Related papers: X-ray Flares from Markarian 501

We have examined 40 NuSTAR light curves (LCs) of five TeV emitting high synchrotron peaked blazars: 1ES 0229+200, Mrk 421, Mrk 501, 1ES 1959+650 and PKS 2155-304. Four of the blazars showed intraday variability in the NuSTAR energy range of…

High-resolution radio observations are ideal for constraining the value of physical parameters in the inner regions of active-galactic-nucleus jets and complement results on multiwavelength (MWL) observations. This study is part of a wider…

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…

Extremely High energy peaked BL Lac (EHBL) objects are a special class of blazars with peculiar observational properties at X-ray and $\gamma$--ray energies. The observations of these sources indicate hard X-ray and $\gamma$--ray spectra…

In 2012 Markarian 421 underwent the largest flare ever observed in this blazar at radio frequencies. In the present study, we start exploring this unique event and compare it to a less extreme event in 2013. We use 15 GHz radio data…

Strong X-ray flares from the blazar Mrk 421 were detected in 2010 January and February through the 7 month monitoring with the MAXI GSC. The maximum 2 -- 10 keV flux in the January and February flares was measured as 120 +- 10 mCrab and 164…

We present a preliminary analysis of new high resolution radio observations of the nearby TeV blazar Markarian 421 (z=0.031). This study is part of an ambitious multifrequency campaign, with observations in sub-mm (SMA), optical/IR (GASP),…

Most active galactic nuclei at the center of the nearby galaxies have super-massive black holes accreting at sub-Eddington rates through hot accretion flows or radiatively inefficient accretion flows, which efficiently produce jets. The…

Blazars are a subclass of AGN and flaring in multi-TeV gamma-ray seems to be the major activity in high energy blazars a subgrup of blazars. Flaring is also unpredictable and switches between quiescent and active states involving different…

Aims: The TeV BL Lac object Markarian 501 is a complex, core dominated radio source, with a one sided, twisting jet on parsec scales. In the present work, we attempt to extend our understanding of the source physics to regions of the radio…

We report the results obtained for the AGN Markarian 421 by model-fitting the data in the visibility plane, studing the proper motion of jet components, the light curve, and the spectral index of the jet features. We compare the radio data…

We are performing an unprecedentedly long and dense monitoring of the multi-frequency (radio to TeV) emission from the classical TeV blazars Mkn 421 and Mkn 501. These objects are among the brightest X-ray/TeV blazars in the sky and among…

We present the results of extensive modeling of the spectral energy distributions (SEDs) of the closest blazar (z=0.031) Markarian 421 (Mrk 421) during a giant outburst in February 2010. The source underwent rapid flux variations in both…

We conducted a daily monitoring campaign on Mrk 421 in 2003 and 2004 with the Whipple 10 m telescope and the large-area instruments aboard RXTE, simultaneously covering TeV and X-ray energies. Supporting observations at optical and radio…

The last years have seen a revolution in ground-based gamma-ray detectors. We can now detect the spectra of nearby TeV blazars like Mrk 421 and 501 out to approximately 20 TeV, and during the strongest flares, we can now follow fluctuations…

Blazars are highly variable sources over timescales that can be as low as minutes. This is the case of the High Energy Peaked BL Lac (HBL) objects showing strong variability in X-rays, which highly correlate with that of the TeV emission.…

BL Lacertae (BL Lac) is categorized as TeV blazar and considered as a possible source of astrophysical neutrinos. In 2020, the brightest X-ray flare ever detected from it. A detailed study can answer many puzzling questions related to…

We report on observations of Markarian 421 made with the Whipple 10m Cerenkov telescope and the RXTE satellite during a multi-wavelength campaign in December 2002 and January 2003, initiated by a Whipple target of opportunity. The…

In 1997, the BL Lac Object Mrk 501 entered a very active phase and was the brightest source in the sky at TeV energies, showing strong and frequent flaring. Using the data obtained with a high density air shower array that has been…

We study the multi-band variability and correlations of the TeV blazar Mrk 421 on year time scales, which can bring additional insight on the processes responsible for its broadband emission. We observed Mrk 421 in the very high energy…