[vsnet-grb-info 4593] LT monitoring of GRB070412

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6353
SUBJECT: LT monitoring of GRB070412
DATE:    07/04/27 11:54:45 GMT
FROM:    Evert Rol at U.Leicester  <er45 at 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.