{
  "bibcode": "2007GCN..6186....1C",
  "body": "S. B. Cenko, A. M. Soderberg (Caltech), D. A. Frail (NRAO), and D. B. Fox\n(Penn State) report on behalf of a larger collaboration:\n\nThe Chandra X-ray Observatory + ACIS observed the field of GRB070125\n(Hurley et al, GCN 6024) beginning 5 March 2007 21:28 UT for a 30 ks\nexposure (mean epoch ~ 39.76 days after the burst).  No source is detected\nat the location of the optical afterglow (Cenko & Fox, GCN 6028).\nFormally, using a circular aperture with 1\" diameter, we detect 0.9 +/-\n5.0 photons from 0.3-10 keV.  Using spectral properties derived from early\nXRT observations (Gamma=2.0, nH=8e20; Racusin and Vetere, GCN 6030),\nwe estimate an upper limit on the afterglow flux of < 2e-15 erg cm^-2\ns^-1.\n\nHad the X-ray flux seen by the Swift XRT (Burrows & Racusin, GCN 6181)\ncontinued to decay as a single power-law with index ~ -1.5, we would\nexpect a flux ~ 5e-15 erg cm^-2 s^-1 at the Chandra epoch (~ 20 Chandra\nACIS-S photons), more than a factor of 2 above this upper limit.  We\ntherefore conclude the X-ray decay has steepened since the last XRT\ndetection, confirming the jet break seen in the optical light curve\n(Mirabal, Halpern, & Thorstensen, GCN 6096; Garnavich et al., GCN 6165).\n\nA plot of the X-ray light curve can be found at:\n\n   http://www.srl.caltech.edu/~cenko/public/grb070125_xray.jpg\n\nWe would like to thank the entire Chandra X-ray Center staff for their\nexecution of this observation and the rapid processing of the data.",
  "circularId": 6186,
  "createdOn": 1173475121000,
  "email": "cenko@srl.caltech.edu",
  "subject": "GRB 070125: Chandra X-ray Confirmation of Jet Break",
  "submitter": "S. Bradley Cenko at Caltech  <cenko@srl.caltech.edu>",
  "eventId": "GRB 070125"
}