{
"subject": "GRB 120711A: Swift-XRT observations",
"bibcode": "2012GCN.13442....1B",
"createdOn": 1342011600000,
"circularId": 13442,
"submitter": "Andy Beardmore at U Leicester ",
"email": "ab271@leicester.ac.uk",
"body": "A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the\nSwift-XRT team:\n\nWe have analysed 657 s of XRT data for the INTEGRAL-detected burst: GRB\n120711A (Gotz et al. GCN Circ. 13434), from 8.3 ks to 20.0 ks after the\n INTEGRAL trigger. The data comprise 269 s in Windowed Timing (WT) mode\nwith the remainder in Photon Counting (PC) mode. An X-ray source is\ndetected within the INTEGRAL error circle. Using 336 s of PC mode data\nand 1 UVOT images, we find an enhanced XRT position (using the XRT-UVOT\nalignment and matching UVOT field sources to the USNO-B1 catalogue):\nRA, Dec = 94.67830, -70.99905 which is equivalent to:\n\nRA (J2000): 06h 18m 42.79s\nDec(J2000): -70d 59' 56.6\"\n\nwith an uncertainty of 1.7 arcsec (radius, 90% confidence). This\nposition is 29 arcsec from the INTEGRAL position and 0.3 arcsec from\nthe Skynet/PROMPT position (LaCluyze et al. GCN Circ. 13430). \n\nThe light curve can be modelled with a power-law decay with a decay\nindex of alpha=1.59 (+0.16, -0.15).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 2.15 (+/-0.11). The\nbest-fitting absorption column is 3.6 (+/-0.4) x 10^21 cm^-2, in\nexcess of the Galactic value of 7.9 x 10^20 cm^-2 (Kalberla et al.\n2005). The PC mode spectrum has a photon index of 1.80 (+0.25, -0.23)\nand a best-fitting absorption column of 2.4 (+0.9, -0.8) x 10^21 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum is 4.5 x 10^-11 (6.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t 2.4 (+0.9, -0.8) x 10^21 cm^-2\nGalactic foreground: 7.9 x 10^20 cm^-2\nExcess significance: 3.2 sigma\nPhoton index:\t 1.80 (+0.25, -0.23)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00020223.\n\nThis circular is an official product of the Swift-XRT team."
}