{
  "bibcode": "2010GCN.10316....1K",
  "body": "H. A. Krimm (CRESST/GSFC/USRA), P. Romano, S. Vercellone (INAF-IASF Palermo),\nS. D. Barthelmy (GSFC), W. Baumgartner (CRESST/GSFC/UMBC),\nJ. Cummings (CRESST/GSFC/UMBC), E. Fenimore (LANL), N. Gehrels (GSFC),\nC. B. Markwardt (CRESST/GSFC/UMD), D. Palmer (LANL),\nT. Sakamoto (CRESTT/GSFC/UMBC), G. Skinner (CRESST/GSFC/UMD),\nM. Stamatikos (OSU/GSFC), J. Tueller (GSFC), T. Ukwatta (GSFC/GWU)\n\nAt 00:58:50.58 UT on 2010-Jan-08 (MJD 55204), Swift/BAT triggered on a\nrapid outburst from XTE J1901+014.  The trigger was a 128-second image\ntrigger and detectable emission lasted from T-150 sec to at least T+250\nsec, when the spacecraft moved away from the field due to a pre-planned\nslew.  The time-averaged spectrum from T-137.5 to T+263.9 sec is best fit\nby a simple power-law model.  The photon power law index of the time-averaged\nspectrum is 5.22 +- 0.51.  The fluence in the 15-150 keV band is 1.5 +-\n0.2 x 10-6 erg/cm2.  This corresponds to 0.056 � 0.010 ct/s/cm2 or 250\nmCrab in the 15-50 keV band. Due to an observing constraint (proximity\nto the sun), no Swift XRT or UVOT observations will be possible until 2010-Feb-16.\n\nThis is the second time Swift/BAT has triggered on XTE J1901+014.  The\nfirst was on  2006-June-06 at 10:17:18.76 for a weaker flare.  The time-averaged\nspectrum of the 2006 flare from T+0.0 to T+33.1 sec was best fit by a simple\npower-law model.  The photon power law index of the time-averaged spectrum\nwas 4.32 +- 1.94 and the fluence in the 15-150 keV band was 1.1 +- 0.7\nx 10-7 erg/cm2.  The flux in a 1984-second observation beginning at 10:17:18\naveraged 0.068 � 0.048 ct/s/cm2 (31 mCrab, 15-50 keV).\n\nXTE J1901+014 is normally barely detectable in the BAT hard X-ray transient\nmonitor at ~2.5 mCrab.  It has shown signs of increased, but variable,\nactivity since about 2009-Dec-03.\n\nThis source was discovered in 2002 (Remillard and Smith, ATel #88) and\nis known for having rapid, intense variations in its X-ray flux (e.g. Smith\net al, ATel #1268). The true nature of the source is still in question.\nOptical photometry of the field suggests a low mass companion and the\nsource may be the first low-mass fast X-ray transient (Karasev, Lutovinov\n& Burenin, 2008, Astron. Lett., 34, 753).  This recent trigger tells us\nthat XTE J1901+014 has again become active, so further observations are\nencouraged.\n\nNote that the trigger number in the recent GCN Circular (Palmer, Cummings and \nSakamoto, GCN Circular #10315) is incorrect.  The subject line should have \nreferred to Swift/BAT trigger #382159.  Trigger #382180 was correctly identified \nonboard as XTE J1901+014.",
  "circularId": 10316,
  "createdOn": 1262963980000,
  "email": "hans.krimm@nasa.gov",
  "subject": "Swift/BAT Detects an Outburst from XTE J1901+014",
  "submitter": "Hans Krimm at NASA-GSFC  <hans.krimm@nasa.gov>"
}