GCN Circular 428
Subject
GRB 991014, Optical Observations
Event
Date
1999-10-23T02:11:34Z (26 years ago)
From
Jules Halpern at Columbia U. <jules@astro.columbia.edu>
R. Uglesich, J. Halpern (Columbia U.), & J. Thorstensen (Dartmouth)
report:
"In addition to the MDM observations reported in GCN #423, we
reobserved the entire 6' radius error circle of the BeppoSAX WFC
(Gandolfi, GCN #417) with the 1.3m because it is not known if either
of the reported NFI X-ray sources (in 't Zand et al. GCN #427) is
associated with the GRB. The 1.3m observations were centered on
Oct. 15.45 UT and Oct. 16.48 UT, and reach a 5-sigma limiting
magnitude of R = 22.6 on the first night, and R = 22.8 on the second
night. We used a non-standard, broad R filter which nevertheless
calibrates very well with Landolt (1992) standards that we obtained.
We find R = 17.64 for the star mentioned in GCN #423, which is consistent
with the USNO calibration (R = 17.61 +/- 0.02). Although we have not yet
carried out a detailed photometric analysis of the entire WFC circle,
careful visual inspection reveals no variable object to a limit of
approximately R > 22.6 at 13 hours after the burst. The images from
the MDM 2.4 reported in GCN #423 cover the error circles of both of
the NFI sources, and our previously reported limit of R > 23.1 at
11.2 hours still applies.
We also note that Galactic extinction in this direction is estimated
to be E(B-V) = 0.202 from IRAS dust maps (Schlegel et al. 1998),
so A_R is a modest 0.54 magnitudes.
A CCD image of the field of the NFI sources is posted at
http://www.astro.bio2.edu/grb/
This message may be cited."