[vsnet-grb-info 5675] GRB080205: optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  7332
SUBJECT: GRB080205: optical observations
DATE:    08/02/26 17:05:10 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

V. Rumyantsev (CrAO), V. Biryukov (SAI, MSU), E. Klunko (ISTP), M. Andreev 
(Terskol Branch of Institute of Astronomy), A.J. Castro-Tirado (IAA-CSIC), 
A. Pozanenko (IKI) on behalf of larger GRB follow up collaboration  report:

We observed the afterglow (Li at al,  GCN 7251), of GRB080205 (Palmer  et 
al, GCN7250) with 1.5m telescope of Sayan observatory (Mondy) on Feb.05 in 
BR and Feb.06; with Zeiss-600 of Mt. Terskol observatory on Feb.05 in R; and 
with CrAO Shajn 2.6m telescope in BVRI on Feb.05, and on Feb.06.  In CrAO 
observations we detected afterglow in R, V and not detected in B, I on 
Feb.05. We do not detect afterglow in any observations on Feb.06.

T0+       Exposure  R_mag (err)   UL    Site     seeing
(mean)

0.226 d  40x60 s   n/d           21.1  Mondy    2.2"
0.379 d  30x60 s   22.26 (0.19)  23.0  CrAO     1.5"
0.409 d  20x90 s   n/d           20.3  Terskol  2.0"
0.548 d  34x60 s   22.26 (0.15)  23.3  CrAO     1.4"
0.772 d  40x60 s   n/d           22.4  CrAO     1.4"
1.530  d 123x60 s   n/d           23.8  CrAO     1.7"

Preliminary photometry reduction is based on USNO-B1.0 stars.

Taking together KAIT (Li at al. GCN 7254) and ING (Rol  et al. GCN 7258) 
observations one can suggest some episodes of a light curve of the GRB080205 
afterglow: the steep decline of light curve with power law index  about -1.6 
between 537 s - 50 m (Li at al. GCN 7254), the shallow decay with power law 
index of  -0.9 between T0+ 50m - 9h,  plateau (or rebrightening) between T0+ 
9h - 13h, and after then very steep decline. The data after ~50 m after 
burst onset is also compatible with a single power law with index  -1.1 and 
a bump between   9h - 13h. Since we do not detect afterglow on Feb.06 
(R>23.8) it is most probably that the previous phases of the light curve is 
not contaminated by a host galaxy.  Our non detection of the afterglow in 
B-filter confirms the redshift less than ~4 (Oates at al.  GCN 7253,  Perley 
at al.  GCN 7254).

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