|GCN Circular #4381
Possible GRB 051221B: MDM Detection
J. P. Halpern & S. Tyagi (Columbia U.) report: "We observed the position of possible Swift GRB 051221B in the R-band with the MDM 1.3m for 30 minutes starting on Dec. 22 01:31 UT, or 5.5 hours after the BAT trigger (Boyd et al., GCN 4376). We find an object of R=21.8 located at RA(J2000) = 20h 49m 34.8s Dec(J2000) = +53d 02' 11.8" which is consistent in position with the fading XRT source (Page et al., GCN 4378). (We use a USNO B1.0 comparison star at 20h 49m 36.08s, +53d 01' 29.65".) We have not established any optical variability at this time."
|MDM 1.3m - 2005 Dec 22 01:31 UT|
|Halpern & Tyagi (GCN 4381)|
|Maidanak 1.5m - 2005 Dec 22 15:41 UT|
|Sharapov et al. (GCN 4612)|
|Possible GRB 051221B|
|(J2000) 20h 49m 35.1s, +53° 02' 12.2"|
|GCN Circular #4614
Possible GRB 051221B: MDM Correction
"I revise here the report in GCN 4381 of an optical object at the Swift XRT position of the possible GRB 051221B (Boyd et al. GCN 4376, Page et al. GCN 4378, Fenimore et al. GCN 4382), prompted by the non-detections at this position by Milne (GCN 4420) and Sharapov et al. (GCN 4612). The position and magnitude given in GCN 4381 were both in error as a result of using an incorrect entry in the USNO-B1.0 catalog for the quoted comparison star. The only object that is consistent in position, within 4.5", of the fading XRT source (Page et al. GCN 4378), is located at RA(J2000) = 20h 49m 34.86s Dec(J2000) = +53d 02' 08.3" It is also faintly visible on the digitized R and I-band POSS-II plates, and clearly on the image of Sharapov et al. Since it was not ruled out that this event was a hard X-ray transient, it is still possible to test that hypothesis by searching for an optical counterpart. However, there is no evidence in MDM images that the above object has varied. Observations of it from from 5.5 to 8 hours after the event using the MDM 1.3m, and again at 30.6 hours using the MDM 2.4m, are all consistent with its appearance on the POSS, and with measurement on the CCD images of R = 20.63+/-0.03, referenced to a USNO B1.0 star at 20h 49m 36.16s, +53d 01' 26.4" having R2 = 17.54. The MDM 2.4m image further sets a limit of R > 23.8 on any other object in the XRT error circle, and is shown here: http://www.astro.columbia.edu/~jules/grb/051221b Recall that Galactic extinction in this direction, (l,b) = (91.2,+5.8), is considerable. E(B-V) = 1.37 mag, corresponding to A_R = 3.66 mag (Schlegel et al. 1998). This message may be cited."
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