The spectral indices in the optical continuum of the QSOs, BL Lacertae objects and the nuclei of Seyfert, N and normal galaxies

1981 ◽  
Vol 75 (2) ◽  
pp. 473-499 ◽  
Author(s):  
R. K. Thakur ◽  
R. K. Sood
Keyword(s):  
Spectral Indices ◽  
Bl Lacertae Objects ◽  
Normal Galaxies ◽  
Bl Lacertae ◽  
Optical Continuum

scholarly journals The Rosat X-Ray Spectra of BL Lacertae Objects

1996 ◽  
Vol 175 ◽  
pp. 267-268
Author(s):  
Paolo Padovani ◽  
Paolo Giommi
Keyword(s):  
Spectral Information ◽  
Spectral Indices ◽  
Bl Lacertae Objects ◽  
X Ray ◽  
Bl Lacertae ◽  
Bl Lac ◽  
Bl Lacs ◽  
Selection Of

We have analyzed the X-ray spectra of all BL Lacs observed (as pointed or serendipitous sources) by ROSAT. Spectral indices were obtained from the hardness ratios given in the WGA catalogue, a large list of X-ray sources generated from all the ROSAT PSPC pointed observations. The selection of the objects was done by cross-correlating the first revision of the WGA catalogue with our recent catalogue of BL Lacs. This resulted in 163 observations of 85 distinct BL Lacs, which correspond to about half the confirmed BL Lacs presently known. This represents the largest number of BL Lacs for which homogeneous X-ray spectral information is available and the largest BL Lac sample ever studied at X-ray frequencies.

scholarly journals ROSAT Observations of Bright BL Lacertae Objects

1994 ◽  
Vol 159 ◽  
pp. 377-377
Author(s):  
G. Lamer ◽  
H. Brunner ◽  
R. Staubert
Keyword(s):  
Power Laws ◽  
Spectral Indices ◽  
Bl Lacertae Objects ◽  
Mean Values ◽  
X Ray ◽  
Bl Lacertae ◽  
Spectrum Radio ◽  
Significant Difference ◽  
The Mean ◽  
5 Ghz

We have compiled a sample of 23 X-ray and radio selected BL Lacertae objects which have been observed with the Position Sensitive Proportional Counter (PSPC) on board of the ROSAT Satellite. The sample consists of three parts:In Table I results from 4 objects observed for their known rapid X-ray variability are presented. 5 objects are the BL Lac subset of a complete sample of flat spectrum radio sources with 5 GHz flux densities > 1 Jy. Detailed results from this sample will be published in Brunner et al. 1993. The data of the 14 remainig objects were collected from the ROSAT data archive to supplement the sample. The whole sample contains 7 X-ray selected objects (XBLs,αOX < 1.2) and 16 radio selected objects (RBLs).The X-ray spectra of the sources are well described by single power laws with galactic absorption. The X-ray energy indices αX are widely dispersed around a mean of 1.34. Significant X-ray flux variability and correlated spectral variability was detected on timescales down to hours. The object H 1218+304 was found to be rapidly variable within each of three observations. Its spectral hardness is correlated with the flux level (see Table I).We calculated the intrinsic distributions of the spectral indices αX for the XBL and RBL samples and of the differences between ROSAT and EXOSAT ME spectral indices αPSPC – αME (only XBL sample) using a maximum likelihood fit. There is no significant difference in the mean spectral indices between the X-ray and radio selected subsamples. The mean values < αX > are 1.34 for XBLs and 1.33 for RBLs. The spectra of the X-ray selected objects slightly steepen at higher X-ray energies (< αPSPC – αME > = −0.11). This supports the view that the X-ray emission of XBLs is supplied by synchrotron radiation. The steepening of the X-ray spectrum is then due to a cutoff in the energy distribution of the electrons.

scholarly journals Astrophysical implications of binary black holes in BL Lacertae objects

2002 ◽  
Vol 388 (2) ◽  
pp. 470-476 ◽  
Author(s):  
F. De Paolis ◽  
G. Ingrosso ◽  
A. A. Nucita
Keyword(s):  
Black Holes ◽  
Bl Lacertae Objects ◽  
Binary Black Holes ◽  
Bl Lacertae

scholarly journals Longterm optical monitoring of bright BL Lacertae objects with ATOM: Spectral variability and multiwavelength correlations

2014 ◽  
Vol 573 ◽  
pp. A69 ◽  
Author(s):  
Alicja Wierzcholska ◽  
Michał Ostrowski ◽  
Łukasz Stawarz ◽  
Stefan Wagner ◽  
Marcus Hauser
Keyword(s):  
Optical Monitoring ◽  
Spectral Variability ◽  
Bl Lacertae Objects ◽  
Bl Lacertae

scholarly journals Polarization VLBI Observations of a Complete Sample of Northern BL Lacertae Objects

1998 ◽  
Vol 164 ◽  
pp. 165-166
Author(s):  
A. B. Pushkarev ◽  
D. C. Gabuzda
Keyword(s):  
Magnetic Field ◽  
Radio Emission ◽  
Synchrotron Emission ◽  
Complete Sample ◽  
Bl Lacertae Objects ◽  
Bl Lacertae ◽  
Vlbi Observations ◽  
Core Components ◽  
Jet Structure ◽  
The Magnetic Field

AbstractThe polarization electric vectors in the VLBI jets of BL Lacertae objects are typically aligned with the jet structure. If the jet radio emission is optically thin synchrotron emission, this implies that the magnetic field is perpendicular to the jet, usually interpreted as a signature of shocks. The distribution of polarization position angles in the VLBI core components appears to be bimodal, with the polarization angles either aligned with or perpendicular to the jet direction. In order to study the origin of this characteristic polarization structure, we have made VLBI polarization observations of all 34 sources in the Kühr and Schmidt sample of BL Lacertae objects.

scholarly journals Host galaxy subtraction of TeV candidate BL Lacertae objects

2007 ◽  
Vol 475 (1) ◽  
pp. 199-207 ◽  
Author(s):  
K. Nilsson ◽  
M. Pasanen ◽  
L. O. Takalo ◽  
E. Lindfors ◽  
A. Berdyugin ◽  
...  
Keyword(s):  
Host Galaxy ◽  
Bl Lacertae Objects ◽  
Bl Lacertae

scholarly journals The intraday variability in the radio-selected and X-ray-selected BL Lacertae objects

1998 ◽  
Vol 132 (1) ◽  
pp. 83-92 ◽  
Author(s):  
J. M. Bai ◽  
G. Z. Xie ◽  
K. H. Li ◽  
X. Zhang ◽  
W. W. Liu
Keyword(s):  
Bl Lacertae Objects ◽  
X Ray ◽  
Bl Lacertae ◽  
Intraday Variability
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