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GCN Circular 9487

GRB 090530: RTT150 Optical Observation
2009-06-03T17:47:25Z (15 years ago)
Solen Balman at METU <>
S. Balman (METU), M. Parmaksizoglu (TUG)
Z. Eker (TUG), U. Kiziloglu (METU), E. Gogus (Sabanci Uni.)
I. Bikmaev, N. Sakhibullin (KSU/AST)
R. Burenin, M. Pavlinsky, R. Sunyaev (IKI),


We observed the field of GRB 090530 (Swift trigger=353567, 
Cannizzo et al.,2009 GCN Circ. 9438) with the Russian-Turkish 1.5-m telescope
(RTT150, Bakirlitepe, TUBITAK National Observatory, Turkey) on
30 May  starting at 18:30:37.7 UT about 15.2 hours (0.633 d) after the burst 
using the TFOSC CCD (burst detected at 03:18:18 UT with Swift Burst Alert 

Flewelling et al. 2009 GCN Circ. 9439 found the afterglow at
16.0 mag at 03:18:42.7 UT. Calibrating the data against the USNO star at
RA = 11:57:41.7, Dec = +26:35:43, Rossi et al. 2009 GCN Circ. 9458
obtain R = (22.2 +-0.2) mag 21.3 hrs after burst. They also found a
  break in the optical light at around 22 ksec post-burst (see also 
GCN Circ.9440-9443, 9450-9452, 959, 9466, 9478 for white light
and UV photometry).

We obtained one 900 sec exposure using the  R band  filter (Bessell filter).
We used the Swift XRT position derived by Breadmore at al. (2009) 
GCN Circ. 9445 to locate the afterglow candidate. We were able see the 
source, but unable to calculate a magnitude using PSF photometry with
DAOPHOT within MIDAS software performed on the 13.3 by 13.3 arcmin field 
around the candidate. We find a frame upper limit of R = 21.1+/-0.5 mag
at 3 sigma and 21.9+/-0.5 mag at 2 sigma confidence level 
calculated using the same  USNO star mentioned in the above paragraph.

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