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Swift/BAT spectral analysis of the Crab after September 2010 gamma-ray flare

ATEL # 2893; T. Sakamoto (GSFC/UMBC), S. D. Barthelmy (GSFC), W. H. Baumgartner (GSFC/UMBC), J. R. Cummings (GSFC/UMBC), E. E. Fenimore (LANL), N. Gehrels (GSFC), H. A. Krimm (GSFC/USRA), C. B. Markwardt (GSFC), D. M. Palmer (LANL), M. Stamatikos (OSU), J. Tueller (GSFC), T. N. Ukwatta (GWU)
on 30 Sep 2010; 21:33 UT
Password Certification: Takanori Sakamoto (

Subjects: X-ray, Neutron Stars, Pulsars

We report the Swift/BAT detailed analysis of the Crab data from September 2010 when a gamma-ray flare has been observed by AGILE (Atel#2855) and Fermi/LAT (Atel#2861). We found no significant variation in either the 15-150 keV flux and the photon index during this period. We collected the BAT survey data (Detector Plane Histograms) when the Crab was in the BAT field of view. We used the mask weighting technique to construct a spectrum of the Crab for each pointing. We have 84 spectra in total. A simple power-law model is used to extract the flux and the photon index of each observation. The spectral fit range is 14-150 keV. The mean energy flux in the 15-150 keV band before the gamma-ray flare (between 1-17 September) is 2.10e-8 erg/cm2/s. All the observed fluxes after the gamma-ray flare (18-27 September) are consistent within 5% from this mean flux value. Also, the observed photon indices of the post flare period are consistent within 5% from the their mean value of the pre-flare period of 2.16. We also looked closer around the actual gamma-ray flaring period between 18-22 September (Atel#2879) of the BAT data. There is no significant variation in either the flux and the photon index during this gamma-ray flaring period.

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