{
  "bibcode": "2015GCN.17469....1O",
  "body": "J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Maselli \n(INAF-IASFPA), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB), D.N.\nBurrows (PSU), J.A. Kennea (PSU), B. Sbarufatti (INAF-OAB/PSU) and C.\nPagani report on behalf of the Swift-XRT team:\n\nWe have analysed 8.5 ks of XRT data for GRB 150213B (Pagani et al. GCN\nCirc. 17464), from 133 s to 23.5 ks after the  BAT trigger. The data\ncomprise 414 s in Windowed Timing (WT) mode (the first 9 s were taken\nwhile Swift was slewing) with the remainder in Photon Counting (PC)\nmode. The refined XRT position is RA, Dec = 253.4520, +34.1884 which is\nequivalent to:\n\nRA (J2000): 16 53 48.49\nDec(J2000): +34 11 18.4\n\nwith an uncertainty of 3.6 arcsec (radius, 90% confidence).\n\nThe light curve can be modelled with a series of power-law decays. The\ninitial decay index is alpha=1.18 (+0.09, -0.10). At T+310 s  the decay\nsteepens to an alpha of 2.46 (+0.26, -0.23) before breaking again at\nT+2218 s to a final decay with index alpha=1.33 (+0.24, -0.21).\n\nA spectrum formed from the WT mode data can be fitted with an absorbed\npower-law with a photon spectral index\tof 1.86 (+0.05, -0.04). The\nbest-fitting absorption column is  5.1 (+/-1.0) x 10^20 cm^-2, in\nexcess of the Galactic value of 1.9 x 10^20 cm^-2 (Willingale et al.\n2013). The PC mode spectrum has a photon index of 1.74 (+0.29, -0.26)\nand a best-fitting absorption column of 6.7 (+7.9, -4.8) x 10^20 cm^-2.\nThe counts to observed (unabsorbed) 0.3-10 keV flux conversion factor\ndeduced from this spectrum  is 3.7 x 10^-11 (4.2 x 10^-11) erg cm^-2\ncount^-1. \n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     6.7 (+7.9, -4.8) x 10^20 cm^-2\nGalactic foreground: 1.9 x 10^20 cm^-2\nExcess significance: <1.6 sigma\nPhoton index:\t     1.74 (+0.29, -0.26)\n\nIf the light curve continues to decay with a power-law decay index of\n1.33, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.9 x\n10^-14 (6.6 x 10^-14) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00631051.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 17469,
  "createdOn": 1423910826000,
  "email": "pae9@leicester.ac.uk",
  "subject": "GRB 150213B: Swift-XRT refined Analysis",
  "submitter": "Phil Evans at U of Leicester  <pae9@leicester.ac.uk>",
  "eventId": "GRB 150213B"
}