D. Malesani (DARK/NBI), H. Dahle, I. Skorbakk (ITA, Oslo), E. Wuyts
(Univ. Chicago), P. Jakobsson (Univ. Iceland), J. P. U. Fynbo, J. Hjorth
(DARK/NBI), report on behalf of a larger collaboration:
We observed the field of GRB 090423 (Krimm et al., GCN 9198) with the
Nordic Optical Telescope equipped with the MOSCA camera. Observations
were carried out using the SDSS z' filter, starting on Apr 23.874 UT
(13.0 hr after the GRB trigger) and with a total exposure time of 1 hr.
At the position of the NIR candidate afterglow (Tanvir et al., GCN 9202;
Levan et al., GCN 9206; Cucchiara et al., GCN 9209), we do not detect
any source down to a limiting magnitude z(AB) > 23.7, calibrated using
the SDSS catalog.
We acknowledge excellent support from the NOT visiting observers.