Optical polarization models of quasi-stellar objects and BL Lac objects.

1976 ◽  
Vol 209 ◽  
pp. 653 ◽  
Author(s):  
K. H. Nordsieck
Keyword(s):  
Optical Polarization ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Bl Lac ◽  
Quasi Stellar Objects ◽  
Polarization Models

Optical spectroscopy of BL Lac objects: TeV candidates

2020 ◽  
Vol 497 (1) ◽  
pp. 94-108 ◽  
Author(s):  
Simona Paiano ◽  
Renato Falomo ◽  
Aldo Treves ◽  
Riccardo Scarpa
Keyword(s):  
Lower Limit ◽  
Gamma Ray ◽  
Absorption Lines ◽  
Host Galaxies ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Forbidden Transition ◽  
Bl Lac ◽  
Quasi Stellar Objects ◽  
Relationship Of

ABSTRACT We investigate the spectroscopic optical properties of gamma-ray sources detected with high significance above 50 GeV in the Third Catalog of Hard Fermi-LAT Sources and that are good candidates as TeV emitters. We focus on the 91 sources that are labelled by the Fermi team as BL Lac (BLL) objects or blazar candidates of uncertain type (BCUs), are in the Northern hemisphere, and are with unknown or uncertain redshift. We report here on GTC (Gran Telescopio Canarias) spectra (in the spectral range 4100–7750 Å) of 13 BCUs and 42 BLL objects. We are able to classify the observed targets as BLL objects and each source is briefly discussed. The spectra allowed us to determine the redshift of 25 objects on the basis of emission and/or absorption lines, finding 0.05 < z < 0.91. Most of the emission lines detected are due to forbidden transition of [O iii] and [N ii]. The observed line luminosity is found to be lower than that of quasi-stellar objects (QSOs) at similar continuum and could be reconciled with the line–continuum luminosity relationship of QSOs if a significant beaming factor is assumed. Moreover, for five sources we found intervening absorption lines that allow to set a spectroscopic lower limit of the redshift. For the remaining 25 sources, for which the spectra are lineless, a lower limit to z is given, assuming that the host galaxies are giant ellipticals.

scholarly journals A new catalogue of quasi-stellar objects

1986 ◽  
Vol 119 ◽  
pp. 51-52
Author(s):  
A. Hewitt ◽  
G. Burbidge
Keyword(s):  
Seyfert Galaxies ◽  
List Type ◽  
Type Number ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
X Ray ◽  
Bl Lac ◽  
Similar Information ◽  
Quasi Stellar Objects ◽  
Objective Prism

We have prepared a new catalogue of QSOs and BL Lac objects containing approximately 3400 entries. A complete update of the Hewitt-Burbidge (1980) catalogue has been made with approximately another 2000 objects with known redshifts added. The references to discovery, magnitudes, redshifts, color, spectra and polarimetry have been updated for the objects listed in 1980, and complete new references are included for the new objects. In addition to the basic optical information, the new catalogue also contains X-ray, radio and infrared information for all objects. Absorption redshifts are listed when they are available. A supplementary catalogue which is now in preparation will contain similar information for objects described variously as Seyfert galaxies, N systems and AGNs. In doubtful cases we have used the operational dividing line ƶ = 0.1. All objects with ƶ < 0.1 are put in the supplementary catalogue unless their discoverers have unambiguously defined them as QSOs. With approximately twice as many objects included it is interesting to note that: a)There are still very few genuine BL Lac objects, ∼100.b)The largest number of additions has come from identifications using the objective prism-grism techniques.

scholarly journals New optical polarization measurements of quasi-stellar objects. The data

2005 ◽  
Vol 433 (2) ◽  
pp. 757-764 ◽  
Author(s):  
D. Sluse ◽  
D. Hutsemékers ◽  
H. Lamy ◽  
R. Cabanac ◽  
H. Quintana
Keyword(s):  
Optical Polarization ◽  
Stellar Objects ◽  
Polarization Measurements ◽  
Quasi Stellar Objects

Accurate Radio Positions with the Tidbinbilla Interferometer

1979 ◽  
Vol 3 (6) ◽  
pp. 400-402 ◽  
Author(s):  
M. J. Batty ◽  
David L. Jauncey ◽  
P. T. Rayner ◽  
S. Gulkis
Keyword(s):  
Absorption Spectra ◽  
High Redshift ◽  
Optical Emission ◽  
Radio Sources ◽  
Stellar Objects ◽  
Bl Lac Objects ◽  
Optical Position ◽  
Bl Lac ◽  
Compact Galaxies ◽  
Optical Identifications

Radio position measurements with an error of <2” arc rms allow reliable optical identifications of compact radio sources to be made solely on the basis of radio-optical position coincidence. In this way neutral or red stellar objects, faint compact galaxies and faint QSOs can be reliably identified. Such identifications are of particular interest because they are rich in BL Lac objects, high-redshift QSOs, QSOs with unusual optical emission or absorption spectra and galaxies with active nuclei (see Jauncey et al. 1978).

scholarly journals High Energy Phenomena in AGN Jets

1998 ◽  
Vol 188 ◽  
pp. 153-156
Author(s):  
F. Takahara
Keyword(s):  
Gamma Ray ◽  
High Energy ◽  
Line Of Sight ◽  
Time Variability ◽  
Optical Polarization ◽  
Bl Lac Objects ◽  
Relativistic Jet ◽  
Bl Lac ◽  
Gamma Ray Emission ◽  
Superluminal Expansion

BL-Lac objects and optically violent variable quasars (OVVs), called together blazars, are characterized by rapid time variability, strong optical polarization, superluminal expansion and strong gamma-ray emission. Such properties are understood in the framework of a relativistic jet emanated from the central powerhouse. Blazars are considered to be objects for which the direction of the jet is very close to the line of sight.

scholarly journals The Brightness and Polarization Structure of Compact Radio Sources

1988 ◽  
Vol 129 ◽  
pp. 161-162
Author(s):  
Raymond Rusk
Keyword(s):  
Position Angle ◽  
Active Galaxies ◽  
Radio Sources ◽  
Optical Polarization ◽  
Polarization Data ◽  
Core Component ◽  
Structural Position ◽  
Bl Lac Objects ◽  
The Core ◽  
Bl Lac

New VLA polarization data for 140 radio sources have been used to study the correlation between VLBI structural position angle and radio and optical polarization position angles reported in Rusk and Seaquist (1985). We confirm that there is a strong tendency, in active galaxies and quasars, for the radio E vector (of the core component) to lie normal to the VLBI structural axis. However, in BL Lac objects we find a tendency for the core radio E vector to be aligned parallel to the VLBI structural axis.

INVESTIGATION OF CORRELATIONS BETWEEN THE OPTICAL AND VLBI CORE POLARIZATION OF AGN

2008 ◽  
Vol 17 (09) ◽  
pp. 1537-1543
Author(s):  
J. C. ALGABA ◽  
D. C. GABUZDA ◽  
P. S. SMITH
Keyword(s):  
Synchrotron Radiation ◽  
Faraday Rotation ◽  
Clear Correlation ◽  
Polarization Angle ◽  
Optical Polarization ◽  
Core Polarization ◽  
Bl Lac Objects ◽  
Highly Active ◽  
Bl Lac ◽  
Very High

The continua of highly active radio-loud AGN are dominated by synchrotron radiation over virtually the entire spectrum. Despite this fact, it has often been thought that no correlation between optical and radio polarization should be observed, based on the idea that the synchrotron radiation at very different wavelengths is emitted at very different regions in the jet. However, a clear correlation between the Faraday-rotation-corrected VLBI core radio polarization angle and the nearly simultaneously measured optical polarization angle was found by Gabuzda et al., suggesting that the optical and compact radio polarizations are more closely related than had been thought. We have obtained new data in order to investigate this question. Our preliminary results show that, although the optical and radio core polarizations of BL Lac objects are usually aligned, the behavior displayed by quasars is more complex, and some may involve additional phenomenology, such as internal or very high core Faraday rotation.

scholarly journals The Optical Polarization of QSOs

1982 ◽  
Vol 97 ◽  
pp. 341-344
Author(s):  
Richard L. Moore
Keyword(s):  
Emission Lines ◽  
Optical Polarization ◽  
Bl Lac Objects ◽  
Strong Emission ◽  
Relativistic Beaming ◽  
Bl Lac ◽  
Polarization Studies

Recent optical polarization studies indicate that there are two distinct types of QSOs — “normal” QSOs with P ≲ 1%, and highly polarized QSOs (HPQs) with P > 3%. The HPQs are very similar to BL Lac objects, yet still share some properties of normal QSO's (e.g. strong emission lines). Our results generally support the relativistic beaming model for QSOs; however, certain key predictions of this model are not observed.

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