2016/07/29 by E. Aliu, S. Archambault, A. Archer +116
Physics and Astronomy · #Astronomy #Astrophysics #Astrophysics and Cosmic Phenomena #Blazar #Crab Nebula #Fermi Gamma-ray Space Telescope #Flare #Flux (metallurgy) #Gamma ray #Gamma-ray bursts and supernovae #Nebula #Physics #Radio Astronomy Observations and Technology #Stars #Wavelength #astro-ph.HE
paper · pdf · doi:10.1051/0004-6361/201628744
published as A&A 594, A76 (2016) · 13 pages, 10 figures. Accepted for publication in Astronomy and Astrophysics
openalex publication_date 2016/07/29 · arxiv created 2016/08/04 · openalex created_date 2016/08/23 · arxiv updated 2016/10/19 · openalex updated_date 2026/08/05
The very high energy (VHE; E> 100 GeV) blazar Markarian 501 was observed between April 17 and May 5 (MJD 54 938–54 956), 2009, as part of an extensive multi-wavelength campaign from radio to VHE. Strong VHE γ-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 × 10-11 ph cm-2 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°. This VHE flare showed a fast flux variation with an increase of a factor ~4 in 25 min, and a falling time of ~50 min. 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.