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GCN Circular 13859

GRB 121011A: Fermi-LAT detection of a burst
2012-10-12T02:13:58Z (12 years ago)
Judith Racusin at GSFC <>
M. Ohno (Hiroshima U.), G. Vianello (Stanford), J. L. Racusin (NASA/GSFC) and E. Sonbas (Adiyaman Univ.), report on behalf of the Fermi-LAT team:

The Fermi Large Area Telescope (LAT) detected emission from GRB 121011A, also detected by Swift (Racusin et al. GCN 13845) and GBM (trigger 371646928/121011469) at approximately 11:15:25 UT on October 11, 2012.

The burst location was inside the LAT field of view at an angle of ~56 degrees to the LAT boresight, and had a zenith angle of 86 degrees. No significant excess is seen using standard analysis procedures.

Using the non-standard LAT Low Energy (LLE) data selection, over 100 counts above background were detected within a 20 s interval coinciding with the time of the GBM emission, with a significance of 4 sigma. This data selection has insufficient spatial resolution to provide a reliable LAT localization. This detection is due to low energy gamma-rays (below 100 MeV). Indeed, no events were observed above 100 MeV using the standard analysis classes.

A GBM circular on GRB 121011A is forthcoming.

The Fermi LAT point of contact for this burst is Eda Sonbas (edasonbas AT

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.
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