GCN Circular 6353
Subject
LT monitoring of GRB070412
Date
2007-04-27T11:54:45Z (18 years ago)
From
Evert Rol at U.Leicester <er45@star.le.ac.uk>
E. Rol, N. Tanvir (U. of Leicester), R. Smith (Liverpool JMU), report
for a larger collaboration:
We have observed the field of GRB070412 (Romano, GCN Circ. 6273) in r'
and i' bands with the 2m Liverpool Telescope at several epochs. At the
position of the X-ray afterglow (Romano, GCN Circ. 6282), we do not
detect any new sources. Our photometry is calibrated relative to the
SDSS (Adelman-McCarthy et al., 2007 ApJS in press), and our limiting
magnitudes at the observed epochs are as follows:
UT start days post T0 exptime filter lim. mag
(2007) (mid-epoch) (sec) (5-sigma)
04-12T03:13:03 0.077 600 r' 22.5
04-12T04:07:56 0.115 600 i' 21.9
04-12T04:31:59 0.132 600 r' 22.4
04-12T21:33:59 0.849 1800 r' 22.6
04-13T01:48:36 1.026 1350 i' 21.6
04-13T03:32:13 1.098 1800 r' 23.4
04-13T04:06:36 1.122 900 i' 20.7
04-15T01:11:04 3.000 1800 r' 23.7
04-15T01:50:38 3.012 1800 i' 23.2
04-25T21:34:13 13.85 1800 r' 22.3 *
04-25T22:08:19 13.87 1800 i' 22.2 *
* observations are affected by contamination from the nearby moon
Since the upper limits indicate no apparent supernova at the X-ray
position, the GRB position is either a chance coincidence with the
nearby bright galaxy (CGCG 215-024; see also Ofek, GCN Circ. 6275), or
belongs to the newly suggested class of long-duration GRBs that show
no associated supernovae (Fynbo et al. 2006, Nature 444, 1047; Della
Valle et al. 2006, Nature 444, 1050; Gal-Yam et al. 2006, Nature 444,
1053). For comparison, the expected magnitudes at 13.9 days for a
SN1998bw-like supernova at the redshift of the galaxy (z=0.0307), are
r' = 17.3 and i' = 17.6.