|GCN Circular #4623
GRB 051211A: MDM Observations
J. P. Halpern (Columbia U.) & N. Mirabal (U. Michigan) report on behalf of the MDM Observatory GRB follow-up team: "Guidorzi et al. (GCN 4356) reported a possible optical afterglow for the HETE-2 burst GRB 051211A (Atteia et al., GCN 4324; Kawai et al., GCN 4359) that faded from R = 21.15+/-0.15 to R = 21.75+/-0.20 between 6.3 hr and 11.4 hr after the burst. As they noted that there is a hint of its presence on the I-band POSS plate, and in view of the likelihood that this was a short burst (Norris et al., GCN 4377), it is interesting to follow up on this candidate afterglow to determine if it is hosted by a relatively nearby galaxy. We observed and detected the same object on 2005 Dec. 25 with the MDM 2.4m telescope and RETROCAM imager in five 300 s exposures in the SDSS r' filter. Its position is R.A. = 06:56:09.00, Decl. = +32:40:06.3 (J2000), the same as previously determined. Calibration with Landolt stars yields R = 21.72+/-0.05 (statistical), with an additional systematic uncertainty of 0.1 likely. This is consistent with the later measurement of Guidorzi et al., but not their earlier one. The object is not resolved in our images at the seeing of 0.95", which argues against a host interpretation. We observed it again in the I band with the MDM 8K imager on 2006 Jan. 29. Three 600 s exposures were obtained in seeing of 0.85". Although the latter images are uncalibrated, the object appears not to have faded, is still at the limit of the I-band POSS plate, and is still unresolved. Therefore, we conclude that it is most likely a star and not the afterglow of GRB 051211A. The MDM I-band image is posted at http://www.astro.columbia.edu/~jules/grb/051211a/ This message may be cited."
|(J2000) 06h 56m 09.00s, +32° 40' 06.3" (1.5'x1.5')|
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