{
  "bibcode": "1998GCN....92....1G",
  "body": "GRB 980519 Optical Observations\n\nR. R. Gal, J. S. Bloom, S. G. Djorgovski, and S. R. Kulkarni on behalf\nof the Caltech GRB Collaboration, report:\n\n\"In addition to the I and R photometry reported by Bloom et al. (GCN\n#87), we have photometered the B and V Palomar 200inch images of the\nfield of GRB 980519.  Derived magnitudes of the following 7 secondary\nstars are in the Landolt BV system (see GCN #87 for details):\n\nStar      B    err(B)    V    err(V)\nA       19.51  0.13    18.31  0.12\nB       21.74  0.34    20.05  0.09\nC       19.27  0.11    18.35  0.08\nE       22.88  0.11    21.07  0.24\nF       22.61  0.17    20.83  0.13\nG       21.51  0.19    19.74  0.10\nH       21.94  0.29    20.26  0.13\n\n\nThe derived magnitudes of the OT are:\n\n         May 20.4485 UT, B = 22.53 +/- .14\n         May 20.466  UT, V = 21.74 +/- .16\n             \n         May 21.448 UT, B > 22.9 (3-sigma upper limit)\n         May 21.476 UT, V > 22.0 (3-sigma upper limit) \n\nThe non-detection on May 21 is consistent with the power-law decline\nslope of beta = -1.98 reported in Djorgovski et al. (GCN #79).\nMoreover, broadband colors circa May 20.4 (BV reported herein; RI\nreported in Bloom #87) suggest a spectral index of alpha = -1.26 +/-\n0.3. This is also consistent with the simple blastwave model\n(eg. Wijers, Rees and Meszaros MNRAS 288, L51.) prediction that alpha\n= (2/3) beta.  The V-band point is somewhat higher (~3 sigma) than the\nextrapolated spectrum, suggesting the spectrum of the transient may\nnot have been a pure power-law.  Lastly, given the general consistency\nof spectral slope with flux time decay, we note the absence of strong\nextinction in the OT (in contrast to GRB 980329).\n\nThis report may be cited.\"",
  "circularId": 92,
  "createdOn": 896140693000,
  "email": "rrg@astro.caltech.edu",
  "eventId": "GRB 980519",
  "subject": "GRB 980519 Optical Observations",
  "submitter": "Roy Gal at CalTech  <rrg@astro.caltech.edu>"
}