GCN Circular 3262
Subject
GRB 050408: RTT150 optical observations
Date
2005-04-14T07:29:26Z (20 years ago)
From
Irek Khamitov at TUG <irekk@tug.tug.tubitak.gov.tr>
I. Bikmaev, N. Sakhibullin (KSU/AST), Z. Aslan, I. Khamitov (TUG),
U. Kiziloglu (METU), A. Alpar (SabUni), R. Burenin, M. Pavlinsky,
R. Sunyaev (IKI), report:
We have observed OT of GRB 050408 (A. de Ugarte Postigo et al., GCN
3192) with Rc-filter and ANDOR CCD at the Russian-Turkish 1.5-m telescope
(RTT150, Bakyrlytepe, Turkey). We have made a set of 30 exposures with
5 min duration each during UT 18:30 - 20:10 , April 13. The weather was
clear with average seeing of 1.8 arcsec.
We have marginaly detected the OT at the limit of co-added frame with
Rc = 23.7 +/-0.2 mag.
We have re-reduced our previous observations (Aslan et al, GCN 3198)
by using Landolt standard stars.
RTT150 photometry of OT is given below:
t-t0 (hours) Rc err exposure
midtime (sec)
3.72 21.01 0.07 900 (30*30s)
4.37 21.10 0.05 1080 (18*60s)
4.89 21.25 0.05 960 (16*60s)
5.39 21.27 0.05 960 (16*60s)
5.79 21.44 0.06 960 (16*60s)
6.55 21.37 0.06 720 (12*60s)
6.85 21.50 0.06 720 (12*60s)
8.24 21.64 0.07 1200 (20*60s)
8.75 21.60 0.07 1200 (20*60s)
123.78 23.7 0.2 9000 (30*300s)
The power law decay index between 3.7h and 8.7h calculated on the
basis of the RTT150 data in Rc-band is -0.68+/-0.06 and the newly
obtained value of Rc = 23.7 shows that the lightcurve is still fit by a
single power law of -0.7 (GCN 3215, GCN 3222, GCN 3254).
RTT150 optical light curve of OT GRB050408 is shown at
http://www.tug.tubitak.gov.tr/~irekk/grb/grb050408/lc.jpg
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