GCN Circular 1866
Subject
GRB 030131: marginal optical detection
Date
2003-02-13T15:25:33Z (21 years ago)
From
Javier Gorosabel at LAEFF-INTA, Madrid <jgu@laeff.esa.es>
J. Gorosabel (IAA-CSIC/STScI), A. Levan (U. Leicester/STScI),
A. Fruchter, J. Rhoads, J.M. Castro Cer�n (STScI), T. Tripp (Princeton)
report for a larger collaboration:
We have imaged the optical candidate (GCN 1857) of the INTEGRAL burst GRB
030131 (GCN 1836, GCN 1838, GCN 1847) with the 4-m KPNO telescope (equipped
with Mosaic, FOV=36'x36'). The observations were carried out on Feb
1.526-1.542 UT 2003 (~29 hours after the GRB) with a total exposure time of
4x500s and a seeing of 0.85".
We find a marginal detection (~3.5 sigma above the detection threshold) at
RA(J2000)=13:28:22.27 DEC(J2000)=30:40:23.7. The astrometry is based on
the USNO catalog and shows an internal uncertainty of 0.5" for each
coordinate. We have compared the offset of the object in our image from the
nearest USNO star with that found by D. Fox (personal communication) in
their discovery image. These offsets agree within 0.2", further
strengthening the association.
Preliminary aperture photometry centered on the object yields B=25.4+/-0.3.
Our photometric calibration is based on 11 USNO stars in the field. Under
the zero point obtained the star located at RA(J200)=13:28:18.16
DEC(J2000)=30:38:20.79 has B=18.18.
A smoothed image of the field can be seen at:
http://www.stsci.edu/~fruchter/GRB/030131/kpno/grb030131.kpno.gif
We thank D. Fox for providing valuable astrometric information.
