{
  "bibcode": "2007GCN..6096....1M",
  "body": "N. Mirabal, J. Halpern (Columbia U.), & J. R. Thorstensen (Dartmouth)\nreport on behalf of the MDM Observatory GRB follow-up team:\n\n\"We obtained several observations of the afterglow of GRB 070125\n(Cenko & Fox, GCN 6028) between 2 and 12 days after the burst using the\nMDM 2.4m and 1.3m telescopes.  Results in the R-band are summarized as\nfollows:\n\n             ---------------------------------------\n               Date(UT)   t-t0(days)  R(mag)   +/-\n             ---------------------------------------\n              Jan 27.270     1.964     19.71   0.02\n              Jan 28.299     2.993     20.44   0.03\n              Jan 29.346     4.040     21.07   0.07\n              Feb  6.307    12.001    >23.8\n             ---------------------------------------\n\nCalibration was performed with Landolt standard stars.  In addition, we\ncompiled\ndata from the GCN circulars, and placed them on a common scale using their\nstated\ncalibrators.  MDM images and the compiled R-band light curve are shown at:\n\nhttp://www.astro.columbia.edu/~jules/grb/070125/\n\nThe light curve shows an apparent plateau or rise at about 1 day.  Between 1\nand 4 days, it is well described by a power law of slope -1.6.  Our upper\nlimit\nat 12 days implies that a break occurred after 4 days, and that the slope\nbecame steeper than -2.2.   At redshift z=1.55 (Fox et al., GCN 6071) and\nfluence 1.5x10^-4 erg cm^-2 (Bellm et al., GCN 6025), the assumed isotropic\nenergy is 9x10^53 erg.  If we treat 4 days as a lower limit on the time\nof any \"jet break\", then the jet opening angle is of order 6 degrees or\ngreater, and the beamed energy is 6x10^51 erg or greater.\n\nThis message may be cited.\"",
  "circularId": 6096,
  "createdOn": 1171152441000,
  "email": "jules@astro.columbia.edu",
  "subject": "GRB 070125: Break in Optical Decay",
  "submitter": "Jules Halpern at Columbia U.  <jules@astro.columbia.edu>",
  "eventId": "GRB 070125"
}