{
  "bibcode": "2013GCN.14973....1D",
  "body": "P. D'Avanzo (INAF-OAB), B. Porterfield, D. N. Burrows, M. Siegel  \n(PSU), A. Melandri (INAF-OAB), P. A. Evans (Univ. Leicester) report on  \nbehalf of the Swift team:\n\nThe Fermi GBM and LAT instruments detected GRB 130702A at 00:05:23 UT  \non July 2, 2013 (Fermi trigger 394416326; Cheung et al. 2013, GCN Circ  \n14971). Followup by the Palomar Transient Factory (PTF) located a  \npossible optical counterpart, iPTF13bxl (Singer et al. 2013, GCN Circ.  \n14967).  A subsequent TOO observation by Swift located a coincident X- \nray counterpart, making this a likely counterpart of GRB 130702A  \n(Singer et al. 2013, GCN Circ 14971). Here we report the results of  \nthe analysis of Swift XRT and UVOT data for this object.\n\nWe have analysed 3.4 ks of XRT data for this object,  from 89.1 ks to  \n95.7 ks after the Fermi/GBM trigger.  The data are entirely in Photon  \nCounting (PC) mode.  Using 3411 s of PC mode data and 5 UVOT images,  \nwe find an enhanced XRT position (using the XRT-UVOT alignment and  \nmatching UVOT field sources to the USNO-B1 catalogue): RA, Dec =  \n217.31166, +15.77388 which is equivalent to:\n\nRA (J2000): 14h 29m 14.80s\nDec(J2000): +15d 46' 26.0\"\n\nwith an uncertainty of 1.5 arcsec (radius, 90% confidence). This  \nposition is consistent with the optical counterpart reported by Singer  \net al. 2013 (GCN Circ. 14967; see also Guidorzi et al. 2013, GCN Circ.  \n14968).\n\nThe light curve displays variability consistent with a fading  \nbehaviour. More observations are scheduled to confirm whether the  \nsource is fading.\n\nA spectrum formed from the PC mode data can be fitted with an absorbed  \npower-law with a photon spectral index of 1.99 (+/-0.16). The best- \nfitting absorption column is  6.3 (+3.4, -3.1) x 10^20 cm^-2, in  \nexcess of the Galactic value of 1.7 x 10^20 cm^-2 (Kalberla et al.  \n2005). The counts to observed (unabsorbed) 0.3-10 keV flux conversion  \nfactor deduced from this spectrum  is 3.6 x 10^-11 (4.2 x 10^-11) erg  \ncm^-2 count^-1.\n\nA summary of the PC-mode spectrum is thus:\nTotal column:\t     6.3 (+3.4, -3.1) x 10^20 cm^-2\nGalactic foreground: 1.7 x 10^20 cm^-2\nExcess significance: 2.4 sigma\nPhoton index:\t     1.99 (+/-0.16)\n\nThe results of the XRT-team automatic analysis are available at\nhttp://www.swift.ac.uk/xrt_products/00032876.\n\n\nThe Swift/UVOT began settled observations of the field of GRB 130702A  \n89111 s after the GBM detection.  A source consistent with the P48  \nposition (Singer et al. 2013, GCN Circ. 14967) is detected in the  \ninitial UVOT exposures.\n\nThe preliminary UVOT position is:\n    RA  (J2000) =  14:29:14.77 = 217.31155 (deg.)\n    Dec (J2000) = +15:46:26.5  =  15.77403 (deg.)\nwith an estimated uncertainty of 0.50 arc sec. (radius, 90% confidence).\n\nPreliminary detections using the UVOT photometric system (Breeveld et  \nal. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:\n\nFilter         T_start(s)   T_stop(s)      Exp(s)           Mag\n\nwhite            89232        95967          3414         18.26 +/- 0.04\n\nThe magnitudes in the table are not corrected for the Galactic  \nextinction due to the reddening of E(B V) = 0.04 in the direction of  \nthe burst (Schlegel et al. 1998).\n\n\nThis circular is an official product of the Swift team.",
  "circularId": 14973,
  "createdOn": 1372878100000,
  "email": "andrea.melandri@brera.inaf.it",
  "subject": "Fermi GRB 130702A: Swift XRT and UVOT observations",
  "submitter": "Andrea Melandri at INAF-OAB  <andrea.melandri@brera.inaf.it>",
  "eventId": "GRB 130702A"
}