Fermi/LAT and Swift/XRT observations of PSR B1259-63/LS 2883 over the recent periastron passage
ATel #6198; P. H. Thomas Tam and Albert K. H. Kong (National Tsing Hua University, Taiwan)
on 3 Jun 2014; 17:37 UT
Credential Certification: P.H.Thomas Tam (grbtom@gmail.com)
Subjects: X-ray, Gamma Ray, Binary, Neutron Star
We report on the Fermi/LAT and Swift/XRT observations of the binary system PSR B1259-63/LS 2883 over its recent periastron passage that occurred on May 4, 2014.
Analysis of the LAT data at a regular basis has been performed since April 1, 2014; no significant emission (i.e., above 5-sigma) has been seen. An analysis using data taken between April 10 and May 30 does not show significant emission above 100 MeV. We place a 90% c.l. upper limit on the 0.1-300 GeV photon flux at 4.2 x 10-8 ph cm-2 s-1 during this period.
GeV emission from the binary was first detected just before the last periastron passage on Dec 14, 2010, followed by flares starting from a month after the passage (Tam et al., 2011, ApJL, 736, L10; Abdo et al., 2011, ApJL, 736, L11).
Regular monitoring of Swift/XRT have been performed since April 20, 2014. While the recent X-ray light curve is similar to those seen in previous periastron passages, the peak after the passage that occurred on May 22, 2014 has a count rate of 1.0 ct/s (0.3-10 keV) - it represents the highest X-ray count rate ever seen from this binary. The derived energy flux of 6 x 10-11 erg cm-2 s-1 (0.3-10 keV) is a factor of 1.6 higher than that seen for the post-periastron peaks in the years 2007 and 2010 (which is ~3.7 x 10-11 erg cm-2 s-1; see, e.g., Abdo et al., 2011, ApJL, 736, L11).
We thank the Swift team for scheduling the Target of Opportunity (ToO) requests. We note that a Fermi ToO pointed observations of PSR B1259-63 are ongoing.