ALBERT

Description: The first detection of interference fringes by VLBI at a wavelength of 3.4 mm during observations of 3C84 are reported. The compact source in the nucleus of 3C84 was observed for a 9-hr period on the 485 km baseline between the Owens Valley Radio Observatory and the Hat Creek Observatory. The fringe data are given and the derivation of the correlated flux densities is described. The findings are discused in the context of previous obervations. The results demonstrate that there are no unforeseen technical difficulties associated with millimeter VLBI, and that the sensitivity of existing systems is sufficient to observe objects brighter than a few Jy. The observations are consistent with the millimeter wavelength radio structure of 3C84 being more compact than its centimeter wavelength structure.

Description: SS 433 was detected and partially resolved at 2290 MHz on baselines with fringe spacings of 1.4, 0.1, and 0.003 arcsec. It was also detected at 8420 MHz on a baseline with a fringe spacing of 0.009 arcsec. Simple models of the source, consistent with the limited data, have elongated structures greater than 0.1 arcsec in size with position angles in 1979 May that were within about 10 deg of the position angle of the apparent bulges of the supernova remnant W50. The data also imply that the source contains a core less than 0.002 arcsec in size with a brightness temperature greater than 10 to the 9th K. The bright core and aligned structures that seem to be present in SS 433 and W50 resemble the structures seen in powerful extragalactic radio sources which are many orders of magnitude larger.

Description: The radio structure of the quasar 3C147 has been determined from multi-baseline VLBI data at 609 MHz using both a conventional method and a technique which uses the 'closure' phase information to produce a good approximation to a synthesis map of the source. The structure is similar to the central part of M87, with a bright core and a linear 'jet' of a projected length of about 1.5 kpc which is concentrated in bright 'knots'.

Description: We present the first results of observations of the intrinsic anisotropy of the cosmic microwave background radiation with the Cosmic Background Imager from a site at 5080 in altitude in northern Chile. Our observations show a sharp decrease in C_l in the range l = 400 - 1500. Such a decrease in power at high l is one of the fundamental predictions of the standard cosmological model, and these are the first observations which cover a broad enough 1-range to show this decrease in a single experiment. The power, C_l, at l approximately 600 is higher than measured by Boomerang and Maxima, with the differences being significant at the 2.7sigma and 1.9sigma levels, respectively. The C_l we have measured enable us to place limits on the density parameter, Omega(tot) 〈= 0.4 or Omega(tot) 〉= 0.7 (90% confidence).

Description: Spectroscopic observations of 13 Seyfert 1 galaxies made from 1979 to 1984 at Palomar and Steward Observatories were analyzed for H beta line profile variations. Significant profile changes were detected in five galaxies. These variations are often associated with changes in continuum and/or H beta strength, suggesting a causal connection between variations in the continuum source and changes in emission-line profiles. Moreover, the overall strength of H beta line flux variations is strongly correlated with line width in the far wings, whereas no such correlation was found in the line core. This finding is consistent with previous observations (Shuder 1982) which suggest that higher velocity gas lies closer to the central continuum source, since this inner gas would be expected to track variations more closely. In each of the five galaxies in which H beta line profile variations were detected, particularly NGC 5548 and Mrk 6, only two distinct line profile shapes were observed. Since intermediate profile types were not detected, the transition from one type to the other must occur rapidly (within a few months). These rapid line profile variations are thus consistent with numerous other studies which strongly point to a small broad-line region (BLR) size in Seyfert galaxies. Observational models of BLR kinematics and structure for each of the galaxies in the present sample are presented. Line asymmetries suggest that radial motions exist in the BLRs of most of these objects. Chaotic motions also appear to be quite common. However, evidence for rotational motion was observed in only one case. A model that is consistent with the majority of this sample incorporates both radial and chaotic motions combined with some form of external obscuration such as an optically and geometrically thick torus.

Description: The radio properties of blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope have been observed as part of the VLBA Imaging and Polarimetry Survey. This large, flux-limited sample of active galactic nuclei (AGNs) provides insights into the mechanism that produces strong gamma-ray emission. At lower flux levels, radio flux density does not directly correlate with gamma-ray flux. We find that the LAT-detected BL Lac objects tend to be similar to the non-LAT BL Lac objects, but that the LAT-detected FSRQs are often significantly different from the non-LAT FSRQs. The differences between the gamma-ray loud and quiet FSRQS can be explained by Doppler boosting; these objects appear to require larger Doppler factors than those of the BL Lac objects. It is possible that the gamma-ray loud FSRQs are fundamentally different from the gamma-ray quiet FSRQs. Strong polarization at the base of the jet appears to be a signature for gamma-ray loud AGNs.

Description: A complete sample of double-lobed 3CR quasars with minimal orientation bias is defined. Properties of these objects on the greater than kpc scale are consistent with the simple beaming model for their nuclei. VLBI maps of six nuclei reveal 'core-jet' structures. Both nuclei mapped at multiple epochs are modestly superluminal. The distribution of apparent velocities in this sample will provide a stringent test of beaming.

Description: If the simple relativistic beaming model for extragalactic radio sources is at all correct, Doppler boosting may bias us toward choosing those objects pointing nearly at us in flux-density limited samples. In order to minimize any such effects in statistical tests of physical theories of these objects, an attempt is made to define a complete sample of sources with random orientations. For a sample of 26 double-lobed quasars, the dependence of a number of observable features on the angle to the line of sight and on the superluminal velocity is examined, and the distribution of superluminal velocities for the sources is measured. Two new superluminals are reported, and their apparent velocities and nuclear strengths are discussed.

Description: We report on multifrequency observations performed during 2012 December-2013 August of the first narrow-line Seyfert 1 galaxy detected in gamma rays, PMN J0948+0022 (z equal to 0.5846). A gamma-ray flare was observed by the Large Area Telescope on board Fermi during 2012 December-2013 January, reaching a daily peak flux in the 0.1-100 GeV energy range of (155 plus or minus 31)10(exp 8) ph cm (exp 2) s (exp 1) on 2013 January 1, corresponding to an apparent isotropic luminosity of approximately 1.510)exp 48) erg s(exp 1). The gamma-ray flaring period triggered Swift and VERITAS observations in addition to radio and optical monitoring by OVRO, MOJAVE, and CRTS. A strong flare was observed in optical, UV, and X- rays on 2012 December 30, quasi-simultaneously to the gamma-ray flare, reaching a record flux for this source from optical to gamma rays. VERITAS observations at very high energy (E greater than 100 GeV) during 2013 January 6-17 resulted in an upper limit of F(sub greater than 0.2 TeV) less than 4.0 10(exp 12) ph cm(exp 2) s(exp 1). We compared the spectral energy distribution (SED) of the flaring state in 2013 January with that of an intermediate state observed in 2011. The two SEDs, modelled as synchrotron emission and an external Compton scattering of seed photons from a dust torus, can be modelled by changing both the electron distribution parameters and the magnetic field.

Description: A complete, flux-density-limited sample of double-lobed radio quasars is defined, with nuclei bright enough to be mapped with the Mark III VLBI system. It is shown that the statistics of linear size, nuclear strength, and curvature are consistent with the assumption of random source orientations and simple relativistic beaming in the nuclei. However, these statistics are also consistent with the effects of interaction between the beams and the surrounding medium. The distribution of jet velocities in the nuclei, as measured with VLBI, will provide a powerful test of physical theories of extragalactic radio sources.