TITLE: GCN GRB OBSERVATION REPORT NUMBER: 1904 SUBJECT: GRB 030227, possible optical counterpart of XMM-Newton source DATE: 03/02/28 00:29:35 GMT FROM: Alberto Castro-Tirado at LAEFF-INTA A.J. Castro-Tirado, D. Reverte, J. Vílchez (IAA-CSIC), J. Gorosabel (IAA-CSIC/STScI), J. M. Castro Cerón (STScI), A. de Ugarte and S. Guziy (IAA-CSIC) report: "We have imaged a 30' x 30' region centred on the INTEGRAL error box for GRB 020327 (Gotz et al. GCN Circ. 1895, 1896) with the 2.5-m Isaac Newton telescope at Observatorio del Roque de los Muchachos (Canary Islands, Spain). One B-band frame and one R-band frame (600-s exposure time each) were obtained on Feb 27.872 UT (i.e. 12.2 hours after the GRB) under good meteorological conditions. Within the X-ray source error box given by XMM-Newton (Loiseau et al. GCN Circ. 1901) we find a point-like object (R = 22.5 preliminarly) which is also marginally detected in the B-band frame. Coordinates yield AR(2000) = 04 57 33.05, Dec(2000) = +20 29 03.5 (preliminary, +/- 1"). Further observations are needed to confirm whether this object is the optical afterglow to GRB 030227. The object reported by Ofek and Gal-Yam (GCN Circ. 1903) is also detected in our images with R about 21.5. An image of the field is posted at: www.iaa.csic.es/~ajct/GRBs/grb030227." This message can be quoted.