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GCN Circular 428

GRB 991014, Optical Observations
1999-10-23T02:11:34Z (25 years ago)
Jules Halpern at Columbia U. <>
R. Uglesich, J. Halpern (Columbia U.), & J. Thorstensen (Dartmouth)

"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

This message may be cited."
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