Fermi LAT detection of an outburst from the Galactic center region

ATel #3162; Vlasios Vasileiou (LUPM Montpellier), James Chiang (KIPAC/SLAC), Nicola Omodei (Stanford University), Frederic Piron (LUPM Montpellier), Giacomo Vianello (CIFS/SLAC), and Julie McEnery (NASA GSFC)
on 12 Feb 2011; 17:30 UT
Distributed as an Instant Email Notice Transients
Credential Certification: Julie McEnery (julie.mcenery@nasa.gov)

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The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope detected on 10 February 2011 16:18:02 UT an outburst from a position in the Galactic center region at:

(R.A., Dec) = (+266.69 deg, -28.98 deg) = (17 46 45.6, -28 58 48.0) (J2000) with statistical uncertainty of 0.36 deg (1 sigma).

The position is equivalent to (l, b) = (+0.09 deg, -0.23 deg).

This outburst was detected by our automated blind search for transients, and the measurements were refined by further dedicated analyses. The detected signal extends to GeV energies and lasted about ~20 seconds. Within that time interval, the LAT detected 17 events of the transient data class with an expected background of 11 events. Accounting for the energy and spatial distribution of the events, these data yield a detection significance of greater than 4 sigma. We caution that this is a weakly detected transient. Hence, the results reported here are preliminary.

Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. In consideration of the activity of this source we strongly encourage multi-wavelength observations. The Fermi LAT contact person for this source is Vlasios Vasileiou (vlasios.vasileiou@univ-montp2.fr).

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.