Difference: GCNCIRCULAR21635 ( vs. 1)

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

We observed the possible counterpart SSS17a/DLT17ck (Coulter et al.
GCN 21529; Yang et al., GCN 21531) of LIGO/Virgo trigger G298048 (LVC
GCNs 21509, 21513) with RC-1000 telescope of CHILESCOPE observatory.
The observations carried out in clear filter in two epochs, on Aug. 19
and Aug.20.

Photometry of the transient SSS17a/DLT17ck is following

Date UT start Filter OT Err UpLim (3 sigma)

2017-08-19 23:30:33 CR 16.7 0.2 21.9
2017-08-20 23:21:09 CR 18.5 0.2 22.0

The photometry is based on several nearby USNO-B1.0 stars (R2). The photometry is still preliminary and required careful estimation of NGC4339 influence. Nevertheless it is evident the source is fading significantly which is confirmed by many observations (e.g. Im et al., GCN 21632 and references in the GCN 21632).

We are grateful for the team of remote controlled CHILESCOPE observatory (www.chilescope.com) for observations.

-- ShaonGhosh - 21 Aug 2017