A.O. Jaunsen (Univ. Oslo), J. Gorosabel (IAA-CSIC), J.P.U. Fynbo, D.
Malesani, J. Sollerman, Ch. Gall (DARK), T. Morel (Leuven), M.D.
Stritzinger (DARK), A. Somero, J. Telting, C. Villforth (NOT), report on
behalf of a larger collaboration:
We observed the field of GRB 070920A (Grupe et al., GCN #6805) in the R
band with the Nordic Optical Telescope on 2007 September 20.209-20.221
UT (1.0-1.3 hr after the GRB). Comparison images were taken on
September 20.216 and again on October 15.135 UT with the same
telescope, instrumentation and filter. Our images cover 96% of the
revised BAT error circle(Barbier et al., GCN #6807), missing a small
region at the northern boundary.
At a mean time of 1.15 hr after the GRB, we do not detect any
variable object brighter than R=24.3 (calibrated against USNO-B1.0, R1
magnitudes). There is no evidence for an associated SN on Oct. 15 down
to the same limit.