GCN Circular 10116
Subject
GRB 091024: optical observations
Event
Date
2009-11-01T22:00:15Z (16 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Rumyantsev, V. Biryukov (CrAO), A. Pozanenko (IKI) report on behalf of
larger GRB follow-up collaboration:
We observed the field of the Swift GRB 091024 (Marshall et al., GCN 10062)
with ZTE telescope of Crimean branch of SAI MSU in R-filter on Oct.24
between (UT) 16:18:50 - 00:04:47 and Oct.25 19:07:19 - 19:48:19 under
moderate seeing of about 3". In initial images we detect fading afterglow
(Mundell et al., GCN 10063). In a combined image of the Oct. 24 the
afterglow looks like extended due to the nearby NW object reported by
Moskvitin et al. (GCN 10101).
In a preliminary data reduction we do not separate afterglow and nearby
object. The astrometry of the afterglow + nearby object is following
Oct.24
RA(J2000): 22 36 59.61
Dc(J2000): +56 53 23.1
with uncertainty of 0.5 arcsec
Oct.25
RA(J2000): 22 36 59.33
Dc(J2000): +56 53 24.5
with uncertainty of 0.5 arcsec
The coordinates of Oct. 24 consistent with afterglow coordinates (Mundell et
al., GCN 10063, Henden et al. GCN 10073, Chornock et al. GCN 10075). The
angular distance between astrometry results is 2.7" suggests a prevalence
of the afterglow on Oct.24 and nearby object on Oct.25. Taking into account
the redshift of z = 1.091 (Cucchiara et al. GCN 10065, Cenko et al. GCN
10093) one can estimate the distance between afterglow and object as 22 kpc
and the nearby object could be the host galaxy of GRB 091024 as suggested
early (Moskvitin et al. GCN 10101).
A preliminary photometry of the afterglow+nearby object is based on
reference star USNO B1.0 1468-0448529 (22 36 55.66 +56 53 04.2) assuming
R=17.30:
T0+ Filter, Exposure, mag., err.
(d) (s)
0.3210 R 600 18.31 +/-0.07
0.3283 R 600 18.56 +/-0.08
0.3356 R 600 18.72 +/-0.08
0.3429 R 600 18.56 +/-0.08
0.3522 R 600 18.73 +/-0.08
0.3595 R 600 18.80 +/-0.09
0.3668 R 600 18.89 +/-0.11
0.3741 R 600 18.70 +/-0.08
0.3814 R 600 19.20 +/-0.16
0.3887 R 600 19.16 +/-0.16
0.3960 R 600 18.86 +/-0.15
0.4076 R 780 19.44 +/-0.34
0.5706 R 1260 19.11 +/-0.08
0.5873 R 1320 19.15 +/-0.09
1.4386 R 2340 20.7 +/- 0.2
We caution that afterglow photometry above is contaminated by the nearby
object which we suggest as a candidate of host galaxy. The combined image
can be found at http://grb.rssi.ru/GRB091024/GRB091024a_091024_R_ZTE.gif
where vertical tick points out the afterglow and horizontal one points out
the nearby object.