[vsnet-grb-info 17183] GRB 151027A: Optical counterpart detection

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  18533
SUBJECT: GRB 151027A: Optical counterpart detection
DATE:    15/10/29 21:34:24 GMT
FROM:    Valentyna Golovnya at Main Astro Obs,Kyiv  <golov_v at ukr.net>

    Yu. Protsyuk (RI NAO), O. Kovalchuk (RI NAO) report: 

  
  
    
        
    
  
  
    We observed the field of the Swift GRB 151027A (Maselli et al. 
  
  
    GCN 18478) with 0.5-m telescope Mobitel KT-50 of Nikolaev observatory 
  
  
    with Alta-U9000 CCD-camera with R filter in robotic mode 
  
  
    from Oct., 28 (UTC) 20:34:16 till 20:59:59. 
  
  
    We obtained 19 unfiltered images of 60 s exposure and calculated 
  
  
    coordinates and magnitudes of all detected objects in UCAC4 system. 
  
  
    We don't detect any optical counterpart of GRB 151027A (Maselli et al. 
  
  
    GCN 18478; Zheng and Filippenko, GCN 18479) in coordinates near (J2000) 
  
  
    18 09 56 +61 21 12 up to ~17.2- 17.5 m . 
  
  
    After that we filtered all images and detected optical 
  
  
    counterpart in 6 images in coordinates (J2000) 
  
  
    18 09 56.680 (SD=0.s081) +61 21 12.08 (SD=0."63) 
  
  
    with brightness near 18.3m (SD=0.3m)