BeppoSAX/PDS detection of Swift J1816.7-1613
Orlandini M. and Frontera F. (INAF/IASF Bologna)
Following the discovery of galactic X-ray transient Swift J1816.7-1613 (Krimm et al. ATel #1456) and the accurate localization by Chandra (Halpern et al. ATel #1457), we performed a search of this source in our BeppoSAX PDS data archive. We find that on 1998 September 29 the Chandra source position was within the field of view (1.3 deg FWHM) of one of the offset positions (+3.5 deg) of the PDS rocking collimators. The source was observed for 66 ksec. A significant signal of 0.303 +/- 0.046 Cts/s (6.5 sigma) in 15-30 keV and of 0.320 +/- 0.065 Cts/s (4.9 sigma) in 15-50 keV was observed. These excesses were determined by subtracting the background level measured in correspondence of the other offset position (-3.5 deg). Both directions corresponding to these positions lie on the galactic plane, with a contribution from the galactic ridge that we have evaluated to be negligible in the above energy bands. The energy spectrum is quite soft. When fit with a power law, the photon index is 6.0 +/- 1.0 (for comparison the galactic ridge spectrum has a photon index of about 1.8 (Valinia and Marshall 1998. Apj 505, 134)). Correcting for the triangular PDS angular response (Frontera et al 2007, ApJ 666, 86), the following source energy fluxes are derived: (3.6 +/- 0.5)E-11 cgs in 15-30 keV and (3.8 +/- 0.8)E-11 cgs in 15-50 keV, corresponding to 4.5 and 2.9 mCrab, respectively.
x-ray,binary,neutron star,pulsar,star,transient