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Fermi LAT observations of the PSR B1259-63 region

ATEL # 2780; A. A. Abdo (NRL/NRC), A. B. Hill (LAGO), D. Parent (NRL/GMU), D. Hadasch (IEEC-CSIC); on behalf of the Fermi Large Area Telescope Collaboration
on 7 Aug 2010; 16:10 UT
Password Certification: Paul S. Ray (

Subjects: Gamma Ray, >GeV, Binaries, Transients
Referred to by ATEL #: 3046

Following the report of the detection of a transient gamma-ray source by AGILE from the region around PSR B1259-63 (ATEL # 2772) that occurred on 2010-08-02 06:40 UT to 2010-08-04 04:00 UT, we report on the non detection of a >100 MeV counterpart to this event with the Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope. Preliminary analysis indicates that no >100 MeV counterpart is observed in daily or 2-day integrations around 2010-08-02 06:40 UT to 2010-08-04 04:00 UT. Performing a maximum likelihood analysis and assuming a power-law spectrum with photon index = 2.2 for a source at the location of PSR B1259-63 we place a 95% confidence flux upper limit of 4E-7 ph cm-2 s-1 above 100 MeV. We get the same upper limit at the location of the AGILE source (RA=196.9, DEC=-63.7) which is 0.55 degrees away from the pulsar. Note that a persistent gamma-ray emission is not observed from PSR B1259-63 in Fermi LAT over any extended time period since science operations began in Aug 2008. Because Fermi operates in an all-sky scanning mode, regular gamma-ray monitoring of this source will continue. For this source the Fermi LAT contact person is Aous Abdo ( 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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