منابع مشابه
New Results from the Hrx Bl Lac Sample
We present results for the Hamburg BL Lac sample, based on data provided by the RASS-BSC. By fitting a single power law to the X-ray data we find, in a number of objects, an additional absorbing component to the galactic value of NH , which might be attributed to intrinsic absorption. A more probable cause seems however to be a curvature in the X-ray spectra in the sense that they are more curv...
متن کاملNew Extreme Synchrotron Bl Lac Objects
We report on the BeppoSAX observations of four “extreme” BL Lacs, selected to have high synchrotron peak frequencies. All have been detected also in the PDS band. For 1ES 0120+340, PKS 0548–322 and H 2356–309 the spectrum is well fitted by a convex broken powerlaw, thus locating the synchrotron peak around 1–4 keV. 1ES 1426+428 presents a flat energy spectral index (αx = 0.92) up to ∼100 keV, t...
متن کاملBl Lac Objects
SUMMARY: We present the radio detection of 18 BL Lac objects from our survey of over 575 deg 2 of sky. These 18 objects are located within 20 ′′ of the X-ray position, of which 11 have a measured red-shift. All candidates are radio emitters above ∼1 mJy and fall within the range of existing samples on the two colour, α ro vs α ox , diagram with a transitional population of three (3) evident. Tw...
متن کاملOn the Nature of BL Lac Objects
The BL Lacertae objects, or BL Lacs, have multi-wavelength continua dominated by non-thermal emission from a relativistic jet, and are characterised by a lack of optical emission lines. We find, through observations and modelling that the dominant factor in a source being called a BL Lac is the intrinsic lack of flux from the broad-line region – likely connected with a weak accretion disc – rat...
متن کاملTeV candidate BL Lac objects
The TeV emission of low power BL Lac objects has been established by the detection of an handful of them. The knowledge of the level of the TeV emission and its spectrum can shed light on the particle acceleration mechanisms, and it is especially important to assess the still uncertain level of the far infrared background radiation, which can absorb the TeV photons through photon–photon interac...
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ژورنال
عنوان ژورنال: International Astronomical Union Colloquium
سال: 2002
ISSN: 0252-9211
DOI: 10.1017/s0252921100030578