[vsnet-grb-info 6864] GRB 081024B: BTA deep optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  8456
SUBJECT: GRB 081024B: BTA deep optical observations
DATE:    08/11/01 10:35:39 GMT
FROM:    Vladimir Sokolov at SAO RAS  <sokolov at sao.ru>

T. Fatkhullin, A. Moskvitin (SAO-RAS Niznij Arkhyz), A.J. Castro-Tirado
(IAA-CSIC Granada), on behalf of a larger collaboration, report:


"We observed the field of the short duration GRB081024B (Omodei, GCNC 
8407; Connaughton and Briggs, GCNC 8408) in the Rc-band with the 6-m
telescope of the SAO RAS in Caucasus. In total two runs were performed
starting on 28 Oct 2008 (20:16 UT) and 29 Oct. 2008 (15:22 UT).
Integration times were 24 and 14 min respectively. Using SExtractor
software (Bertin & Arnouts 1996, A&AS 117, 393) and source "O1"
(Cenko & Kasliwal GCNC 8417; Kann et al. GCNC 8423) as a reference star,
we estimated the following magnitudes of the sources within the XRT error box:

         28 Oct.                     29 Oct.
O1: Rc = 20.55 +/- 0.04      Rc = 20.55 +/- 0.04    (from GCN 8423)
O2: Rc = 22.62 +/- 0.06      Rc = 22.65 +/- 0.06    (within 3.6 arcsec aperture)
O3: Rc = 23.19 +/- 0.15      Rc = 23.18 +/- 0.10    (within 3.6 arcsec aperture)
O4: Rc = 22.46 +/- 0.06      Rc = 22.53 +/- 0.06    (within 3.6 arcsec aperture)

The second epoch image (29 Oct.) shows that extended object "O2"
as noted from Palomar 200 inch Hale telescope observations (Cenko &
Kasliwal GCNC 8417) is most likely superposition of two objects.
These objects seem also to be extended in our image.
we conclude that all four sources showed no variability during the
time interval covered by our observations (including source "O2", whose
magnitude is comparable to the one reported by Cenko & Kasliwal).
As it is already mentioned by Guidorzi et al. (GCNC 8454) by means of
Swift/XRT observations, we can not confirm that the source "O2"
is fading in brightness, i.e. its relation to GRB081024B. This second
epoch image can be retrieved via anonymous FTP:
ftp://ftp.sao.ru/pub/grb/GRB081024B/GRB081024B_BTA_2nd_epoch.jpg ."


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