TITLE:   GCN CIRCULAR
NUMBER:  2821
SUBJECT: GRB041006: RTT150 Optical Observations
DATE:    04/10/17 20:51:32 GMT
FROM:    Solen Balman at METU  <solen@astroa.physics.metu.edu.tr>

S. Balman (METU), I. Bikmaev (KSU), U. Kiziloglu, A. Baykal (METU), E. 
     Gogus, M.A. Alpar, U. Ertan (Sabanci U.),  Z. Aslan, I. Khamitov, 
     K. Uluc (TUG), N. Sakhibullin (KSU), R. Burenin, M. Pavlinsky (IKI), 
     R. Sunyaev (IKI, MPA) report :
   
      We observed the field centered on the optical afterglow (GCN 
      2765, 2766) of GRB 041006 (=H3570) discovered by HETE (GCN 2770)   
      with the TUG (TUBITAK National Observatory, Turkey) 1.5-m 
      Russian-Turkish Telescope (RTT150).  
     
      We obtained 6x180 s R band images on 2004.10.10 (3.53 d after 
      burst) starting at 01:01:48 UT, 
      and 10x180 s R band images on 2004.10.11 (4.51 d after burst) 
      starting at 00:32:34 UT, using the imaging Loral Lick3 CCD.   
       
      The seeing was 1.8" on 2004.10.10 and 1.6" on 2004.10.11.   
      
      Our 2 sigma upper limits are m_R > 22.64 (Oct 10.05) and m_R > 23.30 
      (Oct 11.03).                   
       
      We further obtained 18X600 s R band images on 2004.10.14 between 
      21:32:32 UT (8.4 d after the burst) and 01:32:18, with RTT150 using 
      the imaging ANDOR CCD. The seeing was 1.3-1.6". 
 
      We detected the source at m_R = 23.8+/-0.25 (corresponding to 2 sigma
      detection). For calibration of the R band images we 
      used the reference stars reported in GCN (2801). 
  
      An image of the field and the source location is presented at 
      (cf. GCN 2802, 2803) :
      http://astroa.physics.metu.edu.tr/grb/grb041006/grb041006_rtt150.jpg
 
      Our results in comparison with the extrapolation of the earlier 
      detections on the R band light curve are shown at : 
      http://astroa.physics.metu.edu.tr/grb/grb041006/grb041006_plot.gif                          
 
 
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