Related papers: Correlations between X-ray spectral parameters of …
Blazar flares have been suggested as ideal candidates for enhanced neutrino production. While the neutrino signal of $\gamma$-ray flares has been widely discussed, the neutrino yield of X-ray flares has received less attention. Here, we…
In the present paper, we have reported the result of simultaneous multi-wavelength observations of the TeV blazar Mrk 421 during February $-$ March 2003. In this period, we have observed Mrk 421 using Pachmarhi Array of \v{C}erenkov…
With currently available XMM-Newton EPIC pn observations spanned over about 3 years, we present a detailed spectral and temporal variability of the 0.2--10 keV X-ray emission from the X-ray bright BL Lac object PKS 2155-304. The spectral…
We present results from the first dedicated study in the time domain of the hard X-ray variability behavior of blazars on long timescales based on $\sim$13 years of continuous hard X-ray data in the 14-195 keV band. We use monthly-binned…
The blazar PKS0537-441 has been observed by Swift between the end of 2004 and November 2005. The BAT monitored it recurrently for a total of 2.7 Ms, and the XRT and UVOT pointed it on seven occasions for a total of 67 ks, making it one of…
We report on long-term multi-wavelength monitoring of blazar Mrk~421 from 2010 to 2011. The source exhibited extreme X-ray flares in 2010. Our research group performed optical photopolarimetric follow-up observations using the Kanata…
We present time-resolved spectral analysis of the steep decay segments of 29 bright X-ray flares of gamma-ray bursts (GRBs) observed with the Swift/X-ray telescope, and model their lightcurves and spectral index evolution behaviors with the…
We carried a detailed time and flux resolved X-ray spectral analysis of the high-synchrotron-peaked blazar Mrk\,421 using simultaneous LAXPC20 and SXT observations. The 100\,s binned LAXPC20 light curve obtained during 3--8 January 2017…
SGR~0501+4516 was discovered with the Swift satellite on 2008 August 22, after it emitted a series of very energetic bursts. Since then, the source was extensively monitored with Swift, the Rossi X-ray Timing Explorer (RXTE) and observed…
The X-ray spectrum of Mkn 478 is known to be dominated by a strong soft excess which can be described using relativistic blurred reflection. Using observations from {\it XMM-Newton}, {\it AstroSat} and {\it Swift}, we show that for the…
We present new ultraviolet photometry of the jet in M87 obtained from HST WFPC2 imaging. We combine these ultraviolet data with previously published photometry for the knots of the jet in radio, optical, and X-ray, and fit three theoretical…
Optical observations of a sample of 12 $\gamma$-ray bright blazars from four optical data archives, AAVSO, SMARTS, Catalina, and Steward Observatory, are compiled to create densely sampled light curves spanning more than a decade. As a part…
X-ray flares of gamma-ray bursts (GRBs) are usually observed in the soft X-ray range and the spectral coverage is limited. In this paper, we present an analysis of 32 GRB X-ray flares that are simultaneously observed by both BAT and XRT on…
We compare the rise and decay timescales of $\sim$200 long-term ($\sim$weeks-months) GeV and R-band outbursts and $\sim$25 short-term ($\sim$hr-day) GeV flares in a sample of 10 blazars using light curves from the Fermi-LAT and the…
Observations of gamma ray bursts (GRBs) with Swift produced the initially surprising result that many bursts have large X-ray flares superimposed on the underlying afterglow. The flares were sometimes intense, had rapid rise and decay…
Context. Blazar AO 0235+164, located at redshift z = 0.94, has undergone several sharp multi-spectral-range flaring episodes during the last decades. In particular, the episodes peaking in 2008 and 2015, that received extensive…
The bright X-ray selected BL Lacertae object PKS 2155-304 has been the target of two intense multiwavelength campaigns, in November 1991 and in May 1994. Although the spectral energy distributions at both epochs were quite similar, the…
We present the results from a study of the long-term optical spectral variations of BL Lacertae, using the long and well-sampled B and R-band light curves of the Whole Earth Blazar Telescope (WEBT) collaboration, binned on time intervals of…
The new results of the evolution of the synchrotron peak for Mrk 421 are mostly likely related to the particle acceleration process. In order to account for the above results, we present a model of blazar variability during the flare in…
We present an updated catalog of 113 X-ray flares detected by Swift in the ~33% of the X-ray afterglows of Gamma-Ray Bursts (GRB). 43 flares have a measured redshift. For the first time the analysis is performed in 4 different X-ray energy…