{
  "bibcode": "1999GCN...208....1B",
  "body": "GRB 990123: Optical Decay Slope\n\nJ. S. Bloom, S. R. Kulkarni, S. G. Djorgovski, S. C. Odewahn, R. R. Gal,\nL. M. Lubin (CIT), and D. A. Frail (NRAO) note on behalf of the\nCaltech-CARA-NRAO GRB collaboration:\n\n\"After an initial rise to about 1 Jy, the early-time optical light-curve\nof the transient afterglow of GRB 990123 (as reported by the ROTSE Team;\nGCN #205) displayed a power-law decay.  We note here that the decay\nappears to be well-continued by the later time (~3 hours) optical fluxes\nof the transient discovered at Palomar (GCN #201; GCN #206; GCN #207).  \nThe decay constant is approximately alpha = -1.5 (defined as F_nu (t) =\nconst * t^alpha). This is consistent with the decay constants measured at\nlate-times in other GRB afterglows.\n\nThis suggests a strong phenomenological connection between the emission \nmechanism(s) at very early times (from tens of seconds to few minutes after \nthe burst) and at later times (>~ few hours).  The continuity of the power-law\nlight curve represents a strong constraint for theoretical models of optical \nemission from GRBs and their afterglows.\n\nA lightcurve, which will be actively updated, may be obtained at\nhttp://astro.caltech.edu/~jsb/GRB/grb990123.html\n\nThis message may be cited.\"",
  "circularId": 208,
  "createdOn": 917169130000,
  "email": "jsb@astro.caltech.edu",
  "subject": "GRB 990123: Optical Decay Slope",
  "submitter": "Josh Bloom at CIT  <jsb@astro.caltech.edu>",
  "eventId": "GRB 990123"
}