Difference: GCNCIRCULAR21754 ( vs. 1)

A. Pozanenko (IKI), A. Volnova (IKI), I. Reva (AFIF), E. Mazaeva (IKI), P. Minaev (IKI), M. Krugov (AFIF) report on behalf of IKI-GW follow-up collaboration:

We observed the field of the Optical Transient discovered by Swift/UVOT (Emery et al., GCN 21733) with Zeiss-1000 1-m telescope of Tien Shan Astronomical Observatory starting on 2017-08-28 (UT) 18:54:36. We obtained several images in R-filter. The optical transient (Emery et al., GCN 21733) is not detected in a combined image. Preliminary photometry of the afterglow is following.

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

2017-08-28 18:54:36 3.24609 R 8*180 n/d n/d 20.8

Photometry is based on nearby USNO-B1.0 stars (R2 magnitudes). The nearest galaxy (SDSS J014008.25+343414.8) to the transient position in coordinates (J2000) 01 40 08.247 +34 34 14.43 +/- 0.25" is marginally detected. The galaxy is at a distance of 11.5 arcsec from the transient position. The galaxy photometry is R=21.45 +/- 0.45.

-- ThomasKupfer - 29 Aug 2017