scholarly journals Evidence for Relativistic Motion in the Millisecond Structure of BL Lac

1982 ◽  
Vol 97 ◽  
pp. 385-386 ◽  
Author(s):  
R. L. Mutel ◽  
R. B. Phillips
Keyword(s):  
Position Angle ◽  
West Germany ◽  
Relativistic Motion ◽  
Owens Valley ◽  
Vlbi Observations ◽  
Bl Lac ◽  
5 Ghz

After several years of relative quiescence, the flux of BL Lac has increased dramatically at centimeter wavelength, starting about epoch 1979.9 (Fig. 1). We have begun a series of VLBI observations to monitor the milliarcsecond structure at λ6 and λ2.8 cm wavelengths, using a five element VLBI array consisting of telescopes at Bonn, West Germany; Westford, MA; Green Bank, WV; Ft. Davis, TX; and Owens Valley, CA. The first two observations, in 1980 May and September, were at 5 GHz and were not of sufficient resolution to distinguish individual components in the source (Mutel, Phillips and Aller 1981). They did show, however, that the source was highly elongated along position angle ∼ 10° and was expanding that axis with a velocity of ∼4 c. The position angle is the same as several previous VLBI observations of this source, both during quiet periods and during previous flux outbursts (Pearson and Readhead 1981; Shaffer 1978 and references therein).

scholarly journals Bulk Relativistic Motion in a Complete Sample of Flat Spectrum Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 71-72
Author(s):  
C. J. Schalinski ◽  
A. Witzel ◽  
Th.P. Krichbaum ◽  
C. A. Hummel ◽  
P. L. Biermann ◽  
...  
Keyword(s):  
Flux Density ◽  
Status Report ◽  
Radio Sources ◽  
Supporting Evidence ◽  
X Rays ◽  
Relativistic Motion ◽  
Bl Lac Objects ◽  
Vlbi Observations ◽  
Wide Range ◽  
5 Ghz

As part of a multi-epoch and multi-wavelength study of the physics of core dominated radio sources we have investigated the occurrence of apparent superluminal motion and other indications for bulk relativistic motion (b.r.m) in a statistically complete, flux density limited (S5GHz ≥ 1Jy) sample of 13 objects with flat radio spectra These sources come from the S5-survey (Kühr et al., 1981) and are optically identified as 7 quasars and 6 BL-Lac objects. They have been observed over a wide range of frequencies, from radio through X-rays (s. Eckart et al., 1986 and references therein). Radiomaps have been obtained at frequencies from 327 MHz to 22.2 GHz with resolutions from arcseconds to 0.2 mas, using the VLA, MERLIN and telescopes of the US- and European-VLBI networks. A recent status report on the VLBI-observations is given by Witzel (1987). In this paper we summarize the results on the direct evidence for b.r.m. in this sample as derived from repeated VLBI-observations at 5 GHz, as well as supporting evidence from SSC-calculations and flux density variability of the 5GHz VLBI core components (Table 1).

scholarly journals Serendipitous VLBI Observations of Intraday Variability in the BL Lac Objects 1334–127, 2131–021, and 2155–152

1998 ◽  
Vol 164 ◽  
pp. 273-274
Author(s):  
P. Yu. Kochanev ◽  
D. C. Gabuzda
Keyword(s):  
Rapid Variability ◽  
Bl Lac Objects ◽  
Polarization Structure ◽  
Vlbi Observations ◽  
Bl Lac ◽  
Vlbi Data ◽  
Intraday Variability

AbstractGlobal λ = 6 cm VLBI polarization observations of intraday variability in the three BLLacertae objects 1334–127, 2131–021, and 2155–152 are analyzed. Integrated VLA measurements during the VLBI observations show that although there were no substantial total intensity variations, the polarizations for these three sources varied significantly during the VLBI experiment. The VLBI data were divided into 2-3 hour segments in order to search for corresponding rapid variability in the VLBI polarization structure. Our analysis shows that the VLA polarization variability in 2155–152 and 2131–021 is present in the VLBI data (i.e., it occurred on mas scales), but this is not the case for 1334–127.

Radio continuum of galaxies with H2O megamaser disks

2017 ◽  
Vol 13 (S336) ◽  
pp. 139-140
Author(s):  
F. Kamali ◽  
C. Henkel ◽  
A. Brunthaler ◽  
C. M. V. Impellizzeri ◽  
K. M. Menten ◽  
...  
Keyword(s):  
Black Hole ◽  
Accretion Disk ◽  
Active Galactic Nucleus ◽  
Position Angle ◽  
Radio Continuum ◽  
Supermassive Black Hole ◽  
5 Ghz

AbstractIn our attempt to investigate the basic active galactic nucleus (AGN) paradigm requiring a centrally located supermassive black hole (SMBH), a close to Keplerian accretion disk and a jet perpendicular to its plane, we have searched for radio continuum in galaxies with H2O megamasers in their disks. We observed 18 such galaxies with the Very Large Baseline Array in C band (5 GHz, ~2 mas resolution) and we detected 5 galaxies at 8 σ or higher levels. For those sources for which the maser data is available, the positions of masers and those of the 5 GHz radio continuum sources coincide within the uncertainties, and the radio continuum is perpendicular to the maser disk’s orientation within the position angle uncertainties.

scholarly journals The Milliarcsecond Structure of Active Galactic Nuclei Observed with VLBI

1989 ◽  
Vol 134 ◽  
pp. 525-528
Author(s):  
T. J. Pearson ◽  
A. C. S. Readhead
Keyword(s):  
Active Galactic Nuclei ◽  
Very Long Baseline Interferometry ◽  
Galactic Nuclei ◽  
Radio Galaxies ◽  
Relativistic Motion ◽  
Powerful Radio ◽  
Long Baseline ◽  
Vlbi Observations ◽  
Central Engine

Very Long Baseline Interferometry at radio wavelengths is the only technique available for imaging the central few parsecs of powerful radio galaxies and quasars. VLBI observations have shown that in many nuclei radio-emitting material is collimated into a jet on a scale less than a parsec and ejected at relativistic velocities. The interpretation of the observations is complicated by the relativistic motion, however: the images are dominated by those parts of the source that are moving almost directly towards the observer, and thus amplified by relativistic aberration. Nonetheless, the VLBI images are vital for understanding the nature of the central engine, the cause of the collimation, and the physics of the jets.

scholarly journals A CCD survey of BL Lac objects

1986 ◽  
Vol 119 ◽  
pp. 125-126
Author(s):  
Helmut Kuhr ◽  
Josef Fried
Keyword(s):  
Optical Spectroscopy ◽  
Max Planck ◽  
Complete Sample ◽  
Bl Lac Objects ◽  
Ccd Imaging ◽  
Bl Lac ◽  
5 Ghz ◽  
Spectroscopy Optical

A long term project was started at the Max-Planck-Institut fur Astronomie, Heidelberg, to study a complete sample of 46 northern and southern BL Lac objects with flux densities exceeding 1 Jy at 5 GHz using optical spectroscopy, optical polarimetry, and direct deep CCD imaging.

scholarly journals Frequency Dependence of the Parsec-scale Polarization Structures of BL Lac Objects

2001 ◽  
Vol 205 ◽  
pp. 140-141
Author(s):  
A.B. Pushkarev ◽  
D.C. Gabuzda ◽  
T.V. Cawthorne
Keyword(s):  
Line Emission ◽  
Galactic Nuclei ◽  
Optical Emission ◽  
Bl Lac Objects ◽  
Bl Lacertae ◽  
Sky Survey ◽  
Radiation Sources ◽  
Wide Wavelength Range ◽  
Bl Lac ◽  
5 Ghz

BL Lacertae objects are active galactic nuclei with weak or undetectable line emission and strong variability in total intensity and linear polarization over a wide wavelength range from optical to radio. The radio emission and much of the optical emission is believed to be synchrotron radiation. Sources in the complete sample of BL Lac objects defined by Kühr and Schmidt (1990) have: 5 GHz fluxes of at least 1 Jy, radio spectral index α ≥ −0.5 (Sv ˜ v+α), rest frame equivalent width of the strongest emission lines less than 5 Å, and optical counterparts on the Sky Survey plates with brightness greater than 20m.

scholarly journals Mark III VLBI Observation of Pulsars

1984 ◽  
Vol 110 ◽  
pp. 275-276 ◽  
Author(s):  
N. Bartel ◽  
R. J. Cappallo ◽  
M. I. Ratner ◽  
A.E.E. Rogers ◽  
I. I. Shapiro ◽  
...  
Keyword(s):  
West Germany ◽  
Vlbi Observation ◽  
Signal To Noise ◽  
Vlbi Observations ◽  
Interferometric Investigation ◽  
Pulse Structure

Mark III VLBI observations of the pulsars PSR 0329+54 and PSR 1133+16 were made at 2.3 GHz using antennas with diameters and locations as follows: 100m, Effelsberg, West Germany (but only for SPR 0329+54); 43m Green Bank, WV, USA; and 40m, Big Pine, CA, USA. The Mark III processor at the Haystack Observatory was “gated” to compute visibility amplitudes and phases as a function of pulsar longitude. This method allowed a) an improvement of the signal to noise ration, by as much as a factor of ten in the case of PSR 1133+16, and b) an interferometric investigation of the pulse structure.

scholarly journals 3C 216: Is It the CSS Source with the Highest Rotation Measure?

1998 ◽  
Vol 164 ◽  
pp. 183-184
Author(s):  
E. Lüdke ◽  
W. D. Cotton ◽  
H. S. Sanghera ◽  
D. Dallacasa
Keyword(s):  
Faraday Rotation ◽  
Position Angle ◽  
Angle Variation ◽  
Strong Polarization ◽  
Self Calibration ◽  
Rotation Measure ◽  
5 Ghz ◽  
Starting Model

AbstractWe discuss our VLBA observations at 5 and 2.7 GHz and our MERLIN observations at 1.6 and 5 GHz. A MERLIN+VLBA image provided good starting model for self-calibration and we obtained an unprecedent image of the bent jet of 3C 216. Our observations suggest the detection of strong polarization position angle variation across the observing band. If this is due to Faraday rotation then 3C216 may have a four-figure observed rotation measure, which is unlikely to be due to errors in the polarization position angle calibration.

Sign in / Sign up

Export Citation Format

Share Document