Related papers: FACT -- Multi-wavelength analysis of more than 30 …
We present an extensive study of 72 archival Chandra light curves of the high-frequency-peaked type blazar Mrk 421, the first strong extragalactic object to be detected at TeV energies. Between 2000 and 2015 Mrk 421 often displayed intraday…
Markarian 421 (Mrk 421) is one the brightest and closest (z=0.031) blazars known (de Vaucouleurs et al 1991). It is also one of the fastest varying TeV $\gamma$-ray sources, with a flaring activity on time scales as short as tens of…
Context: The blazar Markarian 421 is one of the brightest TeV gamma-ray sources of the northern sky. From December 2007 until June 2008 it was intensively observed in the very high energy (VHE, E > 100 GeV) band by the single-dish Major…
Blazars are known for their variability on a wide range of timescales at all wavelengths. Most studies of TeV gamma-ray blazars focus on short timescales, especially during flares. With a decade of observations from the Fermi-LAT and…
Understanding the high-energy emission processes and variability patterns are two of the most challenging research problems associated with relativistic jets. In particular, the long-term (months-to-years) flux variability at very high…
This paper presents the results of a detailed timing and spectral analysis of the TeV-detected blazar 1ES 1218+304, focused on the observations performed with the different instruments onboard the Neil Gehrels Swift Observatory in the…
The radiation mechanism of very high energy $\gamma$-ray emission from blazars and crucial parameters like magnetic field, and size of the emitting region are not well understood yet. To understand the above mentioned properties of blazars,…
We report on the detection of excess hard X-ray emission from the TeV BL Lac object Mrk421 during the historical low-flux state of the source in January 2013. NuSTAR observations were conducted four times between MJD56294 and MJD56312 with…
The blazar Markarian 421 (Mrk 421) is one of the brightest sources in the extragalactic X-ray/TeV sky. It is also one of the fastest varying TeV $\gamma$-ray sources, showing flaring activity on time scales as short as tens of minutes. To…
The GeV observations by Fermi-LAT give us the opportunity to characterize the high-energy emission (100 MeV - 300 GeV) variability properties of the BL Lac object S5 0716+714. In this study, we performed flux and spectral analysis of more…
Context. The radio galaxy IC 310 has recently been identified as a gamma-ray emitter based on observations at GeV energies with Fermi-LAT and at very high energies (VHE, E>100GeV) with the MAGIC telescopes. Originally classified as a…
Blazars are extremely variable objects emitting radiation across the electromagnetic spectrum and showing variability on time scales from minutes to years. For the understanding of the emission mechanisms, simultaneous multi-wavelength…
The TACTIC $\gamma$-ray telescope has observed Mrk 421 on 66 clear nights from Dec. 07, 2005 to Apr. 30, 2006, totalling $\sim$ 202 hours of on-source observations. Here, we report the detection of flaring activity from the source at $\geq$…
In 2008 the blazar Markarian 421 entered a very active phase and was one of the brightest sources in the sky at TeV energies, showing frequent flaring episodes. Using the data of ARGO-YBJ, a full coverage air shower detector located at…
The blazar Mrk 421 is one of the closest, brightest and fastest varying source in the extragalactic X-ray/TeV sky. In the last years, many multi-wavelength campaigns have been carried out to study the correlation between the very high…
Various attempts have been made in the literature at describing the origin and the physical mechanisms behind flaring events in blazars with radiative emission models, but detailed properties of multi-wavelength (MWL) light curves still…
Mkn 421 was repeatedly observed with BeppoSAX in 1997-1998. This is the first of two papers where we present the results of a thorough temporal and spectral analysis of all the data available to us, focusing in particular on the flare of…
Observations of fast TeV $\gamma$-ray flares from blazars reveal the extreme compactness of emitting regions in blazar jets. Combined with very-long-baseline radio interferometry measurements, they probe the structure and emission mechanism…
We investigate the origin of high-energy emission in blazars within the context of the leptohadronic one-zone model. We find that $\gamma$-ray emission can be attributed to synchrotron radiation either from protons or from secondary leptons…
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…