TITLE:   GCN CIRCULAR
NUMBER:  19561
SUBJECT: GRB 160623A: Mondy optical observations
DATE:    16/06/24 11:59:19 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

A. Pozanenko (IKI), E. Mazaeva (IKI),  P. Minaev (IKI), E. Klunko 
(ISTP), A. Volnova (IKI),  I. Korobtsev (ISTP),  report on behalf of 
larger GRB follow-up collaboration:

We observed the field of the bright hard GRB 160623A initially reported 
by GBM and LAT (Vianello et al., GCN 19553; Mailyan et al., GCN 19555) 
and also observed by  Konus-Wind (Frederiks  et al., GCN 19554) and 
SPI-ACS/INTEGRAL  with AZT-33IK telescope of Sayan observatory (Mondy) 
starting on June, 23 (UT) 18:21:25.  We obtained several images in 
R-filter under good weather conditions and FWHM of about 1.6 arcsec.  At 
the edge of XRT error circle  (Mingo et al., GCN 19558) we detect a 
source which is not presented in USNO-B1.0 and not visible in  POSS2 
(any filter).  Coordinates of the source are (J2000) 21:01:11.57 
+42:13:15.8 with uncertainty of 0.7 arcsec. Preliminary photometry   is 
following

t-T0    Filter  Exp.   OT(?) Err
(mid, days)     (s)

0.56330  R      20*60  19.94 0.07
0.57720  R      20*60  19.94 0.07
0.59112  R      20*60  20.32 0.13

Photometry is based on nearby USNO-B1.0 star
USNO-B.1_id  R2
1322-0479855 15.22

Despite a hint of some decaying of the source it is unclear whether 
source is an afterglow of GRB 160623A.

A finding chart can be found in 
http://grb.rssi.ru/GRB160623A/GRB160623A_160623_Mondy.png
A light curve of SPI-ACS/INTEGRAL  can be found in 
http://grb.rssi.ru/GRB160623A/GRB160623A_spi-acs.png