{
  "bibcode": "2014GCN.16428....1D",
  "body": "M. De Pasquale (IASF-Palermo) reports on behalf of the Swift-XRT team:\n\nWe have analysed 3.0 ks of XRT data for the Fermi/GBM-detected\nburst GRB 140620A (Fitzpatrick et al., GCN circ 16426), from 37.6\nks to 43.9 ks after the Fermi/GBM trigger. The data are entirely\nin Photon Counting (PC) mode.\nAn X-ray source is detected within the Fermi/GBM error circle\nat the position of the iPTF transient (Kasliwal et al., GCN circ.\n16425). Using 2966 s of PC mode data and 2 UVOT images, we find an\nenhanced XRT position (using the XRT-UVOT alignment and matching\nUVOT field sources to the USNO-B1 catalogue): RA, Dec = 281.87089,\n+49.73093 which is equivalent to:\n\nRA (J2000): 18h 47m 29.01s\nDec(J2000): +49d 43' 51.4\"\n\nwith an uncertainty of 2.2 arcsec (radius, 90% confidence). This\nis 0.4 arcsec from the iPTF position.\n\nThe late-time light curve (from T0+37.6 ks) is consistent with a\nconstant source of mean count rate 1.2e-01 ct/sec. A power-law fit\nformally gives an index of -0.1 (+2.4, -1.3). Further observations\nmight be needed to confirm that this source is the X-ray afterglow\nof 140620A.\n\nA spectrum formed from the PC mode data can be fitted with an\nabsorbed power-law with a photon spectral index of 2.04 (+0.26,\n-0.24). The best-fitting absorption column is 1.4 (+0.7, -0.6) x\n10^21 cm^-2, in excess of the Galactic value of 5.2 x 10^20 cm^-2\n(Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10\nkeV flux conversion factor deduced from this spectrum is 3.3 x 10^-11\n(4.3 x 10^-11) erg cm^-2 count^-1.\n\nA summary of the PC-mode spectrum is thus:\n\nTotal column:         1.4 (+0.7, -0.6) x 10^21 cm^-2\nGalactic foreground: 5.2 x 10^20 cm^-2\nExcess significance: 2.3 sigma\nPhoton index:         2.04 (+0.26, -0.24)\n\nIf the light curve continues to evolve with a power-law index\nof -0.1, the count rate at T+24 hours will be 0.13 count s^-1,\ncorresponding to an observed (unabsorbed) 0.3-10 keV flux of 4.3 x\n10^-12 (5.6 x 10^-12) erg cm^-2 s^-1.\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00020387.\n\nThis circular is an official product of the Swift-XRT team.",
  "circularId": 16428,
  "createdOn": 1403360064000,
  "email": "maselli@ifc.inaf.it",
  "subject": "GRB 140620A: Swift-XRT observations",
  "submitter": "Alessandro Maselli at INAF/IASF Palermo  <maselli@ifc.inaf.it>",
  "eventId": "GRB 140620A"
}