TITLE:   GCN CIRCULAR
NUMBER:  21898
SUBJECT: LIGO/Virgo G298048: SSS17a photometry of CHILESCOPE observatory
DATE:    17/09/19 18:09:03 GMT
FROM:    Alexei Pozanenko at IKI,Moscow  <grbgw.iki@gmail.com>

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

We report a photometry  of  the counterpart SSS17a/DLT17ck (Coulter et 
al. GCN 21529;  Yang et al., GCN 21531) of LIGO/Virgo trigger G298048 
(LIGO Scientific Collaboration and Virgo Collaboration, GCNs 21509, 
21513)  with RC-1000 1m telescope of CHILESCOPE observatory (GCNs 21618, 
21635, 21644). The observations carried out in a clear filter in four 
epochs. We used last epoch (7.49278 days after trigger)  to construct a 
mask for subsequent mask subtraction. The PSF photometry is based on 
several nearby USNO-B1.0 stars (R2 magnitudes).

Photometry of the transient SSS17a/DLT17ck is following


Date       UT start   t-T0    Filter Exp.    OT     Err.
                       (mid, days)     (s)

2017-08-19 23:30:33  2.46157  CR     10*180  19.12  0.06
2017-08-20 23:21:09  3.47840  CR     13*180  20.04  0.08
2017-08-21 23:32:09  4.49409  CR     22*180  20.14  0.12
2017-08-24 23:53:39  7.49278  CR     20*180 >21.0 (3 sigma upper limit)