منابع مشابه
Broadband Spectra and Variability of BL Lacertae in 2000
We have organized an extensive multiwavelength campaign on BL Lacertae in the second half of 2000. Simultaneous or quasi-simultaneous observations were taken at radio frequencies, in the optical — carried out by the WEBT collaboration —, in X-rays — using BeppoSAX and RXTE —, and at VHE gamma-rays with the CAT and HEGRA Cherenkov telescope facilities. In this paper, we are presenting first resu...
متن کاملUnusual radio variability in the BL Lacertae object 0235 + 164
We present radio observations at three frequencies and contemporaneous optical monitoring of the peculiar BL Lac object AO 0235+164. During a three-week campaign with the VLA we observed intraday variability in this source and found a distinct peak which can be identified throughout the radio frequencies and tentatively connected to the R-band variations. This event is characterized by unusual ...
متن کاملIntraday variability in X-ray selected BL Lacertae objects
We present a study of the intraday variability behaviour of two samples of X-ray selected BL Lac objects, the EMSS and EXOSAT samples consisting of 22 and 11 sources, respectively. In both samples we were able to detect intraday variability in less than 40% of the sources only. The duty cycle (the fraction of time, when a BL Lac object is variable) in X-ray selected BL Lac objects is 0.4 or les...
متن کاملThe long-term optical spectral variability of BL Lacertae
Context. We present the results from a study of the long-term optical spectral variations of BL Lacertae, using the long and wellsampled B and R-band light curves of the Whole Earth Blazar Telescope (WEBT) collaboration, binned on time intervals of 1 day. Aims. To study the relation between the long-term spectral variations and the respective flux variations of the source. Methods. We use cross...
متن کاملModeling the Variability of the Bl Lacertae Object Pks 21552304
The bright X-ray–selected BL Lacertae object PKS 21552304 has been the target of two intense multiwavelength campaigns: in 1991 November and in 1994 May. Although the spectral energy distributions at both epochs were quite similar, the source exhibited two very distinct variability patterns that cannot be easily reconciled with homogeneous, one-zone jet models. During the first epoch the variab...
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ژورنال
عنوان ژورنال: Astronomy & Astrophysics
سال: 2009
ISSN: 0004-6361,1432-0746
DOI: 10.1051/0004-6361/200912303