Multiwavelength study of the TeV blazar Mrk 421 during a giant flare

Shukla, Amit; Chitnis, V. R.; Vishwanath, P. R.; Acharya, B. S.; Anupama, G. C.; Bhattacharjee, Pooja; Britto, R. J.; Prabhu, T. P.; Saha, L.; Singh, B. B.

doi:10.1051/0004-6361/201118569

Cited by 53 publications

(64 citation statements)

References 38 publications

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“…The obtained parameters and chi squares ( all 2 c /ndf) are summarized in Table 6. The Doppler factor δ, ranging from 10 to 41, is similar to the ones found in previous investigations (Abdo et al 2011;Bartoli et al 2011a;Shukla et al 2012;Zhang et al 2012). The values of the magnetic field, B 0.1 G, are almost constant within a factor 2.…”

Section: The Ssc Model For Mrk 421supporting

confidence: 86%

“…The flux above 1 TeV is 2.7 I crab . HAGAR also observed Mrk 421 every night during F2 (Shukla et al 2012). The peak flux on February 17 (MJD = 55244) is about 7 I crab .…”

Section: Cherenkov Detectors Vhe γ-Ray Datamentioning

confidence: 83%

“…Therefore, the radio and UV data points were removed from the SSC model fitting. This choice is different from other authors, e.g., Abdo et al (2011) and Shukla et al (2012), who included them when fitting the SED. Finally, the SSC model generally underpredicts the UV and radio emissions.…”

Section: Discussionmentioning

confidence: 97%

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4.5 Years of Multi-Wavelength Observations of MRK 421 During the Argo-Ybj and Fermi Common Operation Time

Bartoli

Bernardini

et al. 2016

ApJS

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We report on the extensive multi-wavelength observations of the blazar Markarian 421 (Mrk 421) covering radio to γ-rays, during the 4.5 year period of ARGO-YBJ and Fermi common operation time, from 2008 August to 2013 February. These long-term observations, extending over an energy range of 18 orders of magnitude, provide a unique chance to study the variable emission of Mrk 421. In particular, due to the ARGO-YBJ and Fermi data, the entireenergy range from 100 MeV to 10 TeV is covered without any gap. In the observation period, Mrk 421 showed both low-and high-activity states at all wavebands. The correlations among flux variations in different wavebands were analyzed. The X-ray flux is clearly correlated with the TeV γ-ray flux, while the GeV γ-rays only show a partial correlation with the TeV γ-rays. Radio and UV fluxes seem to be weakly or not correlated with the X-ray and γ-ray fluxes. Seven large flares, including five X-ray flares and two GeV γ-ray flares with variable durations (3-58 days), and one X-ray outburst phase were identified and used to investigate the variation of the spectral energy distribution with respect to a relative quiescent phase. During the outburst phase and the seven flaring episodes, the peak energy in X-rays is observed to increase from sub-keV to a few keV. The TeV γ-ray flux increases up to 0.9-7.2 times the flux of the Crab Nebula. The behavior of GeV γ-rays is found to vary depending on the flare, a feature that leads us to classify flares into three groups according to the GeV flux variation. Finally, the one-zone synchrotron self-Compton model was adopted to describe the emission spectra. Two out of three groups can be satisfactorily described using injected electrons with a power-law spectral index around 2.2, as expected from relativistic diffuse shock acceleration, whereas the remaining group requires a harder injected spectrum. The underlying physical mechanisms responsible for different groups may be related to the acceleration process or to the environment properties.

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Section: The Ssc Model For Mrk 421supporting

confidence: 86%

“…The flux above 1 TeV is 2.7 I crab . HAGAR also observed Mrk 421 every night during F2 (Shukla et al 2012). The peak flux on February 17 (MJD = 55244) is about 7 I crab .…”

Section: Cherenkov Detectors Vhe γ-Ray Datamentioning

confidence: 83%

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4.5 Years of Multi-Wavelength Observations of MRK 421 During the Argo-Ybj and Fermi Common Operation Time

Bartoli

Bernardini

et al. 2016

ApJS

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“…Mrk 421 was observed at one of its brightest flaring episodes during February 2010 at energies above 250 GeV showing an enhancement in the flux level, with a maximum flux of ~7 Crab units detected on February 17, 2010. Spectral energy distributions during this flaring episode were constructed using data available at different energies including HAGAR to infer that the flaring occurred due to a passing shock in the jet (Shukla et al, 2012). Mkn 501 was found in moderately high state in 2010-11 reaching a peak activity in May 2011 (Shukla et al, 2014).…”

Section: Gamma Ray Astronomymentioning

confidence: 99%

Indian Astronomical Observatory, Leh-Hanle

Prabhu¹

2014

Proceedings of the Indian National Science Academy

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“…This blazar is a HBL with the synchrotron spectrum peaking in the X-ray regime. It is highly variable on all timescales and across all wavelengths from radio to TeVs, and has been studied comprehensively during its various flaring episodes by several authors (Aleksić et al 2012(Aleksić et al , 2010Acciari et al 2009;Shukla et al 2012;Isobe et al 2010;Krawczynski et al 2001;Ushio et al 2009;Tramacere et al 2009;Horan et al 2009;Lichti et al 2008;Fossati et al 2008;Albert et al 2007;Brinkmann et al 2003;Sinha et al 2015;Paliya et al 2015;Donnarumma et al 2009). Abdo et al (2011) studied the quiescent state emission from this source with the best-sampled SED to date.…”

Section: Introductionmentioning

confidence: 99%

Long-term study of Mkn 421 with the HAGAR Array of Telescopes

Sinha

Shukla

Saha

et al. 2016

A&A

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Context. The HAGAR Telescope Array at Hanle, Ladakh has been regularly monitoring the nearby blazar Mkn 421 for the past seven years. Aims. Blazars show flux variability in all timescales across the electromagnetic spectrum. While there is abundant literature characterizing the short-term flares from different blazars, comparatively little work has been carried out to study the long-term variability. We aim to study the long-term temporal and spectral variability in the radiation from Mkn 421 during 2009−2015. Methods. We quantify the variability and lognormality from the radio to very high-energy (VHE) bands, and compute the correlations between various wavebands using the z-transformed discrete correlation function. We construct the spectral energy distribution (SED) contemporaneous with HAGAR observation seasons and fit this SED with a one-zone synchrotron self-Compton model to study the spectral variability. Results. The flux is found to be highly variable across all timescales. The variability is energy dependant and is maximum in the X-ray and VHE bands. A strong correlation is found between the Fermi-LAT (gamma) and radio bands and between Fermi-LAT and optical, but no correlation is found between Fermi-LAT and X-ray. Lognormality in the flux distribution is clearly detected. This is the third blazar, following BL Lac and PKS 2155+304 to show this behaviour. The SED can be well fit by a one-zone SSC model, and variations in the flux states can be attributed mainly to changes in the particle distribution. A strong correlation is seen between the break energy γ b of the particle spectrum and the total bolometric luminosity.

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Multiwavelength study of the TeV blazar Mrk 421 during a giant flare

Cited by 53 publications

References 38 publications

4.5 Years of Multi-Wavelength Observations of MRK 421 During the Argo-Ybj and Fermi Common Operation Time

4.5 Years of Multi-Wavelength Observations of MRK 421 During the Argo-Ybj and Fermi Common Operation Time

Indian Astronomical Observatory, Leh-Hanle

Long-term study of Mkn 421 with the HAGAR Array of Telescopes

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