TITLE:   GCN GRB OBSERVATION REPORT
NUMBER:  668
SUBJECT: GRB000508B, optical photometry
DATE:    00/05/10 22:57:10 GMT
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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