Fermi LAT Detection of GeV Gamma-Ray Emission from the Binary System PSRB1259-63

ATel #3085; A. A. Abdo (GMU, resident at NRL), D. Parent (GMU, resident at NRL), J. E. Grove (NRL) G. A. Caliandro (IEEC-CSIC) on behalf of the Fermi Large Area Telescope Collaboration; M. Roberts (Eureka Scientific), S. Johnston (ATNF), M. Chernyakova (DIAS)
on 22 Dec 2010; 21:45 UT
Credential Certification: A. A. Abdo (aous.abdo@nrl.navy.mil)

Tweet

We report on the detection of GeV gamma-ray emission spatially coincident with the binary system PSR B1259-63 with the Large Area Telescope (LAT), one of the two instruments on board the Fermi Gamma-ray Space Telescope.

Preliminary analysis of 32 days of Fermi-LAT data in the region around the system in the period 2010-11-17 to 2010-12-19 UTC gives a flux (E >100 MeV) of 1.2 +/- 0.6 x 10^-7 ph cm^- 2 s^- 1 and a photon index of 2.2 +/- 0.2. The detection significance is 5 sigma. This covers the time period from when the pulsar started crossing the Be star's disk at twice its opening angle (Chernyakova et al. MNRAS 367, 1201 2006) to the time of the periastron. In contrast, for the 32 day time period between 2010-08-09 and 2010-09-10 UTC in which the pulsar was far away from the Be star and its disk we place a 95% confidence upper limit of 0.5 x 10^-7 ph cm^-2 s^-1, and we note that no gamma-ray source at the location of PSR B1259-63 has previously been detected by the LAT on any timescale since LAT science operations began in Aug 2008 (Atel #2780 and Atel #3054). A systematic uncertainty of 30% should be added in quadrature to the statistical uncertainties listed here.

As part of the continued monitoring of this system in our multi-wavelength campaign, our radio and X-ray observations so far suggest the unpulsed radio flux from ATCA and X-ray flux from Swift is consistent with what was seen in previous periastron passages (Johnston et al. MNRAS 302, 277 1999, Chernyakova et al. MNRAS 397, 2123 2009).

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 strongly encourage multi-wavelength observations. For this source the Fermi LAT contact person is Aous Abdo (aous.abdo@nrl.navy.mil).

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.