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GCN Circular 381

GRB 990705, R-band observations
1999-07-08T18:08:40Z (25 years ago)
Jules Halpern at Columbia U. <>
J. Halpern (Columbia U.), G. Jacoby (NOAO), F. Frontera (ITESRE-CNR, Bologna),
M. Feroci, E. Costa (IAS-CNR, Rome), and L. Piro (ITESRE-CNR, Frascati)

"We (GJ) observed the BeppoSAX NFI error circle of GRB 990705
(Gandolfi GCN #373) in the R band using the CTIO 1.5m telescope.
A 10 minute exposure was obtained on July 7.44 UT in seeing
of 1.4 arcsec, and 20 minutes were obtained on July 8.42 UT
in seeing of 1.6 arcsec.  At precisely the position quoted for
the fading infrared transient (Palazzi et al. GCN #377),
we see nothing to a 3-sigma limiting magnitude of R < 22.0
on July 7, and R < 22.3 on July 8.  Photometric calibration
was performed using the Landolt standard field of PG 0231+051.
For reference we measure R = 16.45 for the neighboring USNO-A2.0
star at RA 05:09:53.822, Dec -72:08:26.04.

The nearest R-band source to the IR transient is an extended or confused
object (difficult to evaluate because of the high stellar density in this
field) of core magnitude R = 19.70 +/- 0.05, which is also clearly visible on
the ESO Sky Survey J plate.  We measure its position, (J2000) RA 05:09:55.44,
Dec -72:07:58.7, with respect to 40 stars from the USNO-A2.0 catalog having
an rms error of 0.45 arcsec.  Since this object is 2.3 arcsec north of the 
infrared transient, and since the IR position was reported with an
uncertainty of 1.5 arcsec, more precise astrometry of the IR image would be 
desirable to register it with the optical and to investigate the relationship,
if any, between these objects.  It seems prudent, however, to presume that
there is no connection.

This message may be cited."
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