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1. A catalogue of BL Lacertae objects
ID:
ivo://CDS.VizieR/J/MNRAS/277/1477
Title:
A catalogue of BL Lacertae objects
Short Name:
J/MNRAS/277/1477
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a catalogue of 233 BL Lacertae objects compiled through an extensive bibliographic search updated to mid-1995. A large fraction of the sources listed in the catalogue belongs to well-defined samples and can be used for statistical purposes. A smaller fraction consists of miscellaneous (but confirmed) BL Lacs and of objects classified as BL Lac candidates. We discuss the selection criteria of the different samples, report the discovery of two previously unnoticed BL Lacs in the Palomar-Green survey, and comment on the possible association of some of the still unidentified high galactic latitude gamma-ray (EGRET, see Thompson et al., =1995ApJS..101..259T) sources with BL Lacs. Some statistical properties of the catalogue are also briefly discussed.
2. AGN jet kinematics
ID:
ivo://CDS.VizieR/J/AJ/130/1418
Title:
AGN jet kinematics
Short Name:
J/AJ/130/1418
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present total and polarized intensity images of 15 active galactic nuclei obtained with the Very Long Baseline Array at 7mm (43GHz) wavelength at 17 epochs from 1998 March to 2001 April. At some epochs the images are accompanied by nearly simultaneous polarization measurements at 3mm (86GHz) with the Berkeley-Illinois-Maryland Association (BIMA) array (Hat Creek, California), 1.35/0.85mm (230/350GHz) with the James Clerk Maxwell Telescope (JCMT; using SCUBA and its polarimeter, and at the Steward Observatory 1.5m telescope (Mount Lemmon, Arizona) with the Two-Holer Polarimeter/Photometer over an effective wavelength range of ~6000-7000{AA}. Here we analyze the 7mm images to define the properties of the jets of two radio galaxies, five BL Lac objects, and eight quasars on angular scales >~0.1mas. We determine the apparent velocities of 106 features in the jets.
3. A 3.5mm polarimetric survey of radio-loud AGNs
ID:
ivo://CDS.VizieR/J/ApJS/189/1
Title:
A 3.5mm polarimetric survey of radio-loud AGNs
Short Name:
J/ApJS/189/1
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present the results from the first large (>100 sources) 3.5mm polarimetric survey of radio-loud active galactic nuclei (AGNs). This wavelength is favorable within the radio-millimeter range for measuring the intrinsic linearly polarized emission from AGNs, since in general it is only marginally affected by Faraday rotation of the electric vector position angle and depolarization. The I, Q, U, and V Stokes parameter observations were performed with the XPOL polarimeter at the IRAM 30m Telescope on different observing epochs from 2005 July (when most of the measurements were made) to 2009 October. Our sample consists of 145 flat-radio-spectrum AGNs with declination >-30{deg} (J2000.0) and flux density >~1Jy at ~86GHz, as measured at the IRAM 30m Telescope from 1978 to 1994. This constraint on the radio spectrum causes our sample to be dominated by blazars, which allows us to conduct new statistical studies on this class of high-luminosity, relativistically beamed emitters. Over our entire source sample, the luminosity of the jets is anticorrelated with the degree of linear polarization. Consistent with previous findings claiming larger Doppler factors for brighter {gamma}-ray blazars, quasars listed in our sample, and in the Fermi Large Area Telescope Bright Source Catalog (LBAS, Abdo et al., 2009ApJ...700..597A), show larger luminosities than non-LBAS ones, but our data do not allow us to confirm the same for BL Lac objects. Our new data can be used to estimate the 3.5mm AGN contribution to measurements of the linear polarization of the cosmic microwave background, such as those performed by the Planck satellite.
4. An optical overview of blazars with LAMOST. I.
ID:
ivo://CDS.VizieR/J/AJ/161/196
Title:
An optical overview of blazars with LAMOST. I.
Short Name:
J/AJ/161/196
Date:
16 Mar 2022 11:51:00
Publisher:
CDS
Description:
The extragalactic {gamma}-rays sky observed by the Fermi Large Area Telescope (LAT) is dominated by blazars. In the fourth release of the Fermi LAT Point Source Catalog (4FGL) are sources showing a multifrequency behavior similar to that of blazars but lacking an optical spectroscopic confirmation of their nature, known as blazar candidates of uncertain type (BCUs). We aim at confirming the blazar nature of BCUs and test if new optical spectroscopic observations can reveal spectral features, allowing us to get a redshift estimate for known BL Lac objects. We also aim to search for and discover changing-look blazars (i.e., blazars that show a different classification at different epochs). We carry out an extensive search for optical spectra available in the Large Sky Area Multi-object Fibre Spectroscopic Telescope (LAMOST) Data Release 5 (DR5) archive. We select sources out of the 4FGL catalog, the list of targets from our follow-up spectroscopic campaign of unidentified or unassociated {gamma}-ray sources, and the multifrequency catalog of blazars: the Roma-BZCAT. We select a total of 392 spectra. We also compare some of the LAMOST spectra with those available in the literature. We classify 20 BCUs confirming their blazar-like nature. Then we obtain 15 new redshift estimates for known blazars. We discover 26 transitional (i.e., changing-look) blazars that changed their classification. Finally, we are able to confirm the blazar-like nature of six BL Lac candidates. All remaining sources analyzed agree with previous classifications. BL Lac objects are certainly the most elusive type of blazars in the {gamma}-ray extragalactic sky.
5. Bimodal radio variability in OVRO blazars
ID:
ivo://CDS.VizieR/J/MNRAS/467/4565
Title:
Bimodal radio variability in OVRO blazars
Short Name:
J/MNRAS/467/4565
Date:
21 Oct 2021
Publisher:
CDS
Description:
Blazars are known to show periods of quiescence followed by outbursts visible throughout the electromagnetic spectrum. We present a novel maximum likelihood approach to capturing this bimodal behavior by examining blazar radio variability in the flux-density domain. We separate quiescent and flaring components of a source's light curve by modeling its flux-density distribution as a series of "off" and "on" states. Our modeling allows us to extract information regarding the flaring ratio, duty cycle, and the modulation index in the "off"-state, in the "on"-state, as well as throughout the monitoring period of each blazar. We apply our method to a flux-density-limited subsample from the Owens Valley Radio observatory's 15 GHz blazar monitoring program, and explore differences in the variability characteristics between BL Lacs and FSRQs as well as between {gamma}-ray detected and non-detected sources. We find that: (1) BL Lacs are more variable and have relatively larger outbursts than the FSRQs; (2) unclassified blazar candidates in our sample show similar variability characteristics as the FSRQs; and (3) {gamma}-ray detected differ from the {gamma}-ray non-detected sources in all their variability properties, suggesting a link between the production of {gamma}-rays and the mechanism responsible for the radio variability. Finally, we fit distributions for blazar flaring ratios, duty cycles, and on- and off- modulation indices that can be used in population studies of variability-dependent blazar properties.
6. Blazar candidates among Fermi/LAT 3FGL catalog
ID:
ivo://CDS.VizieR/J/A+A/602/A86
Title:
Blazar candidates among Fermi/LAT 3FGL catalog
Short Name:
J/A+A/602/A86
Date:
21 Oct 2021
Publisher:
CDS
Description:
We present a study to search for, and characterise blazar candidates among the Fermi/LAT 3FGL catalogue using machine-learning classification methods. Classifiers are based on the exploitation of statistical differences imprinted in the 3FGL Fermi/LAT catalogue, such as variability and spectral shape, between different populations of sources.
7. Blazar candidates behind the Magellanic Clouds
ID:
ivo://CDS.VizieR/J/ApJ/867/131
Title:
Blazar candidates behind the Magellanic Clouds
Short Name:
J/ApJ/867/131
Date:
21 Oct 2021
Publisher:
CDS
Description:
We report the identification of blazar candidates behind the Magellanic Clouds. The objects were selected from the Magellanic Quasars Survey (MQS), which targeted the entire Large Magellanic Cloud (LMC) and 70% of the Small Magellanic Cloud (SMC). Among the 758 MQS quasars and 898 of the unidentified (featureless spectra) objects, we identified a sample of 44 blazar candidates, including 27 flat-spectrum radio quasars and 17 BL Lacertae objects, respectively. All the blazar candidates from our sample were identified with respect to their radio, optical, and midinfrared properties. The newly selected blazar candidates possess the long-term, multicolor photometric data from the Optical Gravitational Lensing Experiment, multicolor midinfrared observations, and archival radio data for one frequency at least. In addition, for nine of them, the radio polarization data are available. With such data, these objects can be used to study the physics behind the blazar variability detected in the optical and midinfrared bands, as a tool to investigate magnetic field geometry of the LMC and SMC, and as an exemplary sample of point-like sources most likely detectable in the {gamma}-ray range with the newly emerging Cherenkov Telescope Array.
8. Blazar counterparts for 3EG sources
ID:
ivo://CDS.VizieR/J/ApJ/609/564
Title:
Blazar counterparts for 3EG sources
Short Name:
J/ApJ/609/564
Date:
21 Oct 2021
Publisher:
CDS
Description:
Supplementing existing survey data with Very Large Array (VLA) observations, we have extended {gamma}-ray counterpart identifications down to decl.=-40{deg} using our "figure-of-merit" approach. We find blazar counterparts for 70% of EGRET sources above decl.=-40{deg} away from the Galaxy. Spectroscopic confirmation is in progress, and spectra for 24 sources are presented here. We find evidence that increased exposure in the bulge region allowed EGRET to detect relatively faint blazars; a clear excess of nonblazar objects in this region, however, argues for an additional (new) source class.
9. Blazar Radio and Optical Survey (BROS)
ID:
ivo://CDS.VizieR/J/ApJ/901/3
Title:
Blazar Radio and Optical Survey (BROS)
Short Name:
J/ApJ/901/3
Date:
21 Oct 2021
Publisher:
CDS
Description:
Utilizing the latest and the most sensitive radio and optical catalogs, we completed a new blazar candidate catalog, Blazar Radio and Optical Survey (BROS), which includes 88211 sources located at decl. {delta}>-40{deg} and outside the galactic plane (|b|>10{deg}). We list compact flat-spectrum radio sources of {alpha}>-0.6 ({alpha} is defined as F_{nu}_{prop.to}{nu}^{alpha}^) from 0.15GHz TGSS to 1.4GHz NVSS catalogs. We further identify optical counterparts of the selected sources by cross-matching with Pan-STARRS1 photometric data. Color-color and color-magnitude plots for the selected BROS sources clearly show two distinct populations, a "quasar-like" population consisting of both flat-spectrum radio quasars and BL Lac type objects. On the other hand, an "elliptical-like" population of mostly BL Lac type objects is buried in the elliptical galaxy. The latter population is also reported in previous catalogs, but the BROS catalog provided a new larger sample of this population, due to the lower radio flux threshold of our selection. Model calculations show that the "elliptical-like" population consists of elliptical galaxies located at redshift z<=0.5, which is also supported by the logN-logS distribution of the power-law index of 1.49+/-0.05. This BROS catalog is useful for identifying the electromagnetic counterparts of ultra-high-energy cosmic rays and PeV neutrinos recently detected by IceCube, as well as nearby BL Lac objects detectable by future high-sensitivity TeV telescopes, such as the Cherenkov Telescope Array.
10. Blazar sequence
ID:
ivo://CDS.VizieR/J/MNRAS/451/2750
Title:
Blazar sequence
Short Name:
J/MNRAS/451/2750
Date:
21 Oct 2021
Publisher:
CDS
Description:
Based on a large Fermi blazar sample, the blazar sequence (synchrotron peak frequency {nu}_peak_ versus synchrotron peak luminosity L_peak_) is revisited. It is found that there is significant anticorrelation between {nu}_peak_ and L_peak_ for blazars. However, after Doppler correction the anticorrelation disappears. The jet cavity power (P_jet_) is estimated from the extended radio luminosity so that it is free of beaming effects. We find that there are significant anticorrelations between P_jet_ and the beam-corrected {nu}_peak_' for both blazars and radio galaxies, which supports the blazar sequence and the unification of blazars and radio galaxies (an alternative relationship is the correlation between jet power and {gamma}-ray photon index).

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