[vsnet-grb-info 9401] GRB 100621A: IRSF/SIRIUS NIR Observation

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  10881
SUBJECT: GRB 100621A: IRSF/SIRIUS NIR Observation
DATE:    10/06/22 15:37:21 GMT
FROM:    Hiroyuki Naito at Nagoya U  <naito at stelab.nagoya-u.ac.jp>

H. Naito, T. Sako, D. Suzuki, S. Kobara and K. Omori (Nagoya Univ.) on  
behalf of the MOA Collaboration,
T. Nagayama, M. Kurita (Nagoya Univ.) and N. Oi (The Graduate  
University for Advanced Studies/NAOJ)
on behalf of the IRSF Collabration report:

We searched for a NIR afterglow of GRB 100621A (Ukwatta et al., GCN  
10870) starting from
04:02 to 04:51 UT on 2010 June 21 with the SIRIUS on the IRSF 1.4m  
telescope at SAAO in
South Africa. In images of a 300 sec exposure with J, H and Ks filter,  
we detected an new source
within the error circle of the enhanced Swift XRT position (Evans et  
al., GCN 10873) and at the
location of the GROND source (Updike et al., GCN 10874) . The  
estimated magnitudes are the
followings.

---------------------------------------------------------------
Mid time from   Total Exp.   J-mag*   H-mag*   K-mag*
trigger (min)     (s)
---------------------------------------------------------------
61.41                 300              16.56      15.22      14.18
67.61                 300              16.24      14.63      13.84
73.84                 300              15.27      13.78      12.63
80.14                 300              15.07      13.57      12.40
86.36                 300              14.93      13.45      12.23
92.56                 300              14.90      13.45      12.32
98.81                 300              14.93      13.47      12.34
105.0                 300              15.04      13.55      12.36
---------------------------------------------------------------
*Typical error is ~ 0.1 mag

This photometry was done by using the DoPhot and calibrated against  
the 2MASS catalog stars,
and not corrected for the Galactic extinction. The source was  
brightened up by >1mag during our
observation period while the other field stars were reasonably stable.