{
  "bibcode": "2002GCN..1392....1F",
  "body": "D. W. Fox (Caltech) reports on behalf of the Caltech-NRAO GRB\nCollaboration:\n\n\"We have observed the error region of the X-ray flash XRF020427 (GCN\n1383, 1384, 1386) with the Chandra X-ray Observatory for 12.5 ksec\nbeginning May 14.1939 UT.  Reduction of the data using standard Ciao\nprocedures, and comparison with the source catalog from our first\nobservation of May 6.2456 UT (GCN 1387), yields the following results\nfor the BeppoSAX NFI error circle (Amati et al., GCN 1386):\n\n    ID        IAU Name          CR_1    CR_2    Delta   \n   =======================================================\n     1  CXOU J220928.2-651932   4.2(6)  1.8(4)  -3.3 sigma\n     2  CXOU J220925.9-651855   1.2(3)  2.3(4)  +2.1\n     3  CXOU J220925.0-651919   1.1(3)  0.8(3)  -0.7\n   =======================================================\n\nwhere \"CR_1\" and \"CR_2\" are the source count rates per ksec in the 0.3\nto 7.0 keV band for the first and second Chandra observations,\nrespectively, and \"Delta\" is the signed significance of the change in\ncount rate from the first to the second observation, expressed in\nstandard deviations.  Uncertainties in the trailing digits are\nindicated in parentheses.  \n\nThe brightest source in the first epoch, CXOU J220928.2-651932 (ID 1),\nshows a pronounced fading between the two epochs, equivalent to a\npower-law decay with index 1.3 referenced to the epoch of the burst\n(Apr 27.1588).  We conclude that this source is the likely X-ray\nafterglow of XRF020427.  \n\nIn addition, identification of three USNO stars on the Chandra images\nhas allowed us to improve the aspect; the improved position of the\nlikely afterglow (ID 1) is\n\n    RA  22:09:28.265(46),  Dec -65:19:31.78(32)  (J2000)\n\nwhere the uncertainties are indicated in parentheses and correspond to\nan average radial uncertainty of 0.3 arcsec (one-sigma).\"",
  "circularId": 1392,
  "createdOn": 1021921971000,
  "email": "derekfox@astro.caltech.edu",
  "subject": "XRF020427: Chandra Identification of a Likely X-ray Counterpart",
  "submitter": "Derek Fox at CIT  <derekfox@astro.caltech.edu>"
}