Columbia University Astronomy and 

MDM Observatory GRB Team

Optical Afterglow of GRB 100213B

GCN Circular #10913
GRB 100213B: Detection of Fading Optical Afterglow
Y. Li, J. Weston, X. Fernandez, A. Brown, J. H. Yoon, A. P. S. Crotts,
and J. P. Halpern (Columbia U.) report on behalf of the graduate 
Observational Astronomy class:

"We obtained R-band images of the field of Swift GRB 100213B (Vetere et al.,
GCN 10412) on two consecutive, photometric nights using the MDM 1.3m telescope,
for total exposure times of 30 and 40 minutes, respectively.  Within 3.8" of
the enhanced Swift XRT afterglow position (of 90% confidence radius 3.5",
Evans (GCN 10423), we find a fading object at

       (J2000) R.A. = 08h 17m 07.94s, Decl. = +43d 26' 54.94"

with positional uncertainty ~0.5", and the following magnitudes:

     Date(UT)  Mid-time(UT) t-t0(hr)  Exp(min)      R(mag)
     Feb. 14      03:44        4.8       30      22.00+/-0.14
     Feb. 15      03:35       28.6       40      23.01+/-0.24

Magnitudes are referenced to Landolt (1992) standard stars, and are not corrected
for Galactic extinction.

The position of the afterglow coincides with the R ~ 21.5 object detected by 
Malesani et al. (GCN 10413) 19 minutes after the GRB, and whose redshift 
z = 0.604 was measured by Cucchiara et al. (GCN 10422).  We conclude that the
observed variability and positional coincidence with an emission-line object
establishes the optical afterglow and host galaxy redshift of GRB 100213B.
Further observations of the host galaxy are encouraged.

MDM images of the field are posted at

This message may be cited."

(J2000) 08h 17m 07.74s, +43° 26′ 51.8″ (XRT 3.5&Prime radius)
MDM 2.4m
GRB 100213B: MDM 1.3m R-band 2010 Feb. 14.15 UT

MDM 2.4m
GRB 100213B: MDM 1.3m R-band 2010 Feb. 15.15 UT

Yuan Li
Jules Halpern
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Last Modified: June 30, 2010