Flaring activity from PSR B1259-63

ATel #6204; D. Malyshev, A. Neronov (ISDC - University of Geneva, CH), M. Chernyakova (DCU, Ireland)
on 6 Jun 2014; 10:06 UT
Credential Certification: Carlo Ferrigno (Carlo.Ferrigno@unige.ch)

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We report on the flaring activity from the binary system PSR B1259-63 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope.

The binary system PSR B1259-63 is a radio pulsar in a highly eccentric orbit (P=3.4yrs) around the massive main sequence star LS 2883. In 2011 FERMI/LAT observed (ATel #3115) a puzzling sharp increase of the flux one month after periastron passage. The flux has increased by factor of 14 in comparison with the one reported during the periastron passage. There were no signatures of the variability in radio, X-rays and TeV energy bands at the time of GeV flare.

The current periastron passage of PSR B1259-63 occurred on May 4, 2014. FERMI/LAT and SWIFT/XRT system observations over periastron passage are described in ATel #6198. If recurrent from orbit to orbit, the onset of the flaring activity for the current periastron passage was expected around June 4, 2014.

We performed binned analysis of 20x20 degrees region around PSR B1259-63 position taking into account all sources from 2FGL catalog (assuming power law spectra with free normalizations and indexes fixed to catalog values) and standard galactic and extragalactic backgrounds.

The preliminary analysis of ~2.3 days of the FERMI/LAT data taken from 2014-06-03 13:19:26 to 2014-06-05 20:49:37 UTC (FERMI MET 423494369 to 423694177) revealed increase of the flux from position consistent with PSR B1259-63. The detected flux (100MeV -300GeV) was 1.2±0.3 10^-6 ph/cm²/s assuming power law index 2.86, observed during the previous flare. The source was detected with test-statistical value TS=32 (~5 sigma detection significance). The TS further increases up to TS=55 (7 sigma significance) for a free power law index (the best fit value is 4.5±1.6).

Our analysis confirms the recurrent nature of the flaring activity of the source. The on-going flare has started exactly at the same orbital phase as the flare of the previous periastron passage. The flux level of the on-going flare is also comparable to that of the previous flare (ATel #3115).

We encourage followup multi-wavelength observations of PSR B1259-63, which should help to clarify the nature of its puzzling post-periastron flaring activity.

We acknowledge the use of public data from the FERMI/LAT data archive.