GCN Circular 19140

Soomin Jeong (SKKU/IAA-CSIC), Myungshin Im, Changsu Choi and Gu Lim (CEOU/SNU) on behalf of a larger collaboration:


We observed the field of GRB160303A (Beardmore et al., GCN 19126
Not found
 
 
) with CQUEAN at the Otto Struve 2.1 m telescope


in McDonald Observatory, Texas. The observation started at 11:44, Mar 03 UT (i.e. 0.83 hr post burst) and the observation 

was conducted in r-, i-, R-, z- band. 



In the median combined image (5 x 120s) of i-band, a possible counterpart is detected near the centre of XRT enhanced 

position (Evans et al., GCN 19132
Not found
 
 
). We noticed that our i-band detection is slightly offset from a previously identified position 

by RATIR (Butler et al., GCN 19131
Not found
 
 
) and found another marginal detection at the RATIR detection, i.e., outskirt of XRT 

enhanced position (Evans et al., GCN 19132
Not found
 
 
).


 
Faint features are barely detected also in an 5 x 120s, r-band exposure, however the detection error is too big to reveal its reality. 

It is in relatively outskirt within XRT enhanced error circle and at the previously reported optical position (Butler et al., GCN 19131
Not found
 
 
; Emery et al., GCN 19134
Not found
 
 
). 

In comparison to other reports, the detection in i-band looks like a fading afterglow (Butler et al., GCN 19131
Not found
 
 
), and the position of

 the possible object in r-band is coincident to the previous optical detection by RATIR (Butler et al., GCN 19131
Not found
 
 
) and NOT (De Ugarte et al., GCN 19136
Not found
 
 
). 

The faint r-band source could be the host galaxy or highly contaminated counterpart from the underlying host. 


The analysis of R- and z-band images is still ongoing. 



T_mid (hr)  Exposure (s)     Filter       Magnitude (AB)


-----------------------------------------------------------------------------------

0.92               5x120               i          22.54 +/- 0.26 

1.13               5x120               r          23.06 +/- 0.41

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The fields are calibrated to a nearby star at RA=168.701176, Dec=22.745212 from SDSS.