{
  "bibcode": "2005GCN..4274....1D",
  "body": "A.De Luca, P.Caraveo, P.Esposito, S.Mereghetti, A.Tiengo (INAF/IASF Mi),\nreport:\n\nwe have analyzed the data from the XMM-Newton observation of\nthe soft short burst GRB050925, observed by Swift to have\ncharacteristics similar to that of Soft Gamma Repeaters (SGRs)\n(Holland et al., GCN4034). An independent analysis of the XMM\ndata was reported by Rea et al.(GCN4264).\n\nWe give here the detailed results of a source detection on the\nEPIC dataset. Such results will become an important reference\nin case the putative SGR will enter a phase of enhanced activity.\n\nWe used independently the pn camera data and the combined\nMOS1+MOS2 data. We selected the energy ranges 0.3-2 keV,\n2-8 keV and 0.3-8 keV. The MOS and pn positions are found to\nbe consistent within ~1.5 arcsec, in agreement with the known\nastrometric accuracy of the EPIC cameras. Thus, we assume 1.5\narcsec as the 1sigma uncertainty on the X-ray sources' positions.\nIn the source list below we quote the J2000 coordinates\nas derived from the pn camera (unless otherwise specified).\n\nSince the field of GRB050925 is very crowded we focus on the\nregion closer to the 1.5 arcmin BAT error circle (Markwardt\net al., GCN4037). 6 X-ray sources (named XMM1...XMM6) are\ndetected within 2 arcmin of the BAT coordinates.\n\nFinding charts from pn and MOS data may be found at\nhttp://www.iasf-milano.inaf.it/~deluca/grb050925\nPlease note that the circles around XMM sources are meant\nto help locate them. In the scale used for the figures the\nXMM error boxes are smaller than 1 pixel.\n\nSources inside the BAT circle:\n\nXMM1 - RA 20:13:47.81, Dec +34:19:51.9 - it is the brightest\n       source located within the BAT error circle. It is the\n       steady source discovered in Swift/XRT data by Beardmore\n       et al. (GCN4043) and interpreted as a field star.\n       Its coordinates, within errors, are consistent with a bright\n       optical source (B~12.4, R~11.9, source id.1243-0400741 in\n       USNO-B1). Its spectrum is well described by a mekal plasma\n       model with NH<5x10^20 cm^-2, kT~0.6 keV, abundance ~0.3 solar\n       values and observed flux of 2.7x10^-14 erg cm^-2 s^-1\n       in 0.3-8 keV. The resulting Fx/Fopt is of ~3x10^-4.\n       Thus, in agreement with Beardmore et al.(GCN4043), we\n       conclude that source XMM1 is most likely a nearby star.\n       Rea et al.(GCN4264), assuming a smaller X-ray error circle,\n       questioned the association with the bright optical source\n\nXMM2 - RA 20:13:57.85, Dec +34:19:56.5 - detected with S/N~3,\n       in the 0.3-2 keV range only.\n       Assuming a Crab spectrum with Galactic absorption\n       (1.1x10^22 cm^-2 according to Dickey & Lockman, 1990), its\n       observed flux is (2-3)x10^-15 erg cm^-2 s^-1 (0.3-2 keV).\n       No obvious optical counterparts are found in the DSS plates.\n\nSources outside the BAT circle:\n\nXMM3 - RA 20:13:54.97, Dec +34:18:22.4 - located at 1.55 arcmin\n       from the BAT position, it is detected with S/N~3\n       in MOS data only (in the pn detector it lies on a bad column),\n       with a flux  similar to source XMM2.\n       An optical source with R~17 is found within 3 arcsec.\n\nXMM4 - RA 20:13:56.06, Dec +34:21:28.9 - located at 1.61 arcmin\n       from the BAT position, it is detected with S/N~3\n       in MOS data only (in the pn detector  it lies on a bad column),\n       with a flux similar to source XMM2.\n       An optical source with R~16.5 is found within 2.2 arcsec.\n\nXMM5 - RA 20:14:01.59, Dec +34:21:03.1 - located at 1.89 arcmin\n       from the BAT position, it lies within 1.5 arcsec of a\n       bright optical source (B~13.1, R~11.4, source id.1243-0401091\n       in USNO-B1 catalog), its spectrum is consistent with a mekal\n       plasma model with absorption smaller than the Galactic value,\n       kT~0.67 keV and abundance ~0.4 solar values; the observed flux\n       is ~1x10^-14 erg cm^-2 s^-1 (0.2-5 keV). Fx/Fopt is ~10^-4.\n       It is most likely  a star.\n\nXMM6 - RA 20:13:45.17, Dec +34:20:23.8 - located at 1.93 arcmin\n       from the BAT position, its spectrum is consistent\n       with a power law (photon index ~1.8) absorbed by the Galactic\n       column. Its observed flux is ~2x10^-14 erg cm^-2 s^-1\n       (0.2-8 keV). No obvious optical counterparts.\n\nNo other sources within 2 arcmin of the BAT position are seen.\nUsing the present XMM observation we can estimate the upper limit\nflux as follows: assuming a Crab-like spectrum with Galactic\nabsorption, a S/N=3 detection corresponds to a flux of ~3x10^-15 erg\ncm^-2 s^-1 in the 0.3-2 keV band and ~8x10^-15 erg cm^-2 s^-1 in\nthe 0.3-8 keV band.\n\nWe thank the XMM Project Scientist, N.Schartel, for approval of\nthis TOO, and the XMM people at Vilspa for performing it.",
  "circularId": 4274,
  "createdOn": 1132080285000,
  "email": "deluca@iasf-milano.inaf.it",
  "subject": "GRB050925: analysis of the XMM-Newton observation",
  "submitter": "Andrea De Luca at IASF-CNR,Milano  <deluca@iasf-milano.inaf.it>",
  "eventId": "GRB 050925"
}