D. Xu, G. Leloudas, D. Malesani, J.P.U. Fynbo (DARK/NBI), P. Jakobsson
(Univ. of Iceland), and G. Furesz (CfA/Harvard) report on a larger
We observed the field of GRB 090809 (Markwardt et al., GCN 9754) with
the Nordic Optical Telescope equipped with ALFOSC. We obtained 3x300 s
I-band frames, starting on August 9th, 21:49:10 UT, 4.29889 hr after the
burst; and 1x300 s R-band frame, starting 5.29861 hr after the burst.
We confirm the presence of the UVOT source (Markwardt et al., GCN 9754)
RA(J2000) = 21:54:43.17
Dec(J2000) = -00:05:01.9
which are consistent with the UVOT position. We note that the source is
not visible in the archival SDSS frames of this field, thereby proving
that it is the optical afterglow of GRB 090809.
The afterglow is detected in each I-band and R-band frame. The
preliminary magnitudes are I~19.9 and R~20.3 respectively, against the
same reference star, 0899-0602834 in the USNO B1 catalog.
Further photometric observations are underway. We encourage