Columbia University Astronomy and 

MDM Observatory GRB Team

GRB 051227: Optical follow-up

GCN Circular #4405: GRB 051227: MDM Observation
J. P. Halpern & S. Tyagi (Columbia U.) report on behalf of the
MDM Observatory GRB follow-up team:

"We are observing the Swift XRT position (Beardmore et al., GCN 4402)
of GRB 051227 in the SDSS r filter with RETROCAM on the MDM 2.4m,
a medium-sized telescope on Kitt Peak, Arizona.  Beginning on
Dec. 28 03:55 UT, or 9.9 hours after the burst, our first 15 minutes
of exposure yields no detection to a limit R > 23, referenced to the
SDSS photometry in the field (Cool et al., GCN 4399)."

MDM 2.4m MDM 2.4m
(J2000) 08h 20m 58.11s, +31° 55' 31.9" [33"x33"]

GCN Circular in preparation: GRB 051227: MDM Observations
J. P. Halpern, S. Tyagi, &  N. Zimmerman (Columbia U.)
report on behalf of the MDM Observatory GRB follow-up team:

"Following our initial report (GCN 4405), we continued to observe
GRB 051227 on two nights under non-photometric conditions using
the MDM 2.4m telescope and RETROCAM imager with SDSS r' filter.
Poor conditions for the first few hours prevented detection of 
the optical transient discovered by Malesani et al. (GCN 4404,
4407, 4412) and Bloom et al. (GCN 4408), but later periods of
improved transparency and seeing resulted in the significant
measurements listed below.  Magnitudes were calibrated using stars
in the revised SDSS photometry files provided by Cool (GCN 4627),
and are consistent with the reported contemporaneous measurements
from Gemini-north by Berger & Soderberg (GCN 4410, 4414, 4419).
In addition, we note that the break in the light curve possibly
required by the (4 sigma) upper limit at 17.4 hours is consistent
with the inference of Berger & Soderberg (GCN 4419) that the light
was already dominated by the host galaxy at 39 hours.

  Date(UT)  Mid-time(UT)  t-t0(hr)  Exp(m)      r'(mag)
  Dec. 28      07:17        13.2      60     24.79 +/- 0.23
  Dec. 28      08:38        14.5      75     24.76 +/- 0.18
  Dec. 28      11:24        17.4      50    >25.1 
  Dec. 29      09:53        39.8      60     25.53 +/- 0.34     

Images are posted at

This message may be cited."

Jules Halpern
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Last Modified: February 2, 2006