TITLE:   GCN CIRCULAR
NUMBER:  25963
SUBJECT: LIGO/Virgo S190930t: Swift J221951-484240 optical photometry of Chilescope observatory
DATE:    19/10/06 18:27:57 GMT
FROM:    Alexei Pozanenko at IKI, Moscow  <apozanen@iki.rssi.ru>

S. Belkin (IKI), A. Pozanenko (IKI), M. Krugov (AFIF), E. Mazaeva (IKI), 
A. Volnova (IKI) report on behalf of IKI-FuN follow-up collaboration:

We observed  the Swift J221951-484240 blue Optical Transient (Oates et 
al., GCN 25901; Oates et al., GCN 25939)   in the field of the 
LIGO/Virgo S190930t (LIGO Scientific Collaboration and the Virgo 
Collaboration, GCN  25876). Several images were obtained in r' -filter 
of RC-1000 telescope. The OT was also previously observed by Kamei et 
al. (GCN 25941) and Buckley et al. (GCN 25962). Preliminary photometry 
of  the Swift J221951-484240 OT  is following.

Date       UT start MJD         Filter Exp.  OT    Err.  UL
                     (mid, days)        (s)

2019-10-05 04:22:44 58761.19808  r'    2700  19.35 0.06  22.7

The photometry is based on the USNO-B1.0 stars (reverse Lupton's 
transformation VRI -> r)

  USNO-B1.0_id r_Sloan(Lupton)
  0412-0779298 16.866
  0412-0779234 17.469
  0413-0785834 16.580
  0413-0785834 17.565
  0413-0785847 16.517