TITLE: GCN CIRCULAR NUMBER: 9907 SUBJECT: GRB 090912 optical upper limit DATE: 09/09/13 10:17:51 GMT FROM: AAVSO GRB Network at AAVSO Arto Oksanen (Hankasalmi Obs., Hankasalmi, Finland) reports to the AAVSO International High Energy Network the following optical observations of the field of GRB090912 (GCN Circ. #9905, Ukwatta et al.): A. Oksanen reports an upper limit on the optical afterglow of CR=21.6, measured relative to USNO-A2.0 1500-05568008 (R=15.7). The X-ray afterglow position (Beardmore et al., GCN #9906) was observed using the 0.4-m Hankasalmi Observatory RC telescope with an SBIG STL-1001E CCD camera and clear filter. A total of 57 one-minute exposures were obtained, with the mid-point of the exposures at 2009 Sept 12 19:33 UT, approximately 3.7 hours post-burst. Two faint stars near the burst location are present in DSS2 images, but there is no transient source at the burst location to a limit of CR=21.6. A detailed report of these observations may be found at the following URL: ftp://ftp.aavso.org/grb/ArtoOksanen_GRB090912_2455087.38910_.txt A fits image is also available at ftp://ftp.aavso.org/grb/ArtoOksanen_GRB090912_2455087.38910_.fits The AAVSO thanks the Curry Foundation for its support of the AAVSO International High Energy Network.