{
  "bibcode": "1998GCN...136....1B",
  "body": "GRB 980703 Transient Optical Follow-Up\n\nJ. S. Bloom, S. J. Djorgovski, S. R. Kulkarni (CIT) and D. A. Frail (NRAO)\nreport on behalf of the Caltech-NRAO GRB collaboration: \"In the GRB 980703\nfield (IAUC #6966; GCN #126; GCN #127) of the radio/optical transient\ndiscovered by Frail et al. (GCN #128), R-band images (10 min) were\nobtained at the Palomar 60 inch on July 4,5 by R. O. Marzke (Carnegie) and\nD. R. Patton (U. Victoria) and at the Keck-II 10-m on LRIS by J. B. Oke\n(DAO), K. D.  Horne (U. St Andrews), and R. Gomer.  Photometry, based on\nan approximate LRIS zero-point (which is uncertain to ~0.2 mag), results\nin the following derived magnitudes for the transient:\n \nDate (UT)    Intr     Mag OT Rc\n-----------------------------------\nJul 4.477    P60    21.3 +/- 0.2\nJul 5.482    P60    21.8 +/- 0.3   \nJul 6.607    LRIS   22.03 +/- 0.02  (+ zero point uncertainty 0.2mag\n                                       for all three points)  \n\nThe zero-point may change with expected calibrations but the slope will\nnot. The fading a power-law decline of -0.74, consistent with the I-band\nfading (-0.84) found from data in Vreeswijk et al. (GCN 132), would make\nthis OT the slowest fading counterpart to a GRB yet.  However, since the\ndecay appears somewhat stronger at earlier epochs, we believe that the\nlight may be contaminated by an underlying host.  If true, the light curve\nshould show even more flattening.  This hypothesis appears corroborated by\nthe fact that the spectral indices derived from the I/R/H-band data are\nnot consistent with a simple fireball model prediction from the decay\nconstant. A summary light curve with all reported I/R-band data may be\nfound at http://astro.caltech.edu/~jsb/grb980703_ltcurve.ps\"\n\nThis message is citeable.",
  "circularId": 136,
  "createdOn": 899860163000,
  "email": "jsb@astro.caltech.edu",
  "subject": "GRB980703 Transient Optical Follow-Up",
  "submitter": "Josh Bloom at CIT  <jsb@astro.caltech.edu>",
  "eventId": "GRB 980703"
}