scholarly journals The radio structure of the BL Lac-type object 3C 66A

1981 ◽  
Vol 194 (4) ◽  
pp. 919-925 ◽  
Author(s):  
D. Stannard ◽  
M. R. Edwards ◽  
B. K. McIlwrath
Keyword(s):  
Radio Structure ◽  
Bl Lac ◽  
Type Object

scholarly journals Sub-milliarcsecond Radio Structure of AO 0235+164

1984 ◽  
Vol 110 ◽  
pp. 47-48
Author(s):  
Dayton L. Jones ◽  
Mike M. Davis ◽  
Steve C. Unwin
Keyword(s):  
Optical Absorption ◽  
Flux Density ◽  
Radio Spectrum ◽  
Absorption Lines ◽  
Radio Structure ◽  
Spectrum Radio ◽  
Bl Lac ◽  
Line Redshift ◽  
To Come ◽  
Absorption Frequencies

AO 0235+164 is a very compact, flat-spectrum radio source. It is identified with a BL Lac object, and has optical absorption-line systems at z = 0.524 and z = 0.852. A complex set of HI absorption lines is seen at z = 0.524 (932 MHz), and several of these lines change significantly in depth over periods of less than a year. This is the only known case of variable extragalactic absorption lines. A faint nebulosity 2 arcsec south of AO 0235 + 164 has an emission-line redshift of z = 0.52 and may be an intervening galaxy. The radio spectrum of this source (between major outbursts) is remarkably flat, with the total flux density staying between about 1 and 3 Jy over a range of at least 1000 in frequency. Such a flat spectrum would lead one to expect a complex, wavelength-dependent structure consisting of several components with different self-absorption frequencies. However, the observed radio structure of 0235+164 is about as simple as one could imagine – it is a nearly unresolved point source in VLBI experiments from 900 MHz to 22 GHz. Recent VLBI experiments at 6 and 13 cm have shown evidence for some elongation of the source in a generally NE-SW direction, but only at low contour levels (< 15% of the peak). The major portion of the flux density appears to come from a core which is unresolved in VLBI experiments over a range of ~ 25 in frequency.

scholarly journals Optical Spectropolarimetry Observations of the BL Lac-type object PKS 0537-441 after a period of quiescence

2021 ◽  
Author(s):  
Joleen Barnard ◽  
Brian van Soelen ◽  
Justin Cooper ◽  
Richard Britto ◽  
Johannes Petrus Marais ◽  
...  
Keyword(s):  
Bl Lac ◽  
Type Object

The radio structure of BL Lac object S5 2007+777

2010 ◽  
Vol 53 (S1) ◽  
pp. 187-190
Author(s):  
ZhongZu Wu ◽  
MinFeng Gu ◽  
YongJun Chen
Keyword(s):  
Radio Structure ◽  
Bl Lac

Unusual properties of the radio structure of the BL Lac object 1749+701 on parsec scales

2009 ◽  
Vol 53 (1) ◽  
pp. 51-58 ◽  
Author(s):  
D. C. Gabuzda ◽  
M. M. Lisakov
Keyword(s):  
Radio Structure ◽  
Bl Lac

scholarly journals EVN Observations of BL Lac Objects with Distorted Structures

1998 ◽  
Vol 164 ◽  
pp. 161-162
Author(s):  
P. Chariot ◽  
H. Sol ◽  
L. Vicente
Keyword(s):  
Radio Emission ◽  
Bl Lac Objects ◽  
Radio Structure ◽  
Bl Lac

AbstractWe present results of observations of two BL Lac objects, 0735+178 and 0723–008, with the European VLBI Network (EVN) at 1.7 GHz. These objects have a distorted morphology, characterized by a large misalignment between their inner and outer radio structures. Our EVN observations at intermediate resolution reveal the presence of a highly curved jet in 0735+178, providing evidence for continuity of the radio emission from milliarcsecond to arcsecond scales. No indication of connecting radio structure is found in the case of 0723–008.

Extended radio structure of BL Lac type objects

Nature ◽  
1982 ◽  
Vol 298 (5870) ◽  
pp. 140-142 ◽  
Author(s):  
D. Stannard ◽  
B. K. McIlwrath
Keyword(s):  
Radio Structure ◽  
Extended Radio ◽  
Bl Lac

scholarly journals Distortion Effects in BL Lac Radio Jets

1996 ◽  
Vol 175 ◽  
pp. 477-478 ◽  
Author(s):  
H. Sol ◽  
S. Appl ◽  
L. Vicente
Keyword(s):  
Large Scale ◽  
Lorentz Factor ◽  
Radio Sources ◽  
Misalignment Angle ◽  
Bl Lac Objects ◽  
Radio Structure ◽  
Radio Jets ◽  
Bl Lac ◽  
Different Types ◽  
Bl Lacs

BL Lac objects often show a quite distorted radio morphology. Almost 75% of the BL Lacs for which the information is available show an apparent misalignment angle ΔPA between the VLBI jet and the large scale radio structure larger than 45 degrees. This can be explained by strong enhancement of slight bending due to projection effects, especially if BL Lacs are the most highly beamed sources. However we recently performed a statistical analysis of misalignment angle histograms for 155 extragalactic radio sources of different types and found that the intrinsic distortion is significantly more important in BL Lacs than in quasars and even CSS sources. Indeed the best fits of the δPA histograms by a simple bend model correspond to γɸ = 123° for BL Lacs, 37° for quasars and 36° for CSS sources, where ɸ and γ are the jet typical intrinsic bend and Lorentz factor within a given class of sources (Appl et al, 1995). If, as currently thought, jets in BL Lacs have smaller Lorentz factors than in quasars, high intrinsic bending and misalignment appear to be the rule in BL Lac sources.

scholarly journals Gaia-assisted discovery of a detached low-ionisation BAL quasar with very large ejection velocities

2020 ◽  
Vol 634 ◽  
pp. A111 ◽  
Author(s):  
J. P. U. Fynbo ◽  
P. Møller ◽  
K. E. Heintz ◽  
J. N. Burchett ◽  
L. Christensen ◽  
...  
Keyword(s):  
Emission Line ◽  
Absorption Line ◽  
Emission Lines ◽  
Broad Absorption ◽  
Broad Absorption Line ◽  
Red Edge ◽  
First Case ◽  
Bl Lac ◽  
Spatially Extended ◽  
Extended Emission

We report on the discovery of a peculiar broad absorption line (BAL) quasar identified in our Gaia-assisted survey of red quasars. The systemic redshift of this quasar was difficult to establish because of the absence of conspicuous emission lines. Based on deep and broad BAL troughs of at least Si IV, C IV, and Al III, a redshift of z = 2.41 was established under the assumption that the systemic redshift can be inferred from the red edge of the BAL troughs. However, we observe a weak and spatially extended emission line at 4450 Å that is most likely due to Lyman-α emission, which implies a systemic redshift of z = 2.66 if correctly identified. There is also evidence for the onset of Lyman-α forest absorption bluewards of 4450 Å and evidence for Hα emission in the K band consistent with a systemic redshift of z = 2.66. If this redshift is correct, the quasar is an extreme example of a detached low-ionisation BAL quasar. The BALs must originate from material moving with very large velocities ranging from 22 000 km s−1 to 40 000 km s−1. To our knowledge, this is the first case of a systemic-redshift measurement based on extended Lyman-α emission for a BAL quasar. This method could also be useful in cases of sufficiently distant BL Lac quasars without systemic-redshift information.

scholarly journals A Comparison of the X-ray Spectra of Quasars and BL Lac Objects

1989 ◽  
Vol 134 ◽  
pp. 197-198
Author(s):  
D. M. Worrall ◽  
B. J. Wilkes
Keyword(s):  
Power Law ◽  
Radio Spectrum ◽  
Spectral Indices ◽  
Mean Power ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Infrared Frequencies

Quasars with similar core-compact radio properties can be classified by their differences at optical and infrared frequencies. Their X-ray properties might be expected to be similar if the synchrotron self-Compton mechanism relates their radio and X-ray emission. We have compared the 0.2–3.5 keV mean power-law energy spectral indices, , for 4 quasar classes: 12 Highly Polarized QSOs (HPQs), 19 Flat Radio Spectrum, core-compact, low-polarization, QSOs (FRS QSOs), 24 radio-selected BL Lac objects, and 7 X-ray-selected BL Lac objects.

Sign in / Sign up

Export Citation Format

Share Document