Related papers: Temporal variability and estimation of jet paramet…
In this work, I have presented a multi-frequency variability and correlation study of the blazar Ton 599, which was observed first time in flaring state at the end of 2017. Data from \textit{Fermi}-LAT, Swift-XRT/UVOT, Steward Observatory,…
Blazars are known to emit exceptionally variable non-thermal emission over the wide range (from radio to $\gamma$-rays) of electromagnetic spectrum. We present here the results of our $\gamma$-ray flux and spectral variability study of the…
During the last 40-50 years, the TeV blazar Ton 599 has systematically experienced major outbursts detected in a wide wavelength range from radio to $\gamma$-rays. In this work, we present an analysis of Ton 599 quasi-periodic variability…
In this work, we provide a detailed analysis of the broadband temporal and spectral properties of the blazar Ton\,599 by using the observations from \emph{Fermi}-LAT and \emph{Swift}-XRT/UVOT telescopes, during its brightest $\gamma$-ray…
The correlation between optical and $\gamma$-ray flux variations in blazars reveals a complex behaviour. In this study, we present our analysis of the connection between changes in optical and $\gamma$-ray emissions in the blazar Ton 599…
In this work, we study the short term flaring activity from the high synchrotron peaked blazar Mrk 501 detected by the FACT and H.E.S.S. telescopes in the energy range 2-20 TeV during June 23-24, 2014 (MJD 56831.86-56831.94). We revisit…
We report results from a multi-wavelength monitoring campaign on Mrk 421 over the period of 2003-2004. The source was observed simultaneously at TeV and X-ray energies, with supporting observations frequently carried out at optical and…
The blazar Mrk 501 (z=0.034) was observed at very-high-energy (VHE, $E\gtrsim 100$~GeV) gamma-ray wavelengths during a bright flare on the night of 2014 June 23-24 (MJD 56832) with the H.E.S.S. phase-II array of Cherenkov telescopes. Data…
We investigate the peculiar properties of a large TeV gamma-ray flare from Mrk~501 detected during the 2009 multiwavelength campaign. We identify the counterpart of the flare in the Fermi/LAT telescope data and study its spectral and timing…
Context: The nearby (z=0.031) TeV blazar Mrk421 was reported to be in a high state of flux activity since November, 2009. Aims: To investigate possible changes in the physical parameters of Mrk421 during its high state of activity using…
A major flaring state of the BL Lac object Mrk 501 was observed by the High Energy Stereoscopic System (H.E.S.S.) in June, 2014. Flux levels higher than one Crab unit were recorded and rapid variability at very high energies ($\sim$2-20…
The highest-energy blazars exhibit non-thermal radiation extending beyond 1 TeV with high luminosities and strong variabilities, indicating extreme particle acceleration in their relativistic jets. The gamma-ray spectra of blazars contain…
Radio-to-TeV observations of the bright nearby (z=0.034) blazar Markarian 501 (Mrk 501), performed from December 2012 to April 2018, are used to study the emission mechanisms in its relativistic jet. We examined the multi-wavelength…
Combined with very-long-baseline interferometry measurements, the observations of fast TeV gamma-ray flares probe the structure and emission mechanism of blazar jets. However, only a handful of such flares have been detected to date, and…
The BL Lacertae object VER J0521+211 underwent a notable flaring episode in February 2020. A short-term monitoring campaign, led by the MAGIC (Major Atmospheric Gamma Imaging Cherenkov) collaboration, covering a wide energy range from radio…
The gamma-ray emission above 250 GeV from the BL Lac object Markarian 421 was observed by the CAT Cherenkov imaging telescope between December, 1996, and June, 2000. In 1998, the source produced a series of small flares, making it the…
The TeV-emitting BL Lac object Mkn 421 was observed with very long baseline interferometry (VLBI) at three closely-spaced epochs one-month apart in March-April 1998. The source was also monitored at very-high gamma-ray energies (TeV…
Blazars are variable emitters across all wavelengths over a wide range of timescales, from months down to minutes. It is therefore essential to observe blazars simultaneously at different wavelengths, especially in the X-ray and gamma-ray…
The TeV BL Lac object Markarian 501 has been the subject of a 4.5 month multi-instrument campaign conducted in 2009, which provided an excellent temporal and energy coverage from radio to very high energy gamma rays (>100 GeV, VHE). During…
We present exactly simultaneous X-ray and TeV monitoring with {\it RXTE} and HEGRA of the TeV blazar Mrk 501 during 15 days in 1998 June. After an initial period of very low flux at both wavelengths, the source underwent a remarkable flare…