Related papers: Radio Detection of 18 Rass BL Lac Objects

This paper presents a new sample of BL Lac objects selected from a deep (30 mJy) radio survey of flat spectrum radio sources (the CLASS blazar survey, henceforth CBS). The sample is one of the largest well defined samples in the low power…

We have searched the archived, pointed ROSAT Position Sensitive Proportional Counter data for blazars by correlating the WGACAT X-ray database with several publicly available radio catalogs, restricting our candidate list to serendipitous…

We present new radio data completing the imaging for a sample of 30 nearby (z < 0.2) BL Lac objects on parsec and kiloparsec scale. The sample is composed of both high and low luminosity sources and it is therefore an ideal test bed for…

Observations at millimetre wavelengths are presented for a representative sample of 22 X-ray-selected BL Lac objects (XBLs). This sample comprises 19 High-energy cutoff BL Lacs objects (HBLs), 1 Low-energy cutoff BL Lac object (LBL) and 2…

Context. Although Blazars are a small fraction of the overall AGN population they are expected to be the dominant population of extragalactic sources in the hard X-ray and gamma-ray bands and have been shown to be the largest contaminant of…

H1517+656 is an unusual source, even for a BL Lac object. It is one of the most luminous BL Lacs known, with extreme emission properties at radio, optical, and X-ray frequencies. Furthermore, in our WFPC2 snapshot survey we discovered a…

Polarization measurements are presented for 52 radio-loud QSOs and BL Lac objects. For 9 highly polarized (p >3%) AGN, these are the first published polarization measurements. Of these 9, 7 are highly-polarized QSOs (HPQs), one is a BL Lac…

In preparation for GLAST, we have compiled a sample of blazar candidates to increase the pool of well studied AGN from which GLAST counterparts will be drawn. Sources were selected with our Figure of Merit (FoM) ranking; thus, they have…

A complete sample of bright ROSAT sources with hard XRB-like spectra in the Galactic Plane (|b| < 15 deg.) has been tentatively identified with radio sources in the GB6/PMN/NVSS surveys, and subsequently observed with the Australia…

We present 6 ASCA and SAX observations of 4 intermediate BL Lac objects (1034+5727, 1055+5644, 1424+2401, 1741+1936). Their X-ray spectral properties and spectral energy distributions are compared to typical X-ray and radio selected BL…

Aims. We aim to determine the redshift (or stringent lower limits) of a number of bright BL Lacs objects. Methods. We secured medium resolution optical and near-infrared spectra of 4 bright BL Lac objects of unknown redshift using the…

The Herschel Astrophysical Terahertz Large Area Survey (H-ATLAS) provides an unprecedented opportunity to search for blazars at sub-mm wavelengths. We cross-matched the FIRST radio source catalogue with the 11655 sources brighter than 35…

Blazars are radio-loud Active Galactic Nuclei (AGN) whose jets have a very small angle to our line of sight. Observationally, the radio emission are mostly compact or a compact-core with a 1-sided jet. With 2.5$^{\prime\prime}$ resolution…

The existence of accreting supermassive black holes up to billions of solar masses at early cosmological epochs (in the context of this work, redshifts z>=6) requires very fast growth rates which is challenging to explain. The presence of a…

We investigate the properties of the three BL Lac objects, PKS 2201+044, 3C 371 and PKS 0521-365, that exhibit prominent optical jets. We present high resolution near-IR images of the jet of the first two, obtained with an innovative…

We report redshift measurements for 12 BL Lacertae objects from a program aimed at obtaining high signal to noise (up to ~ 500) optical spectroscopy of a mixed sample of objects. The new observations, gathered with the 8 m ESO Very Large…

Many properties of BL Lacs have become explicable in terms of the "relativistic beaming" hypothesis whereby BL Lacs are FR-1 radio galaxies viewed nearly along the jet axis. However, a possible problem with this model is that a transition…

We present the analysis of archival data from ROSAT and ASCA of a serendipitous source PKS 2316-423. According to its featureless non-thermal radio/optical continuum, the object has been assumed as a BL Lac candidate in the literature. It…

TeV-emitting BL Lac type blazars represent the extreme end of the blazar population. They are characterized by relatively weak jets and radiatively inefficient accretion disks. Particles accelerated in these jets experience fewer radiative…

We are carrying out a multi-purpose program of high signal to noise optical spectroscopy at medium resolution of 30 BL Lac objects. Here we report the detection of three new redshifts, and the discovery of three misclassified sources. The…