GCN Circular 495
Subject
GRB991216 Optical and IR observations
Event
Date
1999-12-19T00:15:32Z (26 years ago)
From
Peter Garnavich at Center for Astrophysics <peterg@mars.harvard.edu>
P. Garnavich, S. Jha, K. Stanek, M. Pahre, M. Garcia, A. Szentgyorgyi
(CfA) and J. Tonry (U. Hawaii) report:
The object reported by Uglesich et al. (GCN 472) as a possible
afterglow of GRB991216 is detected on 5 sets of 120 sec. exposures
taken with the FLWO 1.2m+IRCam on Dec. 17 (UT) and on two sets of 540
sec. images taken Dec 18. A preliminary calibration provides the
following brightness estimates:
UT Date J err
Dec. 17.35 16.99 0.05
Dec. 18.30 18.25 0.06
The power-law index derived from these data is -1.33. Our Dec. 18.
point is significantly fainter than the J-band observation reported by
Vreeswijk et al. (GCN 492) (UT 18.13).
The afterglow was again observed with the Hawaii 2.2-m in the R band
and calibrated using star "B" (Jha et al. GCN 476) with R=19.45 (Dolan
et al. GCN 486). These new brightness estimates are:
UT Date R err
Dec 18.32 20.32 0.05
Dec 18.56 20.57 0.05
and when combined with previous R-band observations reported by Dolan
et. al (GCN 486), Henden et al. (GCN 473) and Jha et al. (GCN 476),
give a power-law index of -1.23+/-0.05. The Dec. UT 18.191 R-band
magnitude of 21.1 reported by Mattox (GCN 487) is significantly fainter
than our measurements.
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