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Fermi LAT Detection of a longest GeV flare of the PSR B1259-63 Be-pulsar Binary System in 2017

ATel #10995; Xinbo He, P. H. Thomas Tam (SYSU)
on 23 Nov 2017; 05:51 UT
Credential Certification: P.H.Thomas Tam (grbtom@gmail.com)

Subjects: Gamma Ray, >GeV, Binary, Pulsar

Referred to by ATel #: 11028

Recently, we are monitoring the GeV emission from PSR B1259-63 with the data from the Fermi LAT, and previous results on the on-going GeV activities are reported in ATels #10775, #10818, #10924, #10925, #10972. Recently, we detected a new continued GeV flare which last about five days from 2017-11-17 01:00:00 UTC to 2017-11-22 01:00:00 UTC (i.e., from 56 to 60 days after the periastron in 2017, tp). This continued GeV flare is the longest detected GeV flare of PSR B1259-63 so far in 2017.

We used a power-law model to describe PSR B1259-63. We found that the TS values in the following one-day bins are above 22 (i.e., detection significance > 4.7 sigma) and the photon indices are between 2.3 and 3.2:

Time(t-tp; d)   index   photon flux (ph/s/cm^2)   TS value
56   2.83 +/- 0.29   1.49e-06 +/- 4.88e-07   30.35
57   2.36 +/- 0.11   3.06e-06 +/- 4.15e-07   174.65
58   2.73 +/- 0.15   3.88e-06 +/- 4.85e-07   162.17
59   3.19 +/- 0.35   1.99e-06 +/- 4.85e-07   40.84
60   3.03 +/- 0.37   1.28e-06 +/- 4.41e-07   22.12

PSR B1259-63 was detected with continued >100 MeV flares starting about 30 days after the periastrons in 2011 and 2014.

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.