Fermi LAT detection of a GeV flare from MG1 J050533+0415

ATel #3573; D. Gasparrini (ASDC/INAF) on behalf of the Fermi Large Area Telescope Collaboration
on 20 Aug 2011; 17:37 UT
Credential Certification: Dario Gasparrini (dario.gasparrini@asdc.asi.it)

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The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed an increasing gamma-ray flux from a source positionally consistent with MG1 J050533+0415 (also known as BZB J0505+0415, GB6 J0505+0415,PMN J0505+0416 and RX J0505.5+0416).

MG1 J050533+0415 (RA:05h05m34.774s DEC:+04d15m54.62s, J2000, N. Jackson et al. 2007, MNRAS, 376, 371) is a BL Lac object associated with 2FGL J0505.4+0419 (M. Ackermann et al. 2011, submitted to ApJ, arXiv:1108.1420)

Preliminary analysis indicates that MG1 J050533+0415 on August 19, 2011, was in a high state with a daily gamma-ray flux (E > 100MeV) of (1.2+/-0.2)x10^-6 photons/cm^2/s(errors are statistical only), which represents an increase of a factor of about 120 with respect to the average source flux observed in the first two years of Fermi observations (A. Abdo et al. 2011, submitted to ApJ, arXiv:1108.1435). During the six-hour interval from 00:00:00 to 06:00:00 UTC on the same day, the source reached a gamma-ray flux (E > 100MeV) of (3.7+/-0.9)x10^-6 photons/cm^2/s (errors are statistical only).

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the ongoing activity of this source we encourage multi-wavelength observations. For MG1 J050533+0415 the Fermi LAT contact person is David Thompson (David.J.Thompson@nasa.gov).

The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.