[vsnet-grb-info 7646] GRB 090423: P60 Observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  9201
SUBJECT: GRB 090423: P60 Observations
DATE:    09/04/23 09:46:20 GMT
FROM:    S. Bradley Cenko at Caltech  <cenko at srl.caltech.edu>

S. B. Cenko (UC Berkeley) reports on behalf of a larger collaboration:

We have imaged the field of GRB090423 (GCN 9198, Krimm et al.) with the
automated Palomar 60-inch telescope beginning at 2009 23 April 7:58 UT (~
3 minutes after the burst) in the Sloan r', i', and z' filters.  In
coadded images we find no sources inside the XRT error circle to the
following limiting magnitudes (calculated with respect to several SDSS
stars in the field):

Mean UT		t_b (min)	Filter		Magnitude
---------------------------------------------------------------------
23 Apr 08:11	16		r'		> 21.5
23 Apr 08:15	20		i'		> 21.5
23 Apr 08:17	22		z'		> 20.5

The lack of an optical afterglow, together with the fact that the X-ray
column density is consistent with the Galactic value (Krimm et al., GCN
9198), make GRB090423 an interesting candidate high-redshift event.  We
encourage observations at longer wavelengths to search for a NIR
counterpart.