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Fermi LAT observations of gamma-ray activity from the binary system PSR B1259-63

ATel #3111; A. K.H. Kong, R. H.H. Huang, P. H.T. Tam (NTHU, Taiwan), C. Y. Hui (Chungnam, Korea)
on 17 Jan 2011; 07:14 UT
Credential Certification: Albert Kong (akong@phys.nthu.edu.tw)

Subjects: Binary, Transient, Pulsar

Referred to by ATel #: 6216

We report on the recent gamma-ray activity of the binary system PSR B1259-63 by the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope. The source was detected by the LAT when the pulsar crossed the disk of the Be star in mid-Nov (Tam et al. ATel #3046; Abdo et al. ATel #3085). After the periastron in mid-Dec, the gamma-ray emission has decreased significantly. By using the LAT data taking between 2010-12-22 and 2011-01-14 UT, the source was not detected with a likelihood test statistic (TS) of 4. We also examined the data between 2011-01-01 and 2011-01-14, the TS value is less than 1.

When the pulsar crossed the disk second time in mid-Jan after the periastron, we expect to see another gamma-ray flaring assuming the gamma-rays come from the interaction between the disk and the pulsar. Using the LAT data taking between 2011-01-14 and 2011-01-16, the gamma-ray flux of the region around PSR B1259-63 has increased significantly. The TS value of the source is about 39, corresponding to a detection significance of 6 sigma. The source spectrum can be described by a power-law model with a photon index of 3.6+/-0.4. The 200 MeV - 100 GeV flux is (4.8+/-0.9)e-7 ph/s/cm^2.

Multiwavelength observations of the source are strongly encouraged.