[AAVSO-HEN] GRB 100212A: candidate optical afterglow

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TITLE:   GCN CIRCULAR
NUMBER:  10402
SUBJECT: GRB 100212A: candidate optical afterglow
DATE:    10/02/12 21:32:58 GMT
FROM:    Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst  <malesani at dark-cosmology.dk>

D. Malesani, G. Leloudas, J. P. U. Fynbo (DARK/NBI), D. Xu (WIS and 
DARK/NBI), P. Jakobsson (Univ. Iceland), A. Somero, S. Katajainen 
(Tuorla Obs.), T. Pursimo (NOT), report on behalf of a larger collaboration:

We observed the field of GRB 100212A (Grupe et al., GCN 10401) with the 
NOT equipped with ALFOSC. Observations started on Feb 12.841 UT (6.05 hr 
after the GRB), in the R band.

Close to the refined XRT error circle (as reported in the SPER web page 
http://www.swift.ac.uk/sper/index.php at 21:30 UT), we detect a source 
which is not visible in the DSS. Its coordinates are (J2000):

RA = 23:45:40.23
Dec = +49:29:40.7

The object is 2.5" away from the centre of the XRT position, currently 
reported to have a 2.2" error radius.

The R-band magnitude of the source is R = 20.3 assuming R = 17.3 for the 
USNO star at RA = 23:45:42.93, Dec = +49:30:29.3. The source looks 
pointlike under a seeing of 1" and is clearly brighter than other 
closeby objects visible in the DSS.

We suggest this object to be the afterglow of GRB 100212A.