منابع مشابه
Bl 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 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...
متن کاملIntermediate Scale Structures in BL Lac objects
Abstract. The parsec-scale total intensity structures of BL Lac objects share many characteristics with quasars: e.g. well-collimated jets and superluminal motion. However, the jets of BL Lac objects appear to fade much more quickly than those in quasars and on VLA scales many BL Lacs have structures comparable to those of low luminosity (FR I) radio galaxies, in which kpc-scale flow speeds are...
متن کاملVariable 21 cm absorption at z = 0 . 3127
We report multi-epoch GMRT HI observations of the z = 0.3127 damped absorber towards the quasar PKS 1127-145 , which reveal variability in both the absorption profile and the flux of the background source, over a timescale of a few days. The observed variations cannot be explained by simple inter-stellar scintillation (ISS) models where there are only one or two scintillating components and all...
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...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1972
ISSN: 0074-1809
DOI: 10.1017/s0074180900005696