TITLE: GCN CIRCULAR NUMBER: 10167 SUBJECT: GRB091111: Swift XRT refined analysis DATE: 09/11/13 14:19:06 GMT FROM: Vanessa Mangano at INAF-IASFPA V. Mangano, B. Sbarufatti (INAF-IASF PA), H. A. Krimm (CRESST/GSFC/USRA) and D. M. Palmer (LANL) report on behalf of the Swift-XRT team: The INTEGRAL burst GRB091111 (Gotz et al. GCN Circ. 10159) has been observed by Swift on 2009 11 12 with a 5 ks ToO started at 19:00 UT (trigger 020120). We have analysed 5.4 ks of XRT data in PC mode, from 100361 s to 115.3 ks after the INTEGRAL trigger. An X-ray source is detected at RA, Dec 137.82427, -45.92541 which is equivalent to: RA(J2000) = 09h 11m 17.82s Dec(J2000) = -45d 55' 31.5" with an uncertainty of 5.1 arcseconds (radius, 90% containment). The light curve is probably decaying but more data are needed to estimate the decay slope. A spectrum formed from the PC mode data (30 counts within a circular region of 15 pixel radius) can be fitted with an absorbed power-law with a photon spectral index of 2.5 (+5, -3.4) The best-fitting absorption column is < 5 x 10^22 cm-2, consistent with the Galactic value of 6.2 x 10^21 cm-2 (Kalberla et al. 2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 7.0 x 10^-11 (2.7 x 10^-10) erg cm^-2 count^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00020120. At the time of GRB 091111, the Swift/BAT was active, sensitive and pointing such that the burst was in the BAT field of view with 25% mask coding. There is no count rate increase detected in any of the four BAT energy bands This circular is an official product of the Swift-XRT team. [GCN OPS NOTE(30dec12): In response to S.Mereghetti's communication, this Subject-line was changed from "09111" to "091111".]