Related papers: Patterns of variability in gamma-ray blazars
We present a multiwavelength study of the flat-spectrum radio quasar CTA 102 during 2013-2017. We use radio-to-optical data obtained by the Whole Earth Blazar Telescope, 15 GHz data from the Owens Valley Radio Observatory, 91 and 103 GHz…
I present a systematic study of gamma-ray flares in blazars. For this purpose, I propose a very simple and practical definition of a flare as a period of time, associated with a given flux peak, during which the flux is above half of the…
Due to its peculiar and highly variable nature, the blazar 3C 454.3 has been extensively monitored by the WEBT team. Here, we present for the first time these long-term optical flux and color variability results using data acquired in B, V,…
We have observed four low-luminosity active galactic nuclei classified as Type 1 LINERs with the X-ray Telescope (XRT) and the UltraViolet-Optical Telescope (UVOT) onboard Swift, in an attempt to clarify the main powering mechanism of this…
We obtained ultraviolet and optical spectra for 9 M~dwarfs across a range of rotation periods to determine whether they showed stochastic intrinsic variability distinguishable from flares. The ultraviolet spectra were observed during the…
During a period of strong $\gamma$-ray flaring activity from BL Lacertae, we organized Swift, Neutron star Interior Composition Explorer (NICER), and Nuclear Spectroscopic Telescope Array (NuSTAR) follow-up observations. The source has been…
Rapid intranight variability of continuum and polarization in blazars is a very useful tool to probe the beaming of a relativistic jet and the associated population of the relativistic particles. Such intranight variability in the…
Context. We present the light curves of six BL Lac objects, PKS 0537-441, PKS 0735+17, OJ 287, PKS 2005-489, PKS 2155-304, W Comae, and of the flat spectrum radio quasar PKS 1510-089, as a part of a photometric monitoring program in the…
We have presented a multiwavelength temporal and spectral study of the Blazar PKS 0346-27 for the period 2019 January-2021 December (MJD 58484-59575) using data from Fermi-LAT (gamma-rays), Swift-XRT (X-rays) and Swift-UVOT (ultra-violet…
The optical polarization plane of some blazars occasionally exhibits smooth hundred degree long rotations. Multiple theoretical models have been proposed to explain the nature of such events. A deterministic origin of these rotations,…
In an optical monitoring program to characterize the variability properties of blazar, we observed 10 sources from the Roma-BZCAT catalogue for 26 nights in V and R bands during October 2014 to June 2015 with two telescopes located in…
We present the results of a temporal and spectral study of the BL Lacertae object OJ 287 in optical, UV, and X-ray bands with observations performed by Swift satellite during September 2019--March 2020. In this period, the source showed…
A new procedure for smoothing a gamma-ray burst (GRB) lightcurve and calculating its variability is presented. Applying the procedure to a sample of 25 long GRBs, we have obtained a very tight correlation between the variability and the…
We study a sample of 30 high-redshift blazars ($z>2.5$) by means of spectra and the radiation mechanism with Fermi Large Area Telescope $\gamma$-ray observations spanning 15 years. Three models -- the power law, power law with an…
By studying the variability of blazars across the electromagnetic spectrum, it is possible to resolve the underlying processes responsible for rapid flux increases, so-called flares. We report on an extremely bright X-ray flare in the…
We compare the variability properties of very high energy gamma-ray emitting BL Lac objects in the optical and radio bands. We use the variability information to distinguish multiple emission components in the jet, to be used as a guidance…
The variability of the high-frequency peaked BL Lac object PKS 2155-304 is studied using almost 10 years of optical, X-ray and gamma-rays data. Publicly available data have been gathered and analyzed with the aim to characterize the…
In this presentation, we report the results of intraday variability in the optical (BVRI bands) and hard X-ray band (3-79 keV) in a number of blazars. In the optical microvariability studies of the blazars S5 0716+714 and BL Lac, we…
We have observed with ROSAT six blazars from the sample of 31 polarized objects constructed by Impey and Tapia (1988). Results of the spectral analysis in the ROSAT band of three objects, PKS 0301-243, PKS 1055+018 and PG 1424+240 are…
We present the results of our monitoring program to study the long-term variability of the Halpha line in high-mass X-ray binaries. We have carried out the most complete optical spectroscopic study of the global properties of high-mass…