blazar 3C 279.
The Astrophysical Journal, Vol. 553, pp. 683-694, 2001.
Abstract: Of the blazars detected by EGRET in GeV gamma-rays, 3C 279 is not only the best observed by EGRET but also one of the best monitored at lower frequencies. We have assembled 11 spectra, from GHz radio through GeV gamma-rays, from the time intervals of EGRET observations. Although some of the data have appeared in previous publications, most are new, including data taken during the high states in early 1999 and early 2000. All of the spectra show substantial gamma-ray contribution to the total luminosity of the object; in a high state, the gamma-ray luminosity dominates over that at other frequencies by a factor of more than 10. There is no clear pattern of time correlation; different bands do not always rise and fall together, even in the optical, X-ray , and gamma -ray bands. The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton plus external Compton gamma -ray production. Spectral variability of 3C 279 is consistent with variations of the bulk Lorentz factor of the jet, accompanied by changes in the spctral shaape of the electron distribution. Our modeling results are consistent with the UV spectrum of 3C 279 being dominated by accretion disk radiation during times of low gamma-ray intensity.

Tornikoski, M., Jussila, I., Johansson, P., Lainela, M., Valtaoja, E.:
Radio spectra and variability of gigahertz-peaked spectrum radio sources and candidates.
The Astronomical Journal, Vol. 121, pp. 1306-1318, 2001.
Abstract: We have made long-term, high radio frequency observations of southern and equatorial active galactic nuclei (AGNs). After complementing these data with data from the literature, we have constructed the radio spectra of these sources and searched for sources with inverted spectra in the gigahertz range. We have identified 12 new sources with spectra shapes resembling those of the gigahertz-peaked spectrum (GPS) sources and eight other sources with inverted spectral parts in the gigahertz region. Several of these new GPS-source candidates have high (> GHz) peak frequencies in the observer's frame, and they all exhibit strong long-term variability. We have also studied the variability behaviour of known GPS sources, mainly quasar-type sources. All of the 14 sources included in our sample show moderate to extremely high radio variability, and at least 12 of them are also variable in the millimeter domain. Long-term monitoring of these sources shows that some of them have spectral shapes resembling those of classical variable flat-spectrum sources, indicating that some of these sources have been misidentified as GPS sources when only sparsely sampled data have been available. On the other hand, four of the variable sources show persistent GPS-type spectra at all stages of activity, suggesting that at least some of the GPS sources can be variable.

Brajsa, R., Ruzdjak, V., Vrsnak, B., Whl, H., Pohjolainen, S., Urpo, S.:
Statistical weights and selective height corrections in the determination of the solar rotation velocity.
Solar Physics, Vol. 196, pp 279-297, 2000.
Abstract: Observations of the Sun performed at 37 GHz with the 14-m radio telescope of the Metsähovi Radio Observatory were analyzed. Rotation velocities were determined, tracing Low Temperature Regions (LTRs) in the years 1979-1980, 1981-1982, 1987-1988, and 1989-1991. Statistical weights ascribed to the determined rotation velocities of LTRs, according to the number of tracing days. Measured changes of the rotation velocity during the solar activity cycle, as well as a north-south rotation asymmetry are discussed. The results obtained with and without the statistical weights procedure are compared, and it was found that the statistical significance of the solar differential rotation parameters' changes is higher wen the statistical weights procedure is applied. A selective application of the height correction on LTR's positions has not removed the cycle-related changes nor the north-south asymmetry of the solar rotation measured tracing LTRs. So, projection effects cannot explain these changes. The differential rotation of LTRs is more rigid than the differential rotation obtained tracing magnetic features and measuring Doppler shifts, which can be explained by the association rate of the LTRs' positions with rigidly rotation "pivot points". The observed cycle-related changes and the north-south asymmetry of the rotation velocity of LTRs are consistent with the cycle-related changes and the north-south asymm metry of the solar rotation measured tracing LTRs. So, projection effects cannot explain these changes. The differential rotation of LTRs is more rigid than the differential rotation obtained tracing magnetic features and measuring Doppler shifts, which can be explained by the association rate of the LTRs' positions with rigidly rotation "pivot points". The observed cycle-related changes and the north-south asymmetry of the rotation velocity of LTRs are consistent with the cycle-related changes and the north-south asymmetry of the association rate between LTRs and pivot points.

Zlobec, P., Urpo, S., Vrsnak, B, Brajsa, R., Ruzdjak, V.:
Correlated Radio Bursts observed at m and mm wavelengths.
Hvar Observatory Bulletin, Vol. 24, pp. 41-56, 2000.
Abstract: Characteristics of the bursts that occur almost contemporaneously at metric and millimetric wavelengths are presented. It is found that such events are rather rare. The correlated impulsive bursts observed at 237 MHz and at 37 GHz start in average almost simultaneously (time difference 0.3 ± 2.8 s). The first peaks at 37 GHz are delayed few seconds (3.1 ± 3.0 s) in respect to the 237 MHz peaks, whereas for the bursts maxima the delay is about 1 s in average (1.0 ± 2.7 s). A weak correlation between peak fluxes at 37 GHz and 237 MHz is found. Spectral characteristics of these events indicate electron beams of extremely high energies. the assosiation of the gradual bursts observed at 37 GHz and the phenomena at 237 MHz is not so clear, however in some cases a relationship was established.

Alcaraz J., Alpat, B., Ambrosi, G., Anderhub, H., Ao, L., Arefiev, A., Azzarello, P., Babucci, E., Baldini, L., Basile, M., Barancourt, D., Barao, F., Barbier, G., Barreira, G., Battiston, R., Becker, R., Becker, U., Bellagamba, L., Béné, P., Berdugo, J., Berges, P., Bertucci, B., Biland, A., Bizzaglia, S., Blasko, S., Boella, G., Boschini, M., Bourquin, M., Brocco, L., Bruni, G., Buenerd, M., Burger, J.D., Burger, W.J., Cai, X.D., Camps, C., Cannarsa, P., Capell, M., Casadei, D., Casaus, J., Castellini, G., Cecchi, C., Chang, Y.H., Chen, H.F., Chen, H.S., Chen, Z.G., Chernoplekov, N.A., Chiueh, T.H., Chuang, Y.L., Cindolo, F., Commichau, V., Contin, A., Christinziani, M., da Cunha, J.P., Dai, T.S., Deus, J.D., Dinu, N., Djambazov, L., D'Antone, I., Dong, Z.R., Emonet, P., Engelberg, J., Eppling, F.J., Eronen, T., Esposito, G., Extermann, P., Favier, J., Fiandrini, E., Fisher, P.H., Fluegge, G., Fouque, N., Galaktionov, Yu., Gervasi, M., Giusti, P., Grandi, D., Grimm, O., Gu, W.Q., Hangarter, K., Hasan , A., Hermel, V., Hofer, H., Huang, M.A., Hungerford, W., Ionica, M., Ionica, R., Jongmanns, M., Karlamaa, K., Karpinski, W., Kenney, G., Kenny, J., Kim, W., Klimentov, A., Kossakowski, R., Koutsenko, V., Kraeber, M., Laborie, G., Laitinen, T., Lamanna, G., Laurenti, G., Lebedev, A., Lee, S.C., Levi, G., Levtchenko, P., Liu, C.L., Liu, H.T., Lopes, I., Lu, G., Lu, Y.S., Lübelsmeyer, K., Luckey, D., Lustermann, W., Mana, C., Margotti, A, Mayet, F., McNeill, R.R., Meillon, B., Menichelli, M., Mihul, A., Mourao, A., Mujunen, A., Palmonari, F., Papi, A., Park, I.H., Pauluzzi, M., Pauss, F., Perrin, E., Pesci, A., Pevsner, A., Pimenta, M., Plyaskin, V., Pojidaev, V., Pohl, M., Postolache, V., Produit, N., Rancoita, P.G., Rapin, D., Raupach, F., Ren, D., Ren, Z., Ribordy, M., Richeux, J.P., Riihonen, E., Ritakari, J., Roeser, U., Roissin, C., Sagdeev, R., Sartorelli, G., Schultz von Dratzig, A., Schwering, G., Scolieri, G., Seo, E.S., Shoutko, V., Shoumilov, E., Siedling, R., Son, D., Song, T., Steuer, M., Sun, G.S., Suter, H., Tang, X.W., Ting, Samuel C.C., Ting, S.M., Tornikoski, M., Torsti, J., Trümper, J., Ulbricht, J., Urpo, S., Usoskin, I., Valtonen, E., Vandenhirtz, J.,Velcea, F., Velikhov, E., Verlaat, B., Vetlitsky, I., Vezzu, F., Vialle, J.P., Viertel, G., Vite, D., Von Gunten, H., Waldmeier Wicki, S., Wallraff., W., Wang, B.C., Wang, J.Z., Wang, Y.H., Wiik, K., Williams, C., Wu, S.X., Xia, P.C., Yan, J.L., Yan, L.G., Yang, C.G., Yang, M., Ye, S.W., Yeh, P., Xu, Z.Z., Zhang, H.Y., Zhang, Z.P., Zhao, D.X., Zhu, G.Y., Zhu, W.Z., Zhuang, H.L., Zichichi, A., Zimmermann, B., Zuccon, P.:
Helium in near Earth orbit.
Physics Letters B, http://hpl3tri1.cern.ch/AMS/Publications/ Vol. 494, pp. 193-202, 2000.
Abstract: The helium spectrum from 0.1 to 100 GeV/nucleon was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. Above the geomagnetic cutoff the spectrum is parameterized by a power law. Below the geomagnetic cutoff a second helium spectrum was observed. In the second helium spectra over the energy range 0.1 to 1.2 GeV/nucleon the flux was measured to be (6.3 ± 0.9) x 10^-3 (m² sec sr)^-1 and more than ninety percent of the helium was determined to be ³He (at the 90 % CL). Tracing helium from the second spectrum shows that about half of the ³He travel for an extended period of time in the geomagnetic field and that they originate from restricted geographic regions similar to protons and positrons.

Tornikoski, M., Lainela, M., Valtaoja, E.:
The high radio frequency spectra and variability of southern flat-spectrum radio sources.
The Astronomical Journal, Vol. 120, pp. 2278-2283, 2000.
Abstract: We have complemented observations of the millimeter spectra (90 and 230 GHz) of a complete sample of Southern flat-spectrum active galactic nuclei. We discuss the overall shape of the radio spectrum sources with unusually high peak frequencies (10-20 GHz). We also discuss the variability behavior in the millimeter domain.

Watson, D., Smith, N., Hanlon, L., McBreen, B., Quilligan, E., Tashiro, M., Metcalfe, L., Doyle, P., Beckmann, Teräsranta, H., Carraminana, A., Guichard, J.:
ASCA and other contemporaneous observations of the blazar B2 1308+326.
Astronomy and Astrophysics, Vol. 364, pp. 43-52, 2000.
Abstract: The high redshift (z = 0.997) blazar B2 1308+326 was observed contemporaneously at x-ray, optical and radio wavelengths in June 1996. The x-ray observations were performed with ASCA. The ASCA results were found to be consistent with reanalysed data from two earlier ROSAT observations. The combined ASCA and ROSAT data reveal an x-ray spectrum that is best fit by a broken power law with absorber model with photon spectral indices of gamma_soft = 3.4_-1.1^+5.1 and gamma_hard = 1.63_-0.09^+0.10 and a break energy at 1.1_-0.4^+0.4 keV in the rest-frame of the blazar. The break in the x-ray spectrum is interpreted, from the shape of the simultaneous broadband spectral energy distribution, to be the emerging importance of inverse Compton (IC) emission which dominates the ASCA spectrum. The faint optical state reported for these observations (m_V = 18.3 ± 0.25) is incompatible with the high synchrotron flux previously detected by ROSAT. The IC emission detected by both ROSAT and ASCA was not significantly affected by the large change in the synchrotron component.

Mg II emission was detected with an equivalent width (W_lamda) of ~ 15 Å, significantly different from previously reported values. The small and variable W_lamda in B2 1308+326 may be due to the highly variable continuum and not intrinsically weak lines in the source. A lower limit on the Doppler boost factor calculated from the contemporaneous data is consistent with expectations for highly polarised quasars and higher than expected for BL Lacs. Absorption at a level of N_H = 3.0 _-0.6^+2.3 x 10²⁰ cm^-2 was detected which is in excess of the Galactic value of N_H = 1.1 x 10²⁰ cm^-2 indicating the possible presence of a foreground absorber. A gravitational microlensing scenario cannot therefore be ruled out for this blazar. No significant variability of timescales of hours was detected in the optical or x-ray data.

B2 1308+326 could be a typical radio-selected BL Lac in terms of peak synchtrotron frequency and optical and radio variability but its high bolometric luminosity variable line emission and higher Doppler boost factor make it appear more like a quasar than a BL Lac. It is suggested that B2 1308+326 be considered as the prototype of this class of composite source.

Takahashi, T., Kataoka, J., Madejski, G., Mattox, J., Urry, C.M., Wagner, S., Aharonian, M., Catanese, M., Chiappetti, L., Coppi, P., Degrange. B., Fossati, G., Kubo, H., Krawczynski, H., Makino, F., Marshall, H., Maraschi, L., Piron, F., Remillard, R., Takahara, F., Tashiro, M., Teräsranta, H., Weekes, T.:
Complex spectral variability from intensive multiwavelength monitoring of Markarian 421 in 1998.
The Astrophysical Journal, Vol. 542, pp. L105-L109, 2000.
Abstract: We conducted a multifrequency campaign for the TeV blazar Markarian 421 in 1998 April. The campaign started from a pronounced high-amplitude flare recorded by BeppoSAX and Whipple; the ASCA observation started 3 days later. In the X-ray data we detected multiple flares occurring on timescales of about 1 day. ASCA data clearly reveal spectral variability. The comparison of the data from ASCA, the Extreme Ultraviolet Explorer, and the Rossi X-ray Timing Explorer indicates that the variability amplitudes in the low-energy synchrotron component are larger at higher photon energies. In TeV gamma-rays, large intraday variations - which were correlated with the X-ray flux - were observed when results from three Cerenkov telescopes were combined. The rms variability of TeV gamma-rays was similar to that observed in hard X-rays, above 10 keV. The X-ray light curve reveals flares that are almost symmetric for most cases, implying that the dominant timescale is the light crossing time through the emitting region. The structure function analysis based on the continuous X-ray light curve of 7 days indicates that the characteristic timescale is ~0.5 days. The analysis of ASCA light curves in various energy bands appears to show both soft (positive) and hard (negative) lags. These may not be real, as systematic effects could also produce these lags,which are all much smaller than an orbit. If the lags of both signs are real, these imply that the particle acceleration and X-ray cooling timescales are similar.

Alcaraz J., Alpat, B., Ambrosi, G., Anderhub, H., Ao, L., Arefiev, A., Azzarello, P., Babucci, E., Baldini, L., Basile, M., Barancourt, D., Barao, F., Barbier, G., Barreira, G., Battiston, R., Becker, R., Becker, U., Bellagamba, L., Béné, P., Berdugo, J., Berges, P., Bertucci, B., Biland, A., Bizzaglia, S., Blasko, S., Boella, G., Boschini, M., Bourquin, M., Brocco, L., Bruni, G., Buenerd, M., Burger, J.D., Burger, W.J., Cai, X.D., Camps, C., Cannarsa, P., Capell, M., Casadei, D., Casaus, J., Castellini, G., Cecchi, C., Chang, Y.H., Chen, H.F., Chen, H.S., Chen, Z.G., Chernoplekov, N.A., Chiueh, T.H., Chuang, Y.L., Cindolo, F., Commichau, V., Contin, A., Crespo, P., Christinziani, M., da Cunha, J.P., Dai, T.S., Deus, J.D., Dinu, N., Djambazov, L., D'Antone, I., Dong, Z.R., Emonet, P., Engelberg, J., Eppling, F.J., Eronen, T., Esposito, G., Extermann, P., Favier, J., Fiandrini, E., Fisher, P.H., Fluegge, G., Fouque, N., Galaktionov, Yu., Gervasi, M., Giusti, P., Grandi, D., Grim, O., Gu, W.Q., Hangarter, K., Hasan , A., Hermel, V., Hofer, H., Huang, M.A., Hungerford, W., Ionica, M., Ionica, R., Jongmanns, M., Karlamaa, K., Karpinski, W., Kenney, G., Kenny, J., Kim, W., Klimentov, A., Kossakowski, R., Koutsenko, V., Kraeber, M., Laborie, G., Laitinen, T., Lamanna, G., Laurenti, G., Lebedev, A., Lee, S.C., Levi, G., Levtchenko, P., Liu, C.L., Liu, H.T., Lopes, I., Lu, G., Lu, Y.S., Lübelsmeyer, K., Luckey, D., Lustermann, W., Mana, C., Margotti, A, Mayet, F., McNeill, R.R., Meillon, B., Menichelli, M., Mihul, A., Mourao, A., Mujunen, A., Palmonari, F., Papi, A., Park, I.H., Pauluzzi, M., Pauss, F., Perrin, E., Pesci, A., Pevsner, A., Pimenta, M., Plyaskin, V., Pojidaev, V., Pohl, M., Postolache, V., Produit, N., Rancoita, P.G., Rapin, D., Raupach, F., Ren, D., Ren, Z., Ribordy, M., Richeux, J.P., Riihonen, E., Ritakari, J., Roeser, U., Roissin, C., Sagdeev, R., Sartorelli, G., Schultz von Dratzig, A., Schwering, G., Scolieri, G., Seo, E.S., Shoutko, V., Shoumilov, E., Siedling, R., Son, D., Song, T., Steuer, M., Sun, G.S., Suter, H., Tang, X.W., Ting, Samuel, C.C., Ting, S.M., Tornikoski, M., Torsti, J., Trümper, J., Ulbricht, J., Urpo, S., Usoskin, I., Valtonen, E., Vandenhirtz, J.,Velcea, F., Velikhov, E., Verlaat, B., Vetlitsky, I., Vezzu, F., Vialle, J.P., Viertel, G., Vite, D., Von Gunten, H., Waldmeier Wicki, S., Wallraff., W., Wang, B.C., Wang, J.Z., Wang, Y.H., Wiik, K., C., Wu, S.X., Xia, P.C., Yan, J.L., Yan, L.G., Yang, C.G., Yang, M., Ye, S.W., Yeh, P., Xu, Z.Z., Zhang, H.Y., Zhang, Z.P., Zhao, D.X., Zhu, G.Y., Zhu, W.Z., Zhuang, H.L., Zichichi, A., Zimmermann, B.:
Leptons in Near Earth Orbit.
Physics Letters, http://hpl3tri1.cern.ch/AMS/Publications/, Vol. 484, pp. 10-22, 2000.
Abstract: The lepton spectra in the kinetic energy ranges 0.2 to 40 GeV for e^- and 0.2 to 3 GeV for e⁺ were measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at altitudes near 380 km. From the origin of the leptons two distinct spectra were observed: a higher energy spectrum and a substantial second spectrum with positrons much more abundant than electrons. Tracing leptons from the second spectra shows that most of these leptons travel for an extended period of time in geomagnetic field and that e⁺ and e^- originate from two complementary geographic regions.

Alcaraz J., Alpat, B., Ambrosi, G., Anderhub, H., Ao, L., Arefiev, A., Azzarello, P., Babucci, E., Baldini, L., Basile, M., Barancourt, D., Barao, F., Barbier, G., Barreira, G., Battiston, R., Becker, R., Becker, U., Bellagamba, L., Béné, P., Berdugo, J., Berges, P., Bertucci, B., Biland, A., Bizzaglia, S., Blasko, S., Boella, G., Boschini, M., Bourquin, M., Brocco, L., Bruni, G., Buenerd, M., Burger, J.D., Burger, W.J., Cai, X.D., Camps, C., Cannarsa, P., Capell, M., Casadei, D., Casaus, J., Castellini, G., Cecchi, C., Chang, Y.H., Chen, H.F., Chen, H.S., Chen, Z.G., Chernoplekov, N.A., Chiueh, T.H., Chuang, Y.L., Cindolo, F., Commichau, V., Contin, A., Crespo, P., Christinziani, M., da Cunha, J.P., Dai, T.S., Deus, J.D., Dinu, N., Djambazov, L., D'Antone, I., Dong, Z.R., Emonet, P., Engelberg, J., Eppling, F.J., Eronen, T., Esposito, G., Extermann, P., Favier, J., Fiandrini, E., Fisher, P.H., Fluegge, G., Fouque, N., Galaktionov, Yu., Gervasi, M., Giusti, P., Grandi, D., Grim, O., Gu, W.Q., Hangarter, K., Hasan , A., Hermel, V., Hofer, H., Huang, M.A., Hungerford, W., Ionica, M., Ionica, R., Jongmanns, M., Karlamaa, K., Karpinski, W., Kenney, G., Kenny, J., Kim, W., Klimentov, A., Kossakowski, R., Koutsenko, V., Kraeber, M., Laborie, G., Laitinen, T., Lamanna, G., Laurenti, G., Lebedev, A., Lee, S.C., Levi, G., Levtchenko, P., Liu, C.L., Liu, H.T., Lopes, I., Lu, G., Lu, Y.S., Lübelsmeyer, K., Luckey, D., Lustermann, W., Mana, C., Margotti, A, Mayet, F., McNeill, R.R., Meillon, B., Menichelli, M., Mihul, A., Mourao, A., Mujunen, A., Palmonari, F., Papi, A., Park, I.H., Pauluzzi, M., Pauss, F., Perrin, E., Pesci, A., Pevsner, A., Pimenta, M., Plyaskin, V., Pojidaev, V., Pohl, M., Postolache, V., Produit, N., Rancoita, P.G., Rapin, D., Raupach, F., Ren, D., Ren, Z., Ribordy, M., Richeux, J.P., Riihonen, E., Ritakari, J., Roeser, U., Roissin, C., Sagdeev, R., Sartorelli, G., Schultz von Dratzig, A., Schwering, G., Scolieri, G., Seo, E.S., Shoutko, V., Shoumilov, E., Siedling, R., Son, D., Song, T., Steuer, M., Sun, G.S., Suter, H., Tang, X.W., Ting, Samuel, C.C., Ting, S.M., Tornikoski, M., Torsti, J., Trümper, J., Ulbricht, J., Urpo, S., Usoskin, I., Valtonen, E., Vandenhirtz, J.,Velcea, F., Velikhov, E., Verlaat, B., Vetlitsky, I., Vezzu, F., Vialle, J.P., Viertel, G., Vite, D., Von Gunten, H., Waldmeier Wicki, S., Wallraff., W., Wang, B.C., Wang, J.Z., Wang, Y.H., Wiik, K., C., Wu, S.X., Xia, P.C., Yan, J.L., Yan, L.G., Yang, C.G., Yang, M., Ye, S.W., Yeh, P., Xu, Z.Z., Zhang, H.Y., Zhang, Z.P., Zhao, D.X., Zhu, G.Y., Zhu, W.Z., Zhuang, H.L., Zichichi, A., Zimmermann, B.:
Cosmic Protons.
Physics Letters B, http://hpl3tri1.cern.ch/AMS/Publications/Vol. 490, pp 27-35, 2000.
Abstract: The primary proton spectrum in the kinetic energy range 0.2 to 200 GeV was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at an altitude of 380 km. The complete data set combining three shuttle attitudes and including all known systematic effects is presented.

Pyatunina, T.B., Marchenko, S.G., Marscher, A.P., Aller, M.F., Aller, H.D., Teräsranta, H., Valtaoja, E.:
Radio variability of the gamma-ray blazar 0202+149.
Astronomy and Astrophysics, Vol. 358, pp. 451-461, 2000.
Abstract: Analysis of radio light curves of the gamma-ray bright blazar 0202+149 at frequencies of 37, 22, 14.5, 8 and 4.8 GHz during the period 1984-1998 reveals a 4-year cycle of variability with substructure on a shorter time scale about 1.3-yr. The 4.8-37 GHz spectra index if the source gradually increases from -0.04 (T=1990.2) to 0.4(T=1996.6) and during outbursts shows strong variations with a time scale of about 1 year and an amplitude up to ~0.4. VLBI images at 8, 22, and 43 GHz show a core-dominated structure with a faint jet in the northwest direction, which we trace out to 7 mas, with a bent inner part (r < 1 mas) consisting of at least 2 components. The connection of the jet activity with the 4-year cycle of total flux density variability is discussed.

Zaitsev, V.V., Urpo, S., Stepanov, A.V.: Temporal dynamics of Joule heating and DC-electric field acceleration in single flare loop.
Astronomy and Astrophysics, Vol. 357, pp. 1105-1114, 2000.
Abstract: Pulsating and explosive time profiles of mm-wave solar bursts observed at Metsähovi are examined n terms of the energy release in single current-carrying loop. We suppose that the electric current in the loop is driven by photospheric convective flows. The flare occurs due to flute instability provoking the penetration of partially ionized plasma from the chromosphere or prominence into the current channel of a loop and increasing the loop resistance by many orders of magnitude. The feedback of deviation of the loop magnetic field on the energy release rate is taken into account. Joule plasma heating due to current dissipation and electron acceleration in DC electric field are considered. Both processes act simultaneously and are driven by one parameter, the penetration depth of partially ionized plasma into the current-carrying loop. Two regimes of energy release are studied: (i) Pulsating energy release in current-carrying loops with negative radial gradient of gas pressure; (ii) Explosive plus pulsating energy release in a loop with positive radial gradient of gas pressure. One can explain the various time behaviours of the flares, for example, several quasi-periodic pulses, and pulsations with increasing amplitude at pre-flash phase followed by explosive enhancement of the emission at flash phase. The possibility of powerful flare in current-carrying magnetic loop with plasma beta ß << 1 is discussed.

Takalo, L.O., Nilsson, K., Sillanpää, A., Teräsranta, H.: Optical properties of radio source 4C +08.45.
Astronomy and Astrophysics, Vol. 357, pp. 881-883, 2000.
Abstract: We present the first optical observations of the radio source 4C +08.45. It is identified with an elliptical galaxy (R = 15.92) at redshift z = 0.1250, with a comparable companion galaxy (R = 15.36; z = 0.1257) at a projected distance of 34.8 kpc. Both galaxies are normal elliptical galaxies. The galaxy identified with the radio source shows strong emission lines on top of an elliptical galaxy spectrum. The companion shows no emission lines. Based on these observations and the available radio data we believe that 4C +08.45 is a LINER type galaxy.

Brunthaler, A., Falcke, H., Bower, G.C., Aller, M.F., Aller, H.D., Teräsranta, H., Lobanov, A.P., Krichbaum, T.P., Patnaik, A.R.:
III Zw 2, the first superluminal jet in a Seyfert galaxy.
Astronomy and Astrophysics, Vol. 357, pp. L45-L48, 2000.
Abstract: So far all relativistically boosted jets with superluminal motion have only been detected in typical radio galaxies with early type host galaxies. We have now discovered superluminal motion in the Seyfert I galaxy III Zw 2, classified as a spiral. Superluminal motion was first inferred from the spectral evolution of the source and then confirmed by VLBI observations. The lower limit for the apparent expansion speed is 1.25 ± 0.09 c. The fact that the spectral and spatial evolution are closely linked demonstrates that we are dealing with real physical expansion. Prior to this rapid expansion we have seen a period of virtually no expansion with an expansion speed less than 0.04 c. Since III Zw 2 is also part of a sample of so called radio-intermediate quasars (RIQ), it confirms earlier predictions of superluminal motion for this source, based on the argument that RIQs could be relativistically boosted jets in radio-weak quasars and Seyfert galaxies.

Liljeström, T., Gwinn, C.:
Water Masers Diagnosing Postshocked Conditions in W49N.
Astrophysical Journal, Vol. 534, pp. 781-800, 2000.
Abstract: We present spectroscopic results of 146 water maser outbursts in W49N, obtained with the Metsähovi radio telescope at 22 GHz. We found the following characteristics: (1) Inside (outside) the velocity range of dense ambient medium, the increase in flux density during an outburst is typically 10⁴ Jy (10³ Jy) and covers 1 order (2.5 orders) of magnitude. (2) The outburst durations closely trace space velocities of maser features. (3) Nonthermal velocity fluctuations produce variations in the line width during outbursts. (4) There are no correlations between flux density and line width. Combining these data with Gwinn's VLBI results, notably obtained during the same time period and with the same velocity resolution, we were able to fix the free parameters in the shock model of Hollenbach & McKee and the maser model of Elitzur, Hollenbach, & McKee. This enabled a straightforward determination of some 20 shock and maser parameters including, among others, the following typical values: kinetic temperature 350 K, postshock density (3.6-8.7) x 10⁸ cm^-3, water abundance (1-5) x 10^-4, water density (0.9-1.9) x 10⁵ cm^-3, water column density (2.2-7.9) x 10^<19> cm^-2, preshock field strength 0.8-1.6 mG, and total postshock field strength 80-160 mG. A step-by-step presentation of our diagnostic method is given, and the relation between observations and model parameters is discussed. One uniquely powerful outburst feature during 1981-1983, hereafter referred to as the "big flare feature", showed also the narrowest line width (0.5 km s^-1). Observations indicate that the velocity of this feature lies in the plane of the sky, whereas preshock and postshock magnetic fields are directly nearly along the line of sight. Consequently, Alfvenic wave fluctuations along the line of sight, and line width, are minimal, and a very high aspect ratio is achieved. Furthermore, the big flare feature stands out through its low space velocity, higher temperature (480 K), and larger preshock magnetic field strength (8.2 mG). These are naturally explained, if the big flare feature was located closer to the shock front than the other masers.

Valtaoja, E., Teräsranta, H., Tornikoski, M., Sillanpää, A., Aller, M.F., Aller, H.D., Hughes, P.A.:
Radio monitoring of OJ 287 and binary black hole models for periodic outbursts.
Astrophysical Journal, Vol 531, pp. 744-755, 2000.
Abstract: The BL Lac-type active galaxy OJ 287 exhibits a 12 year periodicity with a double-peaked maxima in its optical flux variations. Several models sought to explain this periodicity, the first one firmly established in any active galactic nucleus (AGN), as a result of the orbital motion of a pair of supermassive black holes. In one class of models the orientation of the jets changes in a regular manner, and the optical flaring is due to a consequent increase in the Doppler boosting factor. In another class of models the optical flaring reflects a true increase in luminosity, either due to an enhanced accretion during the pericenter passage or due to a collision between the secondary black hole and the accretion disk of the primary black hole. However, these models have been based solely on the optical data. Here we consider the full radio flux density monitoring data between 8 and 90 GHz from the Michigan, Metsähovi and Swedish-ESO Submillimeter Telescope AGN monitoring programs. We find that the radio flux density and polarization data, as well as the optical polarization data, indicate that the first of the two optical peaks is a thermal flare occurring in the vicinity of the black hole and the accretion disk, while the second one is a synchrotron flare originating in a shocked region down the jet. None of the proposed binary black hole models for OJ 287 offers satisfactory explanations for these observations. We suggest a new scenario, in which a secondary black hole penetrates the accretion disk of the primary during the pericenter passage, causing a thermal flare visible only in the optical regime. The pericenter passage enhances accretion into the primary black hole, leading to increased jet flow and formation of shocks down the jet. These become visible as standard radio and optical synchrotron flares roughly a year after the pericenter passage and are identified with the second optical peaks. In addition to explaining the radio and the optical data, our model eliminates the need for a strong precession of the binary and for an ultramassive (> 10¹⁰ M ) primary black hole. If our interpretation is correct, the next periodic optical flare, a thermal one, should occur around 2006 September 25. Nonthermal, simultaneous optical and radio flares should follow about a year later.

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Engelberg, J., Mujunen, A.:
High rate data link front end design and performance during Alpha Magnetic Spectrometer space shuttle flight, May 1998.
IEEE Aerospace and Electronic, Vol. 15, pp. 33-34, 2000.
Abstract: In June 1998, Metsähovi Radio Observatory participated in a 10-day shuttle mission, STS-91, ground support activity by receiving, archiving, and making available, the so-called High Rate Data (HRD) from Alpha Magnetic Spectrometer (AMS). More information about the mission and the detector can be found in [1]. The particle physics experiment project was led by Nobel Laureate Physicist Samuel C.C. Ting, and built by an international collaboration of over 15 institutes. The goal was to detect antimatter in space. Some results of the experiment can be found in [2].

Pohjolainen, S., Portier-Fozzani, F., Ragaigne, D.:
Comparison of 87 GHz solar polar structures with EUV and soft X-ray emission.
Astron. Astrophys. Suppl. Ser., Vol. 143, pp. 227-263, 2000.
Abstract: Polar radio brightenings at 87 GHz (3.5 mm) are compared for the first time with features seen in EUV and soft X-rays. The data consist of nearly simultaneous full disk images and maps from Metsähovi Radio Observatory, SOHO/EIT, and Yohkoh/SXT on 9 selected days near the solar minimum (1996-1997).

The observed radio brightenings corresponded to various features seen in EUV, such as diffuse or localized intensity enhancements (e.g., bright points and bases of polar plumes), and intensity depressions of varying sizes (e.g. coronal holes). Some of these features were also visible in soft X-rays. The visibility of radio bright coronal holes seemed to depend on how much the polar area was exposed, due to the variation of the B₀-angle.

The observed radio depressions near the solar poles were very well correlated with coronal holes and other EUV and/or soft X-ray intensity drops. More than half of the coronal holes, or coronal hole-like intensity drops in EUV and soft X-rays, had radio brightenings inside them. Therefore coronal holes do not have uniform radio brightness at 87 GHz.

Many of the bright points seen at lower latitudes in the EIT and SXT images had no, or just faint, counterparts in the millimeter radio maps. It appears that for an EUV bright point to show up at 87 GHz it has to be bright and/or spatially large also in soft X-rays.

Bloom, S.D., Hallum, J., Teräsranta, H., Tornikoski, M.:
Radio and millimeter spectral properties of newly identified high-energy gamma-ray sources.
The Astrophysical Journal, Vol. 529, pp. 675-681, 2000.
Abstract: We have conducted a variability study of several radio/millimeter sources that are possible counterparts of high-energy gamma-ray sources detected by EGRET. Some sources were possibly variable during this period. The radio source with the highest spectral and temporal coverage, PMN J0850-1213, behaves in a manner consistent with the shocked-jet models for extragalactic radio sources proposed in the literature. In addition, GB 105536.5 + 564424 is an X-ray-selected BL Lac object, and if the identification with the EGRET source is correct, it would be the most distant such object detected at energies > 100 MeV (z = 0.41). A future detection in the TeV range, as well, could provide an important constraint on absorption of very high energy gamma rays by the intergalactic infrared photon field. We also discuss the possibility that this object is a gravitationally microlensed active galactic nucleus, with the foreground lensing object at z = 0.144.

Grebinskij, A., Bogod, V., Gelfreikh, G.B., Urpo, S., Pohjolainen, S., Shibasaki, K.:
Microwave tomography of the solar magnetic fields.
Astronomy and Astrophysics Supplement Series, Vol. 144, pp. 169-180, 2000.
Abstract: We present a new technique for the measurement of magnetic fields in the solar chromosphere - corona through observations of its free-free microwave emission in intensity and polarization. We derive the decoupled radiation transfer equations for Stoke's parameters of I and V for circular polarized emission in plane-layer inhomogeneous atmospheres and present a model solutions of inversion problem. We discuss the discrimination between contributions from the corona and the chromosphere to the observed brightness spectra from the quiet Sun and plage regions and propose a practical method of magnetic field estimates, which was used both with single frequency (the Nobeyama Radioheliograph at 17 GHz) and multifrequency (RATAN at 1 - 16 GHz) observations and discuss the preliminary results. The proposed techniques may be useful as microwave magnetography at the corona base and for checks and improvements in the current problem of extrapolating magnetic fields from photosphere to corona.

Tuovinen, J., Kangaslahti, P., Haapanen, P., Hughes, N., Jukkala, P., Karttaavi, T., Koistinen, O., Lahdes, M., Salminen, H., Tanskanen, J., Urpo, S.:
Development of 70 GHz receivers for Planck LFI.
Astrophysical Letters and Communications, Vol. 37, pp. 181-187, 2000.
Abstract: Development of the Planck LFI 70 GHz cryogenic receiver is described. Most important components of this continuous correlation receiver, i.e. low noise amplifiers (LNA) will be based on the InP MMIC technology using co-planar transmission lines. First steps to obtain these LNAs and other MMICs are described. For the fabrication of the circuits either Daimler-Benz or TRW InP processing will be used. Important part of developing the front-and back-end modules will be good testing facilities for the needed circuits and devices. A unique on-wafer noise parameter testing facility at V-band is shown as well as the present status of cryogenic on-wafer testing set-up is presented.

Petry, D., Böttcher, M., Connaughton, V., Lähteenmäki, A., Pursimo, T., Raiteri, C.M., Schröder, F., Sillanpää, A., Sobrito, G., Takalo, L., Teräsranta, H., Tosti, G., Villata, M.:
Multiwavelength observations of Markarian 501 during the 1997 high state.
The Astrophysical Journal, Vol. 536, pp. 742-755, 2000.
Abstract: During the observation period 1997, the nearby blazar Mrk 501 showed extremely strong emission and high variability. We examine multiwavelength aspects of this event using radio, optical, soft and hard X-ray, and TeV data. We concentrate on the medium-timescale variability of the broadband spectra, averaged over weekly intervals. We confirm the previously found correlation between soft and hard X-ray emission and the emission at TeV energies, while the source shows only minor variability at radio and optical wavelengths. The nonlinear correlation between hard X-ray and TeV fluxes is consistent for the highest-energy electrons in the jet, and flux variations are caused by variations of the electron density and/or the spectra index of the electron injection spectrum. The time-averaged spectra are fitted with a synchrotron self-Compton (SSC) dominated leptonic jet model, using the full Klein-Nishina cross section and following the self-consistent evolution of relativistic particles along the jet, accounting for gamma gamma absorption and pair production within the source as well as due to the intergalactic infrared background radiation. The contribution from external inverse-Compton scattering is tightly constrained by the low-maximum EGRET flux and found to be negligible at TeV energies. We find that high levels of the X-ray and TeV fluxes can be explained by a hardening of the energy spectra of electrons injected at the base of the jet, in remarkable contrast to the trend for gamma-ray flares of the flat-spectrum radio quasar PKS 0528+134.

Pohjolainen, S.: On the origin of polar radio brightenings at short millimeter wavelengths.
Astronomy and Astrophysics, Vol. 361, pp. 349-358, 2000.
Abstract: Polar regions of the Sun are areas where coronal holes are most profound and where the heating and acceleration of solar wind plasma takes place. The observed and yet unexplained radio emission from these regions may be related to the origin of the solar wind flow. The recent analysis of radio brightenings near the poles at 87 GHs (3.5 mm) suggested structural counterparts like polar plumes. EUV and/or soft X-ray bright points, and diffuse EUV brightenings especially near the borders of coronal holes. Coronal holes themselves were mainly seen as radio depressed, with local radio brightenings inside them.

The radio brightness temperatures for these types of features are now calculated by using the average temperature and density values from EUV and soft X-ray observations, assuming isothermal and optically thin plasma. The calculated values are in agreement with the observed ones. The calculations show some bright points and plume bases to be observable in mm-waves (calculated brightness temperature enhancements 10-390 K, observed 30-150 K), but that the observability depends strongly on density and loop geometry (line of sight source length) of individual sources. Coronal holes in general should be seen as radio depressions at 87 GHz (calculated brightness temperature drops 30-40 K, observed drops 22-130 K) also a slight, 2.0 % maximum, smooth limb brightening is now found to affect the radio observations inside 0.6-0.92 R_O. This limb brightening is much less than reported in an earlier study using a similar telescope and same wavelength, which suggests a slightly different chromospheric model. The wide limb brightening does explain why some less intense EUV and soft X-ray features become observable in radio, as they get superposed on the smooth brightening.

Comparison to previous results obtained at several radio frequencies suggest that some of the high-latitude (<70 degrees) radio brightenings at 87 GHz could be formed in the same atmospheric layer as the diffuse radio emission sources in the polar-cap regions and the diffuse radio emission sources inside equatorial coronal holes - as they all show correlation to EUV emission sources, especially in the He II 304 Å (80 000 K) line. However, the unexplained 87 GHz radio brightenings inside high-latitude coronal holes, the radio bright patches observed in polar-cap regions, and the bright compact sources seen inside equatorial coronal holes all seem to share the fact that they are not associated with any features seen in EUV. The best candidates for the formation of these radio sources are magnetic flux elements and density/temperature enhancements below the 80 000 K layer.

Pursimo, T., Takalo, L. O., Sillanpää, A., Kidger, M., Lehto, H., Heidt, J., Charles, P. A., Aller, H., Aller, M., Benitez, E., Bock, H., Boltwood, P., Borgeest, U., DE Diego. J. A., De Francesco, G., Dietrich, M., Dultzin-Hacyan, D., Efimov Y., Fiorucci, M., Gonzalez-Perez, N., Hanski, M., Heinämäki, P., Honeycut, R. K., Hughes, P., Karlamaa, K., Katajainen, S., Knee, L.B.G., Kuemmel, M., Kurtanidze, O., Kühl, D., Lainela, M., Lanteri, L., Lindr, J.V., Lähteenmäki, A., Maesano, M., Mahoney, T., Marchenko, S., Marscher, A., Massaro, E., Montagni, F., Nesci, R., Nikolashvili, M., Nilsson, K., Nurmi, P., Pian, E., Pietilä, H., Poyner, G., Raiteri, C.M., Rekola, R., Richter, G.M., Riehokainen, A., Robertson, J.W., Rodriquez-Espinoza, J-M., Sadun, A., Shakhovskoy, N., Schramm, K.J., Schramm, T., Sobrito, G., Teerikorpi, P., Teräsranta, H., Tornikoski, M., Tosti, G., Turner, G.W., Valtaoja, E., Valtonen, M., Villata, M., Wagner, S.J., Webb, J., Weneit, W., Wiren, S.:
Intensive monitoring of OJ 287.
Astronomy and Astrophysics Supplement Series, Vol. 146, pp. 141-155, 2000.
Abstract: We present intensive optical, infrared, and radio monitoring observations of the BL Lac object OJ 287, taken between the years 1993-1998. Two large optical outbursts were detected at the predicted times in November 1994 and December 1995. The detection of these outbursts supports the binary black hole model for OJ 287. Optical and radio polarisation observations show large variability in the degree of polarisation and position angle, very similar to those observed during the 1983/84 outburst in OJ 287. The polarisation position angles show very similar behaviour during these observations, indicating that, at least, the magnetic field orientations in radio and optical bands are related in OJ 287. Optical and infrared light curves show continuous variability in time scales ranging from tens of minutes to years. In the radio bands we have observed some of the lowest ever measured flux levels. During the first optical outburst in November 1994 the observed radio flux was very low, but during the second optical outburst radio bands also showed high flux levels. This is a puzzling observation, which can hopefully be used for discriminating between different outburst models. On top of the large outbursts OJ 287 has displayed flaring activity in time scales from days to weeks and shorter time scale flickering.

Katajainen, S., Takalo, L.O., Sillanpää, A., Nilsson, K., Pursimo, T., Hanski, M., Heinämäki, P., Kotoneva, E., Lainela, M., Nurmi, P., Pietilä, H., Rekola, R., Riehokainen, A., Teerikorpi, P., Valtaoja, E., Lähteenmäki, A.:
Tuorla quasar monitoring. I. Observations of 1995 - 1997.
Astronomy and Astrophysics Suppl. Series, Vol. 143, pp.357-368, 2000.
Abstract: We present results of optical monitoring of quasars and blazars obtained at Tuorla Observatory between September 1995 and May 1997. The aim of our monitoring is to provide well sampled optical light curves for quasar and blazar studies. During the observing period the V-band brightness of S2 0109-224, 3C 66A, and ON 231 (W Comae) reached some of the brightest values ever measured for these objects. A strong outburst was observed in Mrk 421 and the large outburst, which was predicted earlier, in OJ 287 was confirmed. CTA 102 had over one magnitude outburst which happened in a timescale of a few days. For OI 090.4 we measured one of the faintest V-band brightness values ever.

Raiteri, C.M., Villata, M., Tosti, G., Fiorucci, M., Ghisellini, G., Takalo, L.O., Sillanpää, A., Valtaoja, E., Teräsranta, H., Tornikoski, M., Aller, M.F., Aller, H.D., De Francesco, G., Heinämäki, P., Katajainen, S., Lanteri, L., Nilsson, K., Pursimo, T., Rizzi, N., Sobrito, G.:
Optical and radio behaviour of the blazar S4 0954+65.
Astronomy and Astrophysics, Vol. 352, pp. 19-31, 1999.
Abstract: We present the results of an intensive optical and radio monitoring of the gamma-loud blazar S4 0954-65 from November 1994 to May 1998. The optical observations were done at the Torino, Perugia, and Tuorla Astronomical Observatories; in this period, including two pointings by the Energetic Gamma Ray Experiment Telescope (EGRET), the source was very active and reached its historical maximum. Intranight variability was checked during several nights, giving a positive answer. Colour-index variations were also detected, but no definite trend with brightness can be recognized. The radio light curves at 22 and 37 GHz from the Metsähovi Radio Observatory and those at 4.8 and 14.5 GHz from the University of Michigan Radio Astronomy Observatory (UMRAO) are not well sampled; however, two interesting fast-variability events are present, from which brightness temperatures exceeding the Compton limit by several orders of magnitude can be calculated. A comparison of the optical data with the radio ones does not lead to meaningful results because of the poor radio sampling. Finally, we analyse the spectral energy distributions (SEDs) from the radio to the optical band using contemporaneous radio and optical data taken during two different optical states, with a low radio flux corresponding to the high optical state and vice versa. We fist fit these SEDs by means of a helical-jet model, which suggests that the observed large, long-term variations can be due to changes of the jet orientation with respect to the line of sight. Then we fit the same SEDs with a homogeneous model, which can account for the high-energy part of the SED, stressing that external soft photons in addition to the local ones are required to explain the gamma-ray data.

Lähteenmäki, A., Valtaoja, E., Wiik, K.:
Total flux density variations in extragalactic radio sources. II. Determining the limiting brightness temperature for synchrotron sources.
Astrophysical Journal, Vol. 511, No 1, pp. 112-117, 1999.
Abstract: The maximum intrinsic brightness temperature T_b,lim for powerful synchrotron-emitting radio sources is usually assumed to be = 10¹² K, limited by the inverse Compton catastrophe. A lower value of = 5 x 10¹⁰ K based on the equipartition brightness temperature, has been suggested by Readhead on this basis of T_b,obs distributions derived from VLBI observations. We present two new methods for estimating T_b,lim in extragalaxtic radio source by using total flux density variations. A reasonable estimate of the value T_b,lim for a source can be obtained by comparing the Doppler boosting factors derived from total flux density variations at 22 and 37 GHz with traditional estimates based on the radio and synchrotron self-Compton (SSC) X-ray fluxes. Another independent estimate of T_b,lim is obtained by comparing the brightness temperatures derived from variability data with the values calculated from VLBI observations. Using several data sets, we find that both methods yield a value of < 10¹¹ K in accordance with the equipartition brightness temperature limit proposed by Readhead.

Brajsa, R., Ruzdjak, V., Vrsnak, B., Wöhl, H., Pohjolainen, S., Urpo, S.:
An estimate of microwave low brightness temperature regions' heights obtained measuring their rotation velocity.
Solar Physics, Vol. 184, pp. 281-296, 1999.
BR> Abstract: Daily full-disk solar maps obtained at 37 GHz in the years 1979, 1980, 1981, 1982, 1987, 1988, 1989, 1990, and 1991 are analysed and compared with full-disk solar maps in H_alpha. A search for a difference in the measured angular rotation velocity for two classes of microwave low-brightness- temperature regions (LTRs), associated and not associated with H_alpha filaments, is performed. Procedures with and without statistical weights, assigned to angular rotation velocities according to the tracing time, are applied and the statistical significance of the results is discussed. A higher angular rotation velocity is measured for LTRs associated with H_alpha filaments than for the not-associated ones. This angular velocity difference is interpreted as a consequence of a height difference between these two types of LTR tracers. Changes of the solar differential rotation velocity during the activity cycle measured using LTRs as tracers are explained by the measured cycle-dependence of the association rate between LTRs and H_alpha filaments. Similarly, the north-south asymmetry in the solar rotation velocity measured tracing LTRs is explained by the measured north-south asymmetry in the association rate between LTRs and H_alpha filaments. The rotation velocity of LTRs and H_alpha filaments is on the average more rigid in comparison with sunspots.

Falcke, H., Bower, G.C., Lobanov, A.R., Krichbaum, T.P., Patnaik, A.R., Aller, M.F., Aller, H.D., Teräsranta, H., Wright, M.C.H., Sandell, G.:
A major radio outburst in III Zw 2 with an extremely inverted, millimeter-peaked spectrum.
Astrophysical Journal, Vol. 514. pp. L17-L20, 1999.
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Abstract: III Zw is a spiral galaxy with an optical spectrum and faint extended radio structure typical of a Seyfert galaxy, but also with an extremely variable, blazar-like radio core. We have now discovered a new radio flare in which the source has brightened more than 20-fold within less than 2 yr. A broadband radio spectrum between 1.4 and 666 GHz shows a textbook-like synchrotron spectrum peaking at 43 GHz, with a self-absorbed synchrotron spectral index + 2.5 at frequencies below 43 GHz and an optically thin spectral index - 0.75 at frequencies above 43 GHz. The outburst spectrum can be well fitted by two homogenous, spherical components with equipartition sizes of 0.1 and 0.2 pc at 43 and 15 GHz and with magnetic fields of 0.4 and 1 G. VLBA observations at 43 GHz confirm this double structure and these sizes. Timescale arguments suggest that the emitting regions are shocks which are continuously accelerating particles. This could be explained by a frustrated jet scenario with very compact hot spots. Similar millimeter-peaked spectrum sources could have escaped our attention because of their low flux density at typical survey frequencies and their strong variability.

Türler, M., Paltani, S., Courvoisier, T.J-L., Aller, M.F., Aller, H.D., Blecha, A., Puchet, P., Lainela, M., McHardy, I.M., Robson, E.I., Stevens, J.A., Teräsranta, H., Tornikoski, M., Ulrich, M-H., Wamsteker, W.:
30 years of multi-wavelength observations of 3C 273.
Astronomy and Astrophysics Supplement series, Vol. 134, pp. 89-101, 1999.
Abstract: We present a wide multi-wavelength database of most observations of the quasar 3C 273 obtained during the last 30 years. This database is the most complete set of observations available for an active galactic nucleus (AGN). It contains nearly 20 000 observations grouped together into 70 light curves covering 16 orders of magnitude in frequency from the radio to the gamma-ray domain.

The database is constituted of many previously unpublished observations and most publicly available data gathered in the literature and on the World Wide Web (WWW). It is complete to the best of our knowledge, except in the optical (UBV) domain where we chose not to add all observations from the literature. In addition the photometric data, we present the spectra of 3C 273 obtained by the International Ultraviolet (IUE) satellite. In the X-ray domain, we used the spectral fit parameters from the literature to construct the light curves.

Apart from describing the data, we show the most representative light curves and the average spectrum of 3C 273. the database is available on the WWW in a homogeneous and clear from and we wish to update it regularly by adding new observations.

Valtaoja, E., Lähteenmäki, A., Teräsranta, H., Lainela, M.:
Total flux density variations in extragalactic radio sources. I. Decomposition of variations into exponential flares. Astrophysical Journal Supplement Series, Vol. 120, pp. 95-99, 1999.
Abstract: We show that 22 and 37 GHz total flux density variations in compact extragalactic radio sources can to a good accuracy be modeled by superposition of a small number of flare components. Both the rise and the decay of these flares are exponential, with a characteristic decay timescale 1.3 times longer than the rise timescale. The properties of the individual model flares derived from these flux decompositions are in agreement with data obtained from VLBI observations of the corresponding new shock components. The total flux density decompositions can be used to search correlations between radio and other regimes, to calibrate and to interpret VLBI observations, and to derive physical parameters of the amount of Doppler boosting in each source and, using additional VLBI data, to derive the intrinsic brightness temperatures, the Lorenz factors and the viewing angles of the sources.

Watson, D., Hanlon, L., McBreen, B., Smith, N., Foley, A.R., Metcalfe, L., Beckmann, V., Sánchez, S.F., Teräsranta, H.:
Simultaneous multifrequency observations of the BL Lac MS 0205.7+3509.
Astronomy and Astrophysics, Vol. 345, pp. 414-418, 1999.
Abstract: Radio and optical observations of the possible microlensed BL Lac source MS0205.7+3509 were obtained simultaneously with ASCA x-ray measurements in February 1997. A single power law model, with a photon index f 2.61, is an adequate fit to the ASCA data, once hydrogenic absorption in excess of the Galactic value is permitted, confirming a previous ROSAT measurement. On the basis of our simultaneous data we have determined MS 0205.7+3509 to be a typical x-ray select BL-Lac with alpha_xox = -0.82. There is no indication of an inverse Compton (IC) component in the ASCA spectrum up to 10 keV. No evidence for variability on hour-long timescales is present in either the x-ray or the optical data. We discuss these results in the context of a gravitational microlensing scenario for MS 0205.7+3509.

Bloom, S.D., Marscher, A.P., Moore, E.M., Gear, W., Teräsranta, H., Valtaoja, E., Aller, H.D., Aller, M.F.;
Multiwaveband observations of quasars with flat radio spectra and strong millimeter wave emission.
Astrophysical Journal Supplement Series, Vol. 122, pp. 1-27, 1999.
Abstract: We present multiwaveband observations of a well-selected sample of 28 quasars and two radio galaxies with flat radio spectra and strong millimeter-wave emission (referred to here as FSRQs). The data are analyzed to determine the radio to infrared and X-ray to gamma-ray properties of FSRQs and the relationships between them. Specifically, the synchrotron self-Compton (SSC) process is examined as a likely common radiation mechanism. For most sources, the broadband spectra are still incomplete, especially in the far-infrared and ultraviolet range. Therefore, precise analysis, such as model fitting of spectra, is not usually possible. To compensate partially for this, we have taken a statistical approach and examine the relationship between high- and low- energy emission by using the data set for the entire sample.

Pietilä, H., Takalo, L.O., Tosti, G., Benítez, E., Chiattelli, B., Corradi, R.L.M., Cox, G., De Diego, J.A., De Francesco, G., Dultzin-Hacyan, D., Heinämäki, P., Katajainen, S., Keinänen, P., Korhonen, H., Kotilainen, J., Lainela, M., Licandro, J., Luciani, M., Nilsson, K., Pursimo, T., Raiteri, C.M., Rekola, R., Sillanpää, A., Sobrito, G., Teräsranta, H., Villata, M., Zurita, A.:
OJ 287 and the predicted fade of 1998;
Astronomy and Astrophysics, Vol. 345, pp. 760-768, 1999.
Abstract: There were predictions that blazar OJ287 should have faded in late 1997 or early 1998. The observational background for these predictions is the sudden fade of OJ 287 in 1989. Back then, the radio flux decreased steadily for 4-5 months and then the brightness dropped also in the optical regions suddenly for 2-3 weeks to all time low values, e.g. V= 17.4 mag. The predictions are based on a binary black hole model, where the companion black hole and its accretion disk eclipse the emission areas of the primary black hole. We have made observations of OJ 287 during the time of the predicted fade. The results show that, in the optical, OJ 287 starts to fade almost linearly in December 1997 until mid-February 1998, when it suddenly shows a sharp rise and sharp fade and starts to get brighter again. The radio observations show no signs of variability, but the radio flux has been very low since the 1995 outburst. We also have earlier observations since Fall 1993 to Spring 1998, which show that the local minimum reached in February 1998 was the lowest since 1995. We have made observations with several telescopes in the optical (UBVRI) and radio (22 and 37 GHz) bands. We discuss the various events in the light curves and their implications on the proposed models, especially the binary black hole model by Lehto & Valtonen (1996), which was used to make the prediction of the time of the fade.

Klein, K.-L., Chupp, E.L., Trottet, G., Magun, A., Dunphy, P.P., Rieger, E., Urpo, S.:
Flare-associated energetic particles in the corona and at 1 AU
Astronomy and Astrophysics, Vol. 348, pp. 271-285, 1999.
Abstract: It is widely believed that the longest lasting and most energetic solar energetic particle events (SEPs) observed in interplanetary space result from acceleration by the bow shocks of coronal mass ejections (CMEs). Using gamma-ray, X-ray and radio diagnostics of interacting particles and spaceborne and ground-based detection of > 20 MeV protons at 1 AU during two large events (1989 September 29 and October 19), we demonstrate that time-extended acceleration processes in the low and middle corona, far behind the CME, leave their imprints in the proton intensity time profiles in interplanetary space for one to several hours after the onset of the flare: (1) New increases of > 20 MeV proton fluxes at 1 AU can be traced back to episodes of coronal acceleration. (2) Increasing richness of relativistic protons observed at 1 AU in the course of the SEPs is associated with new coronal particle injection after the impulsive phase. (3) Particle injection sites enabling a rapid access to the well-connected magnetic field line, as required by the SEP time profile, exist in the middle corona even if the nominal H_alpha flare location is far away. These findings suggest that contrary to the prevalent view acceleration processes in the low and middle corona supply both interacting and at least part of the interplanetary particles. The association of the most proton-rich component of the SEPs with delayed low-frequency radio emission is consistent with ionization state studies of SEPs, in that both require acceleration in a tenuous plasma. We conclude that the complexity of the corona provides the ingredients for the acceleration of particles and their injection into a large range of heliocentric angles. The CME may play the role of a trigger or even contribute to the buildup of magnetic stresses in the corona, but its bow shock is not the main accelerator of the high-energy protons.

Alcaraz J., Alvisi, D., Alpat, B., Ambrosi, G., Anderhub, H., Ao, L., Arefiev, A., Azzarello, P., Babucci, E., Baldini, L., Basile, M., Barancourt, D., Barao, F., Barbier, G., Barreira, G., Battiston, R., Becker, R., Becker, U., Bellagamba, L., Béné, P., Berdugo, J., Berges, P., Bertucci, B., Biland, A., Bizzaglia, S., Blasko, S., Boella, G., Bourquin, M., Bruni, G., Buenerd, M., Burger, J.D., Burger, W.J., Cai, X.D., Cavalletti, R., Camps, C., Cannarsa, P., Capell, M., Casadei, D., Casaus, J., Castellini, G., Chang, Y.H., Chen, H.S., Chen, Z.G., Chernoplekov, N.A., Chiarini, A., Chiueh, T.H., Chuang, Y.L., Cindolo, F., Commichau, V., Contin, A., Cotta-Ramusino, A., Crespo, P., Christinziani, M., da Cunha, J.P., Dai, T.S., Deus, J.D., Ding, L.K., Dinu, N., Djambazov, L., D'Antone, I., Dong, Z.R., Emonet, P., Eppling, F.J., Eronen, T., Esposito, G., Extermann, P., Favier, J., Feng, C.C., Fiandrini, E., Finelli, F., Fisher, P.H., Flaminio, R., Fluegge, G., Fouque, N., Galaktionov, Yu., Gervasi, M., Giusti, P., Gu, W.Q., Guzik, T.G., Hangarter, K., Hasan , A., Hermel, V., Hofer, H., Huang, M.A., Hungerford, W., Ionica, M., Ionica, R., Isbert, J., Jongmanns, M., Karpinski, W., Kenney, G., Kenny, J., Kim, W., Klimentov, A., Krieger, J., Kossakowski, R., Koutsenko, V., Laborie, G., Laitinen, T., Lamanna, G., Laurenti, G., Lebedev, A., Lee, S.C., Levi, G., Leytchenko, P., Li, T.P., Liu, C.L., Liu, H.T., Lolli, M., Lopes, I., Lu, G., Lu, Y.S., Lübelsmeyer, K., Luckey, D., Lustermann, W., Maehlum, G., Mana, C., Margotti, A, Massera, F., Mayet, F., McNeill, R.R., Meillon, B., Menichelli, M., Mezzanotte, F., Mezzenga, R., Mihul, A., Molinari, G., Mourao, A., Mujunen, A., Palmonari, F., Pancaldi, G., Papi, A., Park, I.H., Pauluzzi, M., Pauss, F., Perrin, E., Pesci, A., Pevsner, A., Pilastrini, R., Pimenta, M., Plyaskin, V., Pojidaev, V., Postema, H., Prati, E., Produit, N., Rancoita, P.G., Rapin, D., Raupach, F., Recupero, S., Ren, D., Ren, Z., Ribordy, M., Richeux, J.P., Riihonen, E., Ritakari, J., Roeser, U., Roissin, C., Sagdeev, R., Santos, D., Sartorelli, G., Schultz von Drazig, A., Schwering, G., Shoutko, V., Shoumilov, E., Siedling, R., Son, D., Song, T., Steuer, M., Sun, G.S., Suter, H., Tang, X.W., Ting, Samuel, C.C., Ting, S.M., Tenbusch, F., Torromeo, G., Torsti, J., Trümper, J., Ulbricht, J., Urpo, S., Usoskin, I., Valtonen, E., Vandenhirtz, J., Velikhov, E., Verlaat, B., Vetlitsky, I., Vezzu, F., Vialle, J.P., Viertel, G., Vite, D., Von Gunten, H., Waldmeier Wicki, S., Wallraff., W., Wang, B.C., Wang, J.Z., Wang, Y.H., Wefel, J.P., Werner, E.A., Williams, C., Wu, S.X., Xia, P.C., Yan, J.L., Yan, L.G., Yang, C.C.,Yang, M., Yeh, P., Zhang, H.Y., Zhao, D.X., Zhu, G.Y., Zhu, W.Z., Zhuang, H.L., Zichichi, A.:
Search for Antihelium in Cosmic Rays.
Physics Letters B, http://hpl3tri1.cern.ch/AMS/Publications/ Vol. 461, pp. 387-396, 1999.
Abstract: The Alpha Magnetic Spectrometer (AMS) was flown on the space shuttle Discovery during flight ST-91 in a 51.7º orbit at altitudes between 320 and 390 km. A total of 2.86 x 10⁶ helium nuclei were observed in the rigidity range 1 to 140 GV. No antihelium nuclei were detected at any rigidity. An upper limit on the flux ratio of antihelium to helium of < 1.1 x 10^-6 is obtained.

Takalo, L.O., Pursimo, T., Sillanpää, A., Hanski, M., Heinämäki, P., Katajainen, S., Lainela, M., Nilsson, K., Nurmi, P., Pietilä, H., Rekola, R., Riehokainen, A., Valtaoja, E., Aller, M., Aller, H., Hughes, P., Cavallone, M., De Francesco, G., Lanteri, L., Raiteri, C.M., Sobrito, G., Villata, M., Efimov, Y, Shakhovskoy, N., Tosti, G., Fiorucci, M., Nucciarelli, G., Maesano, M., Massaro, E., Montagni, F., Nesci, R., D'Alessio, F., Honeycut, R.K., Robertson, J.W., Turner, G.W., Teräsranta, H., Tornikoski, M., Boltwood, P., Sadun, A., Poyner, G.:
Radio and optical monitoring of 3C 66A during an extended outburst. II. 1995-1997.
1999 BLAZAR Data Vol. 1, n. 6, 61 p., 1999.
Abstract: We present new monitoring observations of the BL Lac object 3C66A, taken between the years 1995-1997. During this period the object was always observed in an outburst phase, which started in 1993. Only towards the end of this observing period the brightness level started to decrease, suggesting that the outburst is probably over. Characteristic to the optical light curves are frequent large flares and small amplitude flickering. The radio data show less violent variations, with indications of a small amplitude outburst.

Lähteenmäki, A., Valtaoja, E.:
Total flux density variations in extragalactic radio sources. III. Doppler boosting factors, Lorenz factors and viewing angles for active galactic nuclei.
Astrophysical Journal, Vol. 521, pp. 493-501, 1999.
Abstract: We have calculated Doppler boosting factors D_var, for a sample of active galactic nuclei (AGNs) using total flux density variation monitoring data at 22 and 37 GHz. We argue that this method is more accurate than the other commonly used methods based on the synchrotron self-Compton X-ray flux or equipartition of energy. We compare our Doppler factors with other results and conclude that even if the average D_var for a class of sources is very similar to all others, the variability Doppler factors for individual objects are more accurate and reliable. An important application of precise Doppler factors is presented, namely, calculating the Lorenz factors, gamma, and the viewing angles , of relativistic outflows in AGNs. We find that high-polarization quasars have the greatest Doppler boosting, while low- polarization quasars and BL Lac objects are less boosted. The two groups of quasars show different characteristics because of different combinations of the Lorentz factor and viewing angle, rather than either a different gamma or alone.

Lähteenmäki, A., Valtaoja, E.:
Optical polarization and imaging of hot spots in radio galaxies.
Astronomical Journal, Vol. 117, pp. 1168-1174, 1999.
Abstract: We present subarcsecond optical imaging and polarization observations of five optical hot spot candidates in the classical double radio sources 3C 111, 3C 303, 3C 351, 3C 390.3, and PKS 2135-147. On the basis of positional coincidence, optical appearance, and polarization, all four 3C sources appear to have genuine optical counterparts to radio hot spots, whereas in PKS 2135-147 the hot spot candidate turns out to be an unrelated field galaxy. We also confirm the first ever optical double hot spot in the source 3C 351.

Alcaraz J., Alvisi, D., Alpat, B., Ambrosi, G., Anderhub, H., Ao, L., Arefiev, A., Azzarello, P., Babucci, E., Baldini, L., Basile, M., Barancourt, D., Barao, F., Barbier, G., Barreira, G., Battiston, R., Becker, R., Becker, U., Bellagamba, L., Béné, P., Berdugo, J., Berges, P., Bertucci, B., Biland, A., Bizzaglia, S., Blasko, S., Boella, G., Boschini, M., Bourquin, M., Bruni, G., Buenerd, M., Burger, J.D., Burger, W.J., Cai, X.D., Cavalletti, R., Camps, C., Cannarsa, P., Capell, M., Casadei, D., Casaus, J., Castellini, G., Chang, Y.H., Chen, H.S., Chen, Z.G., Chernoplekov, N.A., Chiarini, A., Chiueh, T.H., Chuang, Y.L., Cindolo, F., Commichau, V., Contin, A., Cotta-Ramusino, A., Crespo, P., Christinziani, M., da Cunha, J.P., Dai, T.S., Deus, J.D., Dinu, N., Djambazov, L., D'Antone, I., Dong, Z.R., Emonet, P., Engelberg, J., Eppling, F.J., Eronen, T., Esposito, G., Extermann, P., Favier, J., Feng, C.C., Fiandrini, E., Finelli, F., Fisher, P.H., Flaminio, R., Fluegge, G., Fouque, N., Galaktionov, Yu., Gervasi, M., Giusti, P., Grandi, D., Gu, W.Q., Hangarter, K., Hasan , A., Hermel, V., Hofer, H., Huang, M.A., Hungerford, W., Ionica, M., Ionica, R., Jongmanns, M., Karlamaa, K., Karpinski, W., Kenney, G., Kenny, J., Kim, W., Klimentov, A., Krieger, J., Kossakowski, R., Koutsenko, V., Laborie, G., Laitinen, T., Lamanna, G., Liu, H.T., Lolli, M., Lopes, I., Lu, G., Lu, Y.S., Lübelsmeyer, K., Luckey, D., Lustermann, W., Mana, C., Margotti, A, Massera, F., Mayet, F., McNeill, R.R., Meillon, B., Menichelli, M., Mezzanotte, F., Mezzenga, R., Mihul, A., Molinari, G., Mourao, A., Mujunen, A., Palmonari, F., Pancaldi, G., Papi, A., Park, I.H., Pauluzzi, M., Pauss, F., Perrin, E., Pesci, A., Pevsner, A., Pilastrini, R., Pimenta, M., Plyaskin, V., Pojidaev, V., Postema, H., Postolache, V., Prati, E., Produit, N., Rancoita, P.G., Rapin, D., Raupach, F., Recupero, S., Ren, D., Ren, Z., Ribordy, M., Richeux, J.P., Riihonen, E., Ritakari, J., Roeser, U., Roissin, C., Sagdeev, R., Santos, D., Sartorelli, G., Schultz von Drazig, A., Schwering, G., Seo, E.S., Shoutko, V., Shoumilov, E., Siedling, R., Son, D., Song, T., Steuer, M., Sun, G.S., Suter, H., Tang, X.W., Ting, Samuel, C.C., Ting, S.M., Tornikoski, M., Torromeo, G., Torsti, J., Trümper, J., Ulbricht, J., Urpo, S., Usoskin, I., Valtonen, E., Vandenhirtz, J.,Velcea, F., Velikhov, E., Verlaat, B., Vetlitsky, I., Vezzu, F., Vialle, J.P., Viertel, G., Vite, D., Von Gunten, H., Waldmeier Wicki, S., Wallraff., W., Wang, B.C., Wang, J.Z., Wang, Y.H., Wiik, K., Wefel, J.P., Werner, E.A., Williams, C., Wu, S.X., Xia, P.C., Yan, J.L., Yan, L.G., Yang, C.C., Yang, M., Ye, S.W., Yeh, P., Xu, Z.Z., Zhang, H.Y., Zhang, Z.P., Zhao, D.X., Zhu, G.Y., Zhu, W.Z., Zhuang, H.L., Zichichi, A.:
Protons in Near Earth Orbit.
Physics Letters B, http://hpl3tri1.cern.ch/AMS/Publications/ Vol. 472, pp 215-226, 1999.
Abstract: The proton spectrum in the kinetic energy range 0.1 to 200 GeV was measured by the Alpha Magnetic Spectrometer (AMS) during space shuttle flight STS-91 at an altitude of 380 km. Above the geomagnetic cutoff the observed spectrum is parameterized by a power law. Below the geomagnetic cutoff a substantial second spectrum was observed concentrated at equatorial latitudes with a flux ~ 70 m^-2sec^-1sr^-1. Most of these second spectrum protons follow a complicated trajectory and originate from a restricted geographic region.

Tornikoski, M., Tingay, S.J., Mücke, A., Chen, A., Connaughton, V., Jauncey, D.L., Johnston-Hollitt, M., Kemp, J., King, E.A., McGee, P., Rantakyrö, F., Rayner, D., Reimer, O., Tzioumis, A.K.:
Multiwavelength observations of PKS 2255-282.
Astronomical Journal, Vol. 118, pp. 1161-1168, 1999.
Abstract: During high radio frequency active galactic nucleus monitoring, we observed a major millimeter wave outburst from PKS 2255-282 in 1997 and initiated a campaign for multifrequency radio monitoring and VLBI imaging of the source. In 1998 January the EGRET instrument on board the Compton Gamma Ray Observatory detected a bright high-energy gamma-ray outburst from its direction. Thus we had the unique opportunity to monitor the source in detail at various radio frequencies already before the detection of the gamma-ray outburst. We also initiated multiwavelength follow-up observations. In this paper we present multiwavelength data for PKS 2255-282 before and after the gamma-ray outburst. Further, based on the observations, we estimate some physical parameters for this source and discuss the various emission mechanisms possibly involved during this outburst.

NESTEROV N S, LYUTY V M, VALTAOJA E: Radio and optical evolution of the Seyfert galaxy NGC 1275; Astronomy and Astrophysics, Vol 296, pp 628-632, 1995. Abstract: The results of extensive observations of the Seyfert galaxy NGC 1275 carried out at the radio frequencies 22 GHz, 37 GHz and 87 GHz, and in the optical V band are presented. Two types of variations in the continuum emission of the galaxy nucleus are found. Fast outbursts occur at radio frequencies 5-6 years after the corresponding optical events. These outbursts are identified with shocks forming in the radio jet. They also correspond to ejections of new VLBI components from the core. The second type of variation is caused by a slowly changing component having a time delay of ( 8 years between radio and optical domains. We propose that this variation results from a period of enhanced accretion rate in the nucleus, beginning in the 1950s and ending around 1980, and leading to the growth and subsequent decay of the radio emitting jet. Linear extrapolation of the expansion speeds of these two types of components indicates that the true galaxy nucleus is located at a distance of a few parsecs from the radio core (the beginning of the visible jet). This estimate would place the nucleus halfway between the 'radio core' and the recently discovered 'counterjet'.

MUKHERJEE R, ALLER H D, ALLER M F, BERTSCH D L, COLLMAR W, DIGEL S W, DINGUS B L, ESPOSITO J A, FICHTEL C E, HARTMAN R C, HUNTER S D, JOHNSON W N, KANBACH G, KNIFFEN D A, LIN Y C, MATTOX J R, MAYER-HASSELWANDER H A, MICHELSON P F, VON MONTIGNY C, NOLAN P L, RAMANAMURTHY P V, SCHNEID E, SREEKUMAR P, TERÄSRANTA H, THOMPSON D J, WAGNER S J: EGRET gamma-ray sources: GRO J0744+54 and GRO J0957+65 (=BL Lac Object 0954+658); Astrophysical Journal, Vol 445, pp 189-195, 1995. Abstract: EGRET detected an unidentified source, GRO J0744+54, at a significance of 6,5 (, during its observations from 1993 June 28 to July 12. The source was seen again in the following 2 week viewing period and was weakly evident in the earlier phase 1 of the EGRET observations. Considering the variability of its gamma-ray flux and its location at high Galactic latitude, GRO J0744+54 is likely to be a previously undetected blazar. Its most likely identification is with the radio source 87GB 073840.5+545138. A second source GROJ0957+65, was seen by EGRET during the same two viewing periods at a combined significance of 5.7 (. The most probable counterpart of GRO J0957+65 is the BL Lacertae object 0954+658. The spectra, time variability, and positions of the two sources are presented. Multiwavelength observations of 0954+658 are also presented.

GRANDI P, MARASCHI L, URRY C M, WEHRLE A E, ALLER M F, ALLER H D, BALONEK T J, JASON J, McHARDY I M, HARTMAN R C, PIAN, E, STEVENS J A, SADUN A C, TERÄSRANTA H, TREVES A: Long term variability of 3C279; Advances in Space Research, Vol 15, No 5, pp 23-26, 1995. Abstract: Radio, mm, optical, UV and X-ray light curves of 3C 279 as well as the (-ray light curve available since 1991 June are considered. Strong flux correlations are found between the X-ray and the radio-optical region. Variations at 100 MeV are well correlated to the optical and X-ray bands. The variability amplitude, as measured by an average logarithmic dispersion of the available measurements is small in the radio and increases systematically with increasing frequency up to the (-ray band, with the possible exception of the X-ray amplitude.

VALTAOJA E, TERÄSRANTA H: Gamma radiation from radio schocks in AGN jets; Astronomy and Astrophysics, Vol 297, pp L13-L16, 1995. Abstract: We compare the Phase 1 gamma-ray detections and nondetections of active galactic nuclei by the EGRET instrument of Compton Gamma Ray Observatory with Metsähovi 22 GHz and 37 GHz radio flux curves. We find a good correlation between the type of the source, the radio state of the source, and the gamma-ray emission. With few exceptions, gamma-rays are detected when, and only when, a quasar with high optical polarization is in the initial phases of a high radio frequency outburst. Other types of sources - low polarization quasars, BL Lac objects, radio galaxies - are rarely detected in gamma-rays, even when in a similar state of radio activity. Our results limit viable gamma-ray production mechanisms to those involving strongly beamed gamma-rays from radio-emitting shocks in jets oriented close to our line of sight.

LAGERQVIST C-I, ERIKSON A, DEBEHOGNE H, FESTIN L, MAGNUSSON P, MOTTOLA S, OJA T, DeANGELIS G, BELSKAYA I N, DAHLGREN M, GONANO-BEURER M, LAGERROS J, LUMME K, POHJOLAINEN S: Physical studies of asteroids. XXIX. Photometry and analysis of 27 asteroids; Astronomy and Astrophysics Supplement Series, Vol 113, No 1, pp 115-129,1995. Abstract: The asteroid 153 Hilda was studied by photometric, spectroscopic and polarimetric observations during the apparition in 1992. The rotation period was determined to 5.11 hours with a lightcurve amplitude of 0.05 magnitudes. From our spectrum we find 153 Hilda to be of taxonomic type P. The polarization value of -0.23 at a phase angle of 3.2 degrees seems normal for a P-type asteroid. Long term integrations of the orbit shows that it is stable over time intervals of several million years.

STEVENS J.A., LITCHFIELD S J, ROBSON E I, GEAR W K, TERÄSRANTA H, TORNIKOSKI M, VALTAOJA E: The spectral evolution of high frequency radio outbursts in the blazar PKS 0420-014; Monthly Notices of the Royal Astronomical Society, Vol 275, pp 1146-1154, 1995. Abstract: Multifrequency monitoring data between 375 and 22 GHz are used to investigate the spectral evolution of radio outbursts in the blazar 0420-014. It is shown that, after subtraction of the underlying 'quiescent' emission, the flare spectrum can be described by a simple homogeneous self-absorbed synchrotron component. The evolution of this spectrum is found to be qualitatively consistent with the shock model of Marscher & Gear, although not totally so in detail. Some of the discrepancies can possibly be resolved if the proposed relativistic jet, which is initially oriented close to the line-of-sight, bends away. The optically thin spectrum of the flare emission, however, is found to be flatter than allowed by the model. Strong correlations are found between the 90-22 GHz twopoint spectral index and the logarithm of the 90-GHz flux. These trends are reconciled with the evolution of the synchrotron spectrum during the flares.

PIAN E, EDELSON R A, WAGNER S J, BREGMAN J, GEORGE I, TREVES A, WAMSTEKER W, BOCK H, CARINI M, COURVOISIER T, DONAHUE M, EFIMOV Y, FILIPPENKO A, FINK H, HEIDT J, LAWRENCE A, MARSCHI L, MILLER H R, PIKE G, QUIRRENBACH A, SHAKHOVSKOY N, SILLANPÄÄ A, SITKO M, SMITH P, TAKALO L, TERÄSRANTA H, VALTAOJA E, WARD M, WARWICK R: Simultaneous UV, optical and radio monitoring of the BL LAC object OJ 287 in March 1993; 30th COSPAR meeting, Hamburg, July 11-21, 1994, Advances in Space Research, Vol 16, No 3, pp (3)57-(3)60, 1995. Abstract: The BL Lacertae object OJ 287 was intensively monitored with the IUE satellite from 1993 March 15 to 20 in the 2000-3000 wavelength region. The very low emission state of the source hampered the detection during part of the 23 performed exposures. The light curve at 2650 constructed with the 11 best images exhibits a variable trend with a factor ( 2 enhancement of the flux in about 3 hours. Simultaneous ground based observations show an optical flux variability of smaller amplitude, but correlated with the UV light curve without any apparent lag. The radio light curve is nearly constant. The UV emission state is the weakest observed in 15 years for this flaring blazar, being a factor of ( 20 lower than the maximum recorded one.

LEPPÄNEN K J, ZENSUS J A, DIAMOND P J: Linear Polarization Imaging with Very Long Baseline Interferometry at High Frequencies; Astronomical Journal, Vol 110, No 5, pp 2479-2492, 1995. Abstract: We describe a new method to self-calibrate the instrumental polarization characteristics in polarimetric very long baseline interferometry (VLBI) observations. The method is especially useful at high frequencies where no suitable calibrator sources with known polarization properties are available. In a test experiment with the Very Long Baseline Array (VLBA), the feed polarization parameters (D-factors) were calibrated to within 0.2 % RMS using a compact continuum source. This made possible measuring the fractional polarization with a maximum accuracy of 0.15 %. Higher calibration accuracy could be obtained with H20-maser sources. We demonstrate that the electric vector orientation can be calibrated internally with the VLBA at 22 GHz. Therefore, VLBP observations without calibrator sources are possible at this frequency. We applied the method to VLBA observations of three active galactic nuclei (AGN) and imaged the linear polarization structure of AGN for the first time at 22 GHz. In 3C 345 and 3C 279 the inferred magnetic field is predominantly perpendicular in the jet. In 3C 273 the magnetic field is approximately longitudinal within 2 milliarcsecond of the core; at larger distances the field is random. The core polarization is low in all three quasars (<3 %), whereas the jet components are up to 30 % polarized. The polarization properties of 3C 345 and 3C 279 are largely consistent with a general model based on strong plane-perpendicular shocks in the jet plasma; the properties of 3C 273 cannot be easily explained by simple shock models.

TOTH L V, HAIKALA L, LILJESTRÖM T, MATTILA K: L1780: a cometary globule associated with Loop I; Astronomy and Astrophysics, Vol 295, pp 755-766, 1995. Abstract: 12CO, 13CO and C18O J = 1 ( 0 observations of the L1778/L 1780 high latitude (b = 36(.7) dark cloud have been carried out using the Gornergrat 3m and SEST 15m telescopes. The observations revealed a cometary cloud structure: a dense core asymmetrically surrounded by a diffuse outer layer. The mass of the cloud calculated from the CO observations is 21.6 M(. The compact 13CO core has a mass of 8.3M( and is found to be in virial equilibrium. The CO data have been compared to previous optical, H I, and IRS observations. We suggest that the structure and the morphology of L 1780 have been influenced by two large scale environmental effects: (1) the asymmetric interstellar UV radiation field and (2) a shock front, both caused by the high mass stars of the Sco - Cen OB association.

TORNIKOSKI M, VALTAOJA E, TERÄSRANTA H, KARLAMAA K, LAINELA M, NILSSON K, KOTILAINEN J, LAINE S, LÄHTEENMÄKI A, KNEE L B G, BOTTI L C L: SEST Observations of extragalactic radio sources at 3 mm and 1.3 mm; Astronomy and Astrophysics Supplement Series, Vol 116, pp 157-165, 1996. Abstract: Flux densities of 155 extragalactic radio sources observed with the SEST telescope at 3 mm and 1.3 mm are presented. The observations were performed from October 1987 to June 1994. In addition to the flux density tables we have plotted the flux density curves for some of the most frequently observed sources.

GRANDI P, URRY C M, MARASCHI L, WEHRLE A E, MADEJSKI G M, ALLER M F, ALLER H D, BAILYN C D, BALONEK T J, BOCK T H, GLASS I S, McHARDY I M, MULCHAYE J S, LITCHFIELD S J, REUTER H P, SADUN A C, SHERRY W, STEPPE H, STEVENS J A, TERÄSRANTA H, TORNIKOSKI, M, WAGNER S J: 3C 279 multiwavelength monitoring: II. Ground-based campaign; The Astrophysical Journal, Vol 459, pp. 73-81, 1996. Abstract: The optical violently variable quasar 3C 279 was monitored simultaneously from radio to g-ray frequencies in 1992 December - 1993 January. We report a detailed study of the ground-based resluts from radio to optical wavelengths. These data show that 3C 279 has a typical blazar spectrum, slightly rising at radio frequency and then progressively steeper above a first turnover frequency between 37 and 90 GHz. In the millimeter wavelength region, a simple power law is not an adquate description of the spectrum. We suggest that the millimeter "shoulder" corresponds to an additional emission component, self-absorbed between 150 and 375 GHz, possibly associated with the detachment of a new VLBI knot and with the start of radio flare. A flux increase of 20 % over 20 days was observed at 37 and 90 GHz, while conteporaneously the R-band flux doubled in about two weeks. The lack of strong variability in contemporaneous X-ray light curves (possible X-ray variations are less than 30 %) implies no direct (i.e., zero lag) correlations between the optical and X-ray fluxes. If X-rays are produced by inverse-Compton scattering of relativistic electrons on some seed photons, the above results exclude that the optical band are responsible for the scattering to X-ray energies. We suggest that the X-rays are instead produced through the inverse-Compton process by electrons of lower energy, which radiate via synchrotron in the radio millimeter wave bands and which scatter either on the synchrotron photons themselves or on external photons.

BRAJSA R, POHJOLAINEN S, RUZDJAK V, SAKURAI T, URPO S, VRSNAK B, WÖHL H: Helium 10830 measurements of the Sun; Solar Physics, Vol 163, pp 79-91, 1996. Abstract: Measurements of theSun in the near-infrared He I 10830 absorption line were performed using the echelle spectrograph with a dispersion of 6.71 m per pixel at the Vacuum Tower Telescope (German Solar Telescopes, Teide Observatory, Izana, Tenerife, Spain) on May 26, 1993. These measurements were compared with full-disc soft X-ray images of the Sun (Japanese solar satellite Yohkoh), full-disc solar images in Ha (Big Bear Solar Observatory), full-disc solar images in the He I 10830 line (National Solar Observatory, Kitt Peak) and with full-disc microwave solar maps at 37 GHz (MetsÄhovi Radio Research Station). In the He 10830 line the Sun displays a limbdarkening similar to that in the visible part of the spectrum. Active regions and Ha filaments show a strong absorption in the He 10830 line, whereas the absorption is weak in coronal holes.

POHJOLAINEN S, URPO S, HERRMANN R: A multi-wavelength study of a series of solar flares on June 11, 1991; 30th COSPAR Scientific Assembly, Hamburg, Germany, July 11-21, 1994, Advances in Space Research, Vol 17, No 4/5, pp 139-142, 1996. Abstract: On June 11, 1991, at 8:00-9:30 UT, several flares were observed in the active region 6659 (N38W24). We have studied the time development, fine-structures, spectral features, polarization , and correlation between different wavelengths of each of these events. The data used in the analysis are Metsähovi and Bern microwave data, GOES7 soft X-ray data, and other wavelength information from the Solar Geophysical Data.

ESKELINEN P, ENGELBERG J: Tests on a 3 GHz ground plane yagi; IEEE Aerospace and Electronic Systems Magazine, Vol 11, No 2, pp 37-40, 1996. Abstract: Classical dimensioning of a ground plane yagi antenna for 3 GHz leads to a gain which is 2-3 dB less than predicted, but this can be overcome to some extent by additional directors. The impedance matching strongly depends on the size of the reflector, which should be by a factor of 1.2 longer than given by classical theory. The shape and size of the ground plane itself can be varied considerably with little or no effect on either the radiation pattern or the impedance characteristics but, on the other hand, inaccurate mutual positioning of the individual elements has a drastic influence. Material conductivity is not of prime concern.

HARTMAN RC, WEBB J R, MARSCHER A P, TRAVIS J P, DERMER C D, ALLER M F, ALLER H D, BALONEK T J, BENNETT K, BLOOM S D, FUJIMOTO R, HERMSEN W, HUGHES P, KII T, KURFESS J D, MAKINO F, MATTOX J R, VON MONTIGNY C, OHASHI T, ROBSON I, RYAN J, SADUN A, SCHÖNFELDER V, SMITH A G, TERÄSRANTA H, TORNIKOSKI M, TURNER M J L: Simultaneous multiwavelength spectrum and variability of 3C 279 from 109 to 1024 Hz; Astrophysical Journal, Vol 461, pp 698-712, 1996. Abstract: Data from a number of monitoring programs have been combined with data from the Compton Gamma Ray Observatory and the Ginga X-ray satellite to construct a spectrum covering nearly 15 decades in frequency during or near the time of the 3 C 279 g-ray flare observed by EGRET in 1991 June. A much less complete spectrum is presented for 1991 October. Light curves from early 1991 to mid-1992 are presented for radio, millimeter, submillimeter, infrared, optical and g-rays. Although the temporal coverage is incomplete, the only evidence for correlation in variability between the g-rays and lower frequencies is a flare in the optical R-band that peaks within ~ 1 day of the maximum in the g-ray light curve. The variability shows higher relative amplitude in g-rays than in the R band. We present spectral fits to the overall multi-wave band spectrum averaged over the 1991 June flare corresponding to two models: (i) synchrotron self-Compton (SSC) emission from a relativistic jet and (ii) inverse Compton scattering of seed photons originating external to the jet (ECS) by the synchrotron-emitting relativistic electrons in the jet. Either model can fit the observed spectra satisfactorily. The higher amplitude of the g-ray variations is as predicted by the SSC model and can be accomodated within the ECS model of the flare is caused by a temporary change in the bulk Lorentz factor of the g-ray emitting plasma.

POHJOLAINEN S, VALTAOJA E, URPO S: Solar microwave burst classification and correlation with soft X-rays; Astronomy and Astrophysics, Vol 306, pp. 973-980, 1996. Abstract: A large sample of microwave bursts observed at the Metsähovi Radio Research Station during 1989-1992 was analysed and the corresponding active regions were classified. The burst-producing active regions could be divided into three types according to their burst features. The bursts recorded at 37 GHz (8 mm wavelength) were also compared with the GOES soft X-ray data. The gradual rise and fall type burst fluxes showed almost linear correlation with soft X-ray fluxes, but no common denominator could be found for those radio bursts that lacked a counterpart at soft X-rays. Most of the impulsive microwave bursts were found to start and peak just before the soft X-ray maximum, while many of the gradual bursts started soon after the X-ray onset and peaked after the X-ray maximum. The X-ray flux rise before microwave onset was found to correlate with the maximum X-ray flux, in both impulsive and gradual burst events, the correlation coefficient depending on the soft X-ray flux.

ÖSTENSEN R, REFSDAL S, STABELL R, TEUBER J, EMANUELSEN P I, FESTIN L, FLORENTIN-NIELSEN R, GAHM G, GULLBRING E, GRUNDAHL F, HJORTH J, JABLONSKI M, JAUNSEN A O, KAAS A A, KARTTUNEN H, KOTILAINEN J, LAURIKAINEN E, LINDGREN H, MÄHÖNEN P, NILSSON K, OLOFSSON G, OLSEN Ö, PETTERSEN B R, PIIROLA V, SÖRENSEN A N, TAKALO L, THOMSEN B, VALTAOJA E, VESTERGAAR M, av VIANBORG T: Monitoring of the Einstein cross with the Nordic Optical Telescope; Astronomy and Astrophysics, Vol 309, pp 59-64, 1996. Abstract: We report results from five years of monitoring of the Einstein Cross (QSO 2237+00305) with the Nordic Optical Telescope. The photometry, mainly in the R and I bands, has been performed by a PSF fitting and 'cleaning' procedure, in which the four image components as well as the host galaxy and its nucleus are iteratively removed. The resulting lightcurves exhibit several microlensing features; one event may have a timescale as short as 14 days. Variations on timescales of several years are found in all four images. This becomes even mores convincingwhen our data are combined with data published for 1986-89. No clear high amplification event was observed during the period. A brightening of all four components during 1994 is interpreted as intrisic variation.

MUKHERJEE R, DINGUS B L, GEAR W K, HARTMAN R C, HUNTER S D, MARSCHER A P, MOORE E M, ROBSON E I, SREEKUMAR P, STEVENS J A, TERÄSRANTA H, TORNIKOSKI M, WAGNER S J, ZHANG Y F: EGRET observations of the 1993 March gamma-ray flare from PKS 0528+134; Astrophysical Journal, Vol 470, pp 831-838, 1996. Abstract: EGRET observation of PKS 0528+134 during the 1993 March flare in gamma-rays is presented here. During the flare gamma-rays were detected at a level approximately three times greater than the observed intensity in earlier observations. Spectra of the source during the flare, as well as during the nonflaring state are presented. The flux history of PKS 0528+134 as observed from the start of the Compton Gamma Ray Observatory (CGRO) mission up to the end of Phase 3 (1993 October) is given. Multiwavelength observations of PKS 0528+134 during the flare are also presented. A detailed relativistic SSC jet model agrees well with the 1993 March Multiwavelength spectrum; the data, however, are insufficient to discriminate between this and other emission models.

POHJOLAINEN S, VALTAOJA E, URPO S: Solar microwave burst emission relation to X-ray radiation; Astronomy and Astrophysics, Vol 314, pp 947-956, 1996. Abstract: We have calculated the thermal bremsstrahlung component for 87 microwave burst observed at a near-millimeter wavelength (37 GHz), using a well-known procedure for computing the plasma temperature and emission measure from the GOES soft X-ray data. The calculated values showed good correlation with the observed fluxes in gradual rise and fall-type bursts. In the majority of impulsive type bursts a bremsstrahlung component was found to be present, often as a post-burst increase. Some bursts without a thermal component were found and they could be connected with higher energy electrons producing hard X-ray radiation and gyrosynchrotron emission at microwaves. Those microwave bursts that were recorded at hard X-rays during CGRO-BATS observing times are discussed in more detail.

TAKALO L O, SILLANPÄÄ A, PURSIMO T, LEHTO H J, NILSSON K, TEERIKORPI P, HEINÄMÄKI P, LAINELA M, KIDGER M, DE DIEGO J A, GONZçLEZ-PÄREZ, RODRÊGUEZ-ESPINOSA J-M, MAHONEY T, BOLTWOOD P, DULTZIN-HACYAN D, BENÕTEZ E, TURNER G W, ROBERTSON J W, HONEYCUT R K, EFIMOV YU S, SHAKHOSKOY N, CHARLES P A, SCHRAMM K J, BORGEEST U, LINDE J V, WENEIT W, KÖHL D, SCHRAMM T, SADUN A, GRASHUIS R, HEIDT J, WAGNER S, BOCK H., KMMEL M, PFEIFFER M, HEINES A, FIORUCCI M, TOSTI G, GHISELLINI G, RAITERI C M, VILLATA M, DE FRANCESCO G, BOSIO S, LATINI G, POYNER G, ALLER M F, ALLER H D, HUGHES P, VALTAOJA E, TERÄSRANTA H, TORNIKOSKI M: "Monitoring of 3C 66A during an extended outburst. I The light curves; Astronomy and Astrophysics Supplement Series, Vol 120, pp 313-321, 1996. Abstract: We present results from a two year intensive monitoring of BL Lac object 3C 66A (PKS 0219+428). This object was observed in outburst during these two years. It reached the brightest ever observed magnitude on V=13.59 (1.2.1995) and on K=10.59 (15.2.1994). The optical and infrared light curves are characterised by randomly distributed fast flares, lasting a few days and well defined outbursts lasting a week or two. On top of these flares we can occasionally se small amplitude microvariability. No clear correlation can be found between the spectral behaviour and the occurrence of these flares. In the radio bands 3C 66A was quite faint and very stable compared to the optical variations. The light curves will be presented with preliminary analysis and discussions on the possible causes for the observed variations.

VALTAOJA E, TERÄSRANTA H: The relationsship between gamma emission and radio flares in AGN; Astronomy and Astrophysics Supplement Series, Vol 120, pp 491-494, 1996. Abstract: A comparison between Phase 1 EGRET data and Metsähovi total flux density monitoring at 22 GHz and 37 GHz shows that gamma-rays are likely to be detected only in quasars with high optical polarization, and even them only during the initial stages of a high radio frequency outburst. Other types of sources, including BL Lacs, are rarely detected. There also appears to be a correlation between the radio flare strength, rapidity, and the detected gamma-ray flux. Taken together, these results indicate that gamma-rays are produced by the synchrotron self-Compton mechanism in the shocked regions of the jet, with both the relativistic electrons and the seed photons originating in the same shock far away from the core and the accretion disk.

BRAJSA B, RUZDJAK V, VRSNAK B, WÖHL H, POHJOLAINEN S, URPO S: A new method for numerical data reduction of solar microwave measurements; Hvar Observatory Bulletin, Vol 20, pp 15-40, 1996. Abstract: Numerical data reduction of full-disk solar measurements taken in the microwave part of the spectrum (37 GHz) at the Metsähovi Radio Research Station is described. The basic parameteer distinguishing between various features on the microwave solar maps is the brightness temperature. Regions on the Sun with a lower brightness temperature than the quiet Sun level are called Low Temperature Regions (LTRs), and in the present paper mainly LTRs are considered. On the other hand, High Temperature Regions (HTRs) have a brightness temperature higher than the quiet Sun level. The data reduction includes: to obtain a circular solar picture, to construct twelve radial vectors from the preliminary solar disk center in order to determine the coordinates of the solar limb, to remove "erroneous" limb points, to determine a circle through the limb points by the least-squares method, to obtain corrected coordinates of the solar disk center and the radius and to repeat the procedures using the obtained results as input parameters. The quiet Sun level was determined as the mean value of all data points on the disk for every map separately. Several numerical criteria were tested, and the minima of relative intensities for all data points were determined. taking these minima as centers, circles of different radii were drawn with the criterion that the mean value inside the circle is less than the quiet Sun level. The latitudinal distribution of LTRs, as well as the solar rotation rate is determined by the LTRs, were investigated using automatic numerical procedures. It was established how the parameters which describe the solar rotation rate and corresponding errors depend upon various numerical criteria including: definition of LTR's size, allowing different deviations of LTR's position and rotation rate, confining the set of obtained rotation rates according to each error of the rotation rate and confining the set of obtained rotation rates according to allowance of a specific rotation rate at a specific latitude.

LILJESTRÖM T, OLOFSSON G: Evidence for infall toward Z Canis Majoris from radio and near-infrared spectroscopy;Astrophysical Journal, Vol 478, pp 1997.Abstract: We report radio line observations of CO(1-0), 13CO(1-0), CS(5-4), CS(2-1), C34S(2-1), H13CO+(1-0), HCS+(2-1), and N2H+(1-0) and near-infrared spectroscopy (in the K, L, and M bands) of Z CMa and its surroundings. Our results show that the CS(2-1) cloud around Z CMa is in approximate virial equilibrium and has a mass of some 42 M. The CS(5-4), C34S(2-1), and H13CO+(1-0) data reveal a centrally condensed and flattened inner cloud core structure perpendicular to the CO(1-0) outflow, which has a dynamical timescale of some (2*10^3)-(1*10^4) yr. The mass of the CS(5-4) core is 8.0-15 M, which is close to the magnetic critical mass. Along the major axis of the CS(5-4) core there is a velocity gradient, which can be interpreted as a superposition of initial cloud rotation and infall. Evidence for an infalling inner cloud core with a temperature gradient, an r^-1.5 density law, and an r^-0.5 velocity law is provided by the redshgift self-absorption feature in the H13CO+ profile, present in a very compact region oriented perpendicularly to the CO(1-0) outflow of Z CMa. Motivated by these signs of infall in the inner cluod core, we probe with our observational data the inside-out collapse model of Shu and the predictions of Galli & Shu for the collapse of a magnetized cloud core.
Our medium-resolution K-band spectrum shows besides the redshift, very marginal Brgamma line four vibrationally excited first-overtone CO band heads in absorption. The slopes seen in the K-band spectrum are intrinsic to the FU Orionis-type disk of Z CMa and suggest the presence of the vibration-rotation bands of water vapor, implying a temperature around 2000 K and a hydrogen nuclei density on the order of 10^12 cm^-3 at 2.2 micrometre. The likely cause of these water-band wings is the strong heating produced by the mass accretion through the inner disk onto the star. Our L band does not show the 3.08 micrometre water ice feature. Instead, our spectrum suggests the presence of a 2.9 micrometre feature, probably due to stretching vibrations of OH, or a shift of the water ice band to 2.9 micrometre, caused by large grains when scattering dominates.

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Metsähovi Radio Observatory / Abstracts

Metsähovi Radio Observatory /
Abstracts