Optical Short-Term Variability in the X-Ray-Selected BL Lac Object IE 0317+186 and the Radio-Selected BL Lac Object ON231
نویسندگان
چکیده
منابع مشابه
Unusual radio variability in the BL Lac object 0235 + 164
We present radio observations at three frequencies and contemporaneous optical monitoring of the peculiar BLLac object AO0235+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 pr...
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We discuss alternative interpretations of the differences in the Spectral Energy Distributions (SEDs) of BL Lacs found in complete Radio or X–ray surveys. A large body of observations in different bands suggests that the SEDs of BL Lac objects appearing in X–ray surveys differ from those appearing in radio surveys mainly in having a (synchrotron) spectral cut–off (or break) at much higher frequ...
متن کاملIntraday variability in x - ray selected BL
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 کاملExtraordinary Activity in the BL Lac Object OJ 287
We use a continuous wavelet transform to analyze more than two decades of data for the BL Lac object OJ 287 acquired as part of the UMRAO variability program. We find clear evidence for a persistent modulation of the total flux and polarization with period ∼ 1.66 years, and for another signal that dominates activity in the 1980s with period ∼ 1.12 years. The relationship between these two varia...
متن کاملSpectroscopic monitoring of the BL Lac object AO 0235 + 164 ⋆
Aims. Spectroscopic monitoring of BL Lac objects is a difficult task that nonetheless can provide important information on the different components of the active galactic nucleus. Methods. We performed optical spectroscopic monitoring of the BL Lac object AO 0235+164 (z = 0.94) with the VLT and TNG telescopes from Aug. 2003 to Dec. 2004, during an extended WEBT campaign. The flux of this source...
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ژورنال
عنوان ژورنال: Symposium - International Astronomical Union
سال: 1989
ISSN: 0074-1809
DOI: 10.1017/s0074180900140513