TITLE: GCN GRB OBSERVATION REPORT NUMBER: 2481 SUBJECT: GRB 031203: Optical/IR Astrometry DATE: 03/12/06 17:25:12 GMT FROM: Josh Bloom at Harvard/CFA ---------- Forwarded message ---------- Date: Fri, 5 Dec 2003 23:45:21 -0500 (EST) From: Joshua Bloom To: gcncirc@lheawww.gsfc.nasa.gov Cc: scott@milkyway.gsfc.nasa.gov Subject: GRB 031203: Optical/IR Astrometry GRB 031203: Optical/IR Astrometry J. S. Bloom, C. Bailyn, M. Buxton, B. Cobb, P. van Dokkum (Yale) and D. Gonzalez (CTIO), part of the larger SMARTS consortium, report: "The position of the radio source in the XMM error box (Frail, priv. communication) is 0.43" E and 0.80" N from the bright source noted in Hsia et al. (GCN #2470). However, as explained in Bloom et al. (GCN #2472) that source itself is unlikely to be the afterglow since it was present in the DSS-II and did not vary significantly in the first night. Additional data obtained between Dec. 5 UT=5:43 and UT=7:19 showed the source at the same I-band flux as on Dec. 4 to within 0.05 mag. On both Dec. 4 and Dec. 5 the source is slightly but clearly elongated in ~1" seeing. The source-radio offset of 0.91" is larger than the formal joint 1 sigma uncertainty between the IR and the radio positional tie. It is still unclear whether this bright source is the low redshift host of the GRB or a foreground galaxy. Separately, we note that inspection of the J-band ANDICAM imaging reported in the Bailyn et al. (GCN #2463) reveals a faint (J ~ 20) source at: RA: 08:02:30.36 DEC: -39:51:00.1 (J2000) rms uncertainty relative to ICRF= 0.3 arcsec in RA and DEC" This is consistent with the XMM (#1) position. A finding chart may be found at: http://www-cfa.harvard.edu/~jbloom/grb031203 This message may be cited. [original submit time at top of header]