TITLE:   GCN CIRCULAR
NUMBER:  11616
SUBJECT: GRB 101112A: Maidanak and CrAO optical observations
DATE:    11/01/28 22:36:09 GMT
FROM:    Alina Volnova at SAI MSU  <alinusss@gmail.com>

GRB 101112A: Maidanak and CrAO optical observations

A. Volnova (SAI MSU), A. Pozanenko (IKI), �. Ezhkova (SAI MSU), �M.
Ibrahimov (MAO), V. Rumyantsev (CrAO), K. Antoniuk (CrAO), B. Satovski
(Astrotel) report on behalf of �larger GRB �follow-up collaboration:

We observed the field of the INTEGRAL GRB 101112A (Gotz et al., GCN
11396) with AZT-22 telescope of �MAO observatory in R-band on Nov.13
between (UT) 13:37:57 - 14:10:56 (Pozanenko et al, GCN 11402) and
Nov.14 between (UT) 14:42:43 - 15:15:49 under
good weather conditions and seeing ~0.9". �Both observational
sequences consist of 6 images with exposure of 300 seconds.
Additionally �we �observed the field �with �AZT-11 telescope of CrAO
in R-band on Nov.13 between (UT) 16:07:10 - 16:52:23.

Near the position of the optical afterglow (Guidorzi et al.GCN 11397,
A. de Ugarte Postigo et al. GCN 11398) there are two bright stars.
They are not separated on DSS and are included in USNO-B1.0 like a
single source USNO-B1.0 1293-0343482 (R = 18.77). In our images the
stars is well separated at the distance 2.7" between them.

The afterglow is in the wing of the southern star. �The star has the
magnitude R = 19.2 +/- 0.08 and coordinates (J2000) RA = 19:28:54.947,
Dec
= +39:21:12.29 �with position uncertainty of 0.15 arcsec. �After
subtraction of a PSF-like profile of the star from stacked image of
Nov.13 in the XRT error circle (Evans et al., GCN 11399) we found a
faint source in coordinates (J2000) RA = 19:28:54.856, Dec =
+39:21:10.67 �with position uncertainty of 0.2 arcsec. This position
is in agreement with afterglow coordinates reported by Guidorzi et al.
(GCN 11397). The distance between southern star and optical afterglow
is ~ 1.9". Using the same procedure we do not detect the afterglow on
Nov.14 �up to 22.5m.

The photometry of the sources based on several field stars from USNO-B1.0:

t-t0 (d), filter tstart �exp.,s ,d OT � �uplim(3 sigma) telescope

0.65558 R �13:37:57 �6*300 �22.2+/-0.20 �22.5 � � �AZT-22

0.76346 R �16:07:10 15*180 �n/d � � � � � � 21.1 � � �AZT-11

1.70060 R �14:42:43 �6*300 � n/d � � � � � � 22.5 � � �AZT-22

Taken together all published photometry of the afterglow (Guidorzi et
al.GCN 11397, Fatkhullin et al. GCN 11419) �we obtained light curve
which can be fairly well described by single power law with
alpha=-1.08.
The finding chart as well as light curve of the GRB 101112A can be
found at http://grb.rssi.ru/GRB101112A/