[vsnet-grb-info 5097] GRB070917: Confirmation of optical afterglow

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  6803
SUBJECT: GRB070917: Confirmation of optical afterglow
DATE:    07/09/19 19:12:30 GMT
FROM:    Johan U. Fynbo at U.Copenhagen  <jfynbo at astro.ku.dk>

J.P.U. Fynbo, M.D. Stritzinger, C. Gall (DARK/NBI), A.O. Jaunsen (Univ.
Oslo), C.C. Thoene, D. Malesani, P. Vreeswijk, J. Hjorth (DARK/NBI), J.
Sollerman (DARK and Univ. Stockholm) report on behalf of a larger
collaboration.

We observed the optical afterglow of GRB 070917 (Cummings et al., GCN
6791; Cenko, GCN 6800) with the Nordic Optical Telescope. Observations
started on 2007 Sep. 17.89 UT (14 hr after the GRB) in the V, R and I
bands. We detect the candidate optical afterglow reported by Cenko (GCN
6800) in all three bands. Assuming R=18.1 for the star USNO0900_15777166
we derive an R-band magnitude of 23.1. Compared to the magnitudes reported
by Cenko (GCN 6800) the source appears to be fading and we hence confirm
this source as the likely optical afterglow of GRB 070917.