[vsnet-grb-info 19429] GRB 170524A: TSHAO and CrAO optical observations

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  21145
SUBJECT: GRB 170524A: TSHAO and CrAO optical observations
DATE:    17/05/25 20:28:02 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen at iki.rssi.ru>

E. Mazaeva (IKI), S. Nazarov (CrAO), A. Kusakin (Fesenkov Astrophysical 
Institute),  A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of 
larger GRB follow-up collaboration:

We observed the field of the Swift GRB 170524A (trigger=754322) (Gropp 
et al., GCN 21135)  with Zeiss-1000 (East) of Tien Shan Astronomical 
Observatory and AZT-8 telescope of CrAO. We obtained several images in R 
filter. The TSHAO observations started on 2017-05-24 (UT) 20:31:45 under 
not optimal weather conditions.  Observations in CrAO started on 
2017-05-25 (UT) 00:18:50. Within enhanced XRT position (Evans et al. GCN 
21136)  we did not detect any  optical source in the first epoch. In the 
second epoch (CrAO observation) we detected an object which is on the 
edge of the  enhanced XRT position. The object has coordinates (J2000) 
21:17:56.30 +48:36:27.9 with uncertainties of about 1 arcsec in each 
coordinate and brightness of R=20.10 +/- 0.15 at 0.1992 days after the 
Swift trigger. For now we can not say anything about the object 
variability. However the object is barely visible in DSS2 (Red).
The preliminary results of field photometry are as follows

Date       UT start   t-T0   Filter  Exp.      UL(3 sigma)
                       (mid, days)    (s)

2017-05-24 20:31:45 0.06857  R       46*120    20.3
2017-05-25 00:18:50 0.19920  R       10*180    21.5

Photometry is based on nearby USNO-B1.0 stars

USNO-B1.0_id    R2

1386-0392957 16.69

1385-0394718 17.29

1386-0392907 17.11


The finding chart of the object can be found at
http://grb.rssi.ru/GRB170524A/GRB170524A_CrAO_170524.png