GCN Circular 668
Subject
GRB000508B, optical photometry
Date
2000-05-10T22:57:10Z (25 years ago)
From
Krzysztof Z. Stanek at CfA <kstanek@cfa.harvard.edu>
K. Z. Stanek (CfA), P. M. Garnavich (Notre Dame), P. J. Groot, S. Jha
(CfA) and M. Hicks (JPL) report:
We have observed most of the RXTE/ASM-IPN error-box of GRB 000508B
(GCN 665) using the FLWO 1.2-meter telescope on Mt. Hopkins and the
KPNO 2.1m telescope. The center of the GRB 000508B error-box is
located at Galactic coordinates (l,b)=(0.48 deg,14.38 deg), and the
Schlegel et al. (1998) Galactic reddening toward this direction is
E(B-V)=0.51 (A_V=1.7 mag). Due to the proximity to the Galactic plane
the stellar field is fairly dense.
At KPNO we obtained four 600 sec R-band images, the first two at UT
May 10 07:30 and the second two at UT May 10 11:33. At FLWO we
obtained two 600 sec R-band images, first one at UT May 10 06:39 and
the second one at UT May 10 09:14. In addition, at FLWO we have
obtained UBVI images for the field. Using DAOPHOT-II (Stetson 1992) on
the FLWO 1.2-meter R-band image we detect about 5,000 objects with
R<22.5 in 11x11 arcmin field.
Visual comparison with the POSS-II red plate reveals no obvious
``new'' objects. Employing the image subtraction code ISIS-2 (Alard
1999) between the two epochs taken at each telescope reveals four
possible variable objects located in the error-box, with the following
coordinates and magnitudes from Henden et al. (GCN 667):
V1) RA=253.58616 DEC=-20.41683 V=16.75
V2) RA=253.54913 DEC=-20.46479 V=17.33
V3) RA=253.53600 DEC=-20.43531 V=17.72
V4) RA=253.60865 DEC=-20.42111 V=18.24
All of these objects are easily identified on the POSS-II plate, so
most likely NONE of these objects is the optical counterpart to GRB
000508B. Further observations are planned at FLWO.
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