Very High Energy outburst of Markarian 501 in May 2009

Abstract

The very high energy (VHE; E $>$ 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54938--54956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE $\gamma$-ray activity was detected on May 1st with Whipple and VERITAS, when the flux (E $>$ 400 GeV) increased to 10 times the pre-flare baseline flux ($3.9\times 10^{-11}\mathrm{ph}\mathrm{c}{\mathrm{m}}^{-2}{\mathrm{s}}^{-1}$), reaching five times the flux of the Crab Nebula. This coincided with a decrease in the optical polarization and a rotation of the polarization angle by 15${}^{\circ }$. This VHE flare showed a fast flux variation with an increase of a factor $\sim$4 in 25 minutes, and a falling time of $\sim$50 minutes. We present the observations of the quiescent state previous to the flare and of the high state after the flare, focusing on the flux and spectral variability from Whipple, VERITAS, Fermi-LAT, RXTE, and Swift combined with optical and radio data.

13 pages, 10 figures. Accepted for publication in Astronomy and Astrophysics

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• H.E.S.S. detection of very-high-energy gamma-ray emission from the quasar PKS 0736+017
• The VHE SED modelling of Markarian 501 in 2009
• A two-zone photohadronic scenario for EHBL-like behavior of Mrk 501
• Long-term multi-band photometric monitoring of Mrk 501
• EBL effect on the observation of multi-TeV flaring of 2009 from Markarian 501
• Graviton-photon conversion in blazar jets as a probe of high-frequency gravitational waves
• X-Ray Spectral Variability of Thirteen TeV High Energy Peaked Blazars with XMM-Newton
• A Universal Energy Relation between synchrotron and Synchrotron Self-Compton radiation in GRBs and Blazars
• Prospects of additional contribution at Optical-NIR band of EBL in the light of VHE spectra
• VTSCat - The VERITAS Catalog of Gamma Ray Observations
• Temporary EHBL-like behavior of Markarian 501 during July 2014 VHE flaring