{
  "bibcode": "2015GCN.17544....1M",
  "body": "Alessandro Maselli (INAF-IASFPA), Phil Evans (U. Leicester),\nDavid Burrows (PSU), Sergio Campana (INAF-OAB),\nNeil Gehrels (GSFC), Jamie Kennea (PSU), Amy Lien (GSFC/UMBC),\nDaniele Malesani (DARK/NBI), Craig. B. Markwardt (GSFC),\nFrank Marshall (GSFC), Julian Osborne (U. Leicester),\nDavid. M. Palmer (LANL), Kim L. Page (U Leicester),\nRhaana L. C. Starling (U Leicester)\nreport on behalf of the Swift team:\n\nSwift continues to observe the field of BAT trigger 633105\n(aka GRB 150301C) with sky location in M31. To avoid further\nnaming confusion, this object will be referred as Swift J0045.2+4151\nhereafter. The XRT continues to detect only a single source within\nthe BAT error circle at a position coincident with the previously\nknown XMM-Newton source, [PFH2005] 622 (Pietsch et al. 2005).\nFor the rest of this circular we assume that the X-rays detected by\nXRT are from [PFH2005] 622.\n\nThe XRT has acquired four observations so far. The source\n(which we presume is [PFH2005] 622) was detected in the first snapshot,\n(T0+107s to T0+720s), in which we detect 8 events in 614 seconds,\nwith a mean background expectation of 0.34 counts.  This results in a rate\nof 1.48 (+0.6, -0.5) e-2 counts/s (1 sigma errors).\n\nIn the 2nd epoch (T0+4 ks to T0+80 ks), we detect 3 events in 7.2 ks, with\nan expected background of 1.25 events, giving a 3 sigma upper limit of\n< 0.002 counts/s.\n\nIn the 3rd epoch (T0+171 ks to T0+206 ks), we find 5 events in 4.8 ks with a\nmean background expectation of 0.64 events, giving a 3 sigma detection\nof 1.2 (+0.8, -0.6) e-3 counts/s (1 sigma errors).\n\nAll measurements use a source radius of 9 pixels (21 arcseconds),\na background measurement from an annulus around the source region, and\nthe Bayesian method of Kraft, Burrows, and Nousek (1991, ApJ, 374, 344) to obtain\nthe 1-sigma confidence intervals (for detections) or 3-sigma upper limits (for non-detections).\n\nTherefore, after a detection in the initial XRT observation, the source\nfaded below the XRT detection limit and may have brightened again\nin the 3rd epoch.\n\nWe cannot conclude firmly at this point whether the source\n[PFH2005] 622 is associated with the BAT trigger or not.\nMore observations at all wavelengths are encouraged.\n\nA table and a light curve that summarize current XRT observations\nof [PFH2005] 622 are available at:\nhttp://swift.gsfc.nasa.gov/results/BATbursts/633105/xrt/atel_20150304.html\n\n[GCN OPS NOTE(05mar15), Per author's request, the last line in the 5th paragraph\nwas changed from \"the 3 sigma confidence regions and upper limits.\"\nto \"the 1-sigma confidence intervals (for detections) or 3-sigma upper limits (for non-detections).\".\nAnd the places in the 2nd & 4th paragraphs that said \"(1 sigma errors)\"\nwere changed to \"(1 sigma errors)\".]",
  "circularId": 17544,
  "createdOn": 1425510463000,
  "email": "amy.y.lien@nasa.gov",
  "subject": "Further X-ray observations of  Swift J0045.2+4151 (aka Sw J0045 aka GRB 150301C aka [PFH2005] 622)",
  "submitter": "Amy Lien at GSFC  <amy.y.lien@nasa.gov>",
  "eventId": "GRB 150301C"
}