TITLE:   GCN CIRCULAR
NUMBER:  20700
SUBJECT: LIGO/Virgo G274296: CNEOST imaging coverage and an optical transient
DATE:    17/02/19 14:26:03 GMT
FROM:    Jinzhong Liu at Xinjiang Astronomical Observatory  <liujinzh@xao.ac.cn>

B. Li (PMO/CAS), D. Xu (NAO/CAS), H.B. Zhao, G.T. Zhaori, H. Lu, R.Q.
Hong, L.F. Hu (PMO/CAS), T.M. Zhang, X. Zhou, H.X. Feng, Z.P. Zhu
(NAO/CAS), J.Z. Liu, H.B. Niu, Y. Zhang, X. Zhang, G.X. Pu, S.G. Ma,T.Z.
Yang, F.F. Song (XAO/CAS), J. Mao, J.M. Bai (YNAO/CAS)  report on behalf
of the Gravitational Wave Follow-Up Network by NAO-PMO-XAO-YNAO in China
(GWFUNC):

We have performed tiled observations of LIGO/Virgo G274296 (LVC, GCN
20689) using the 1-m Chinese Near Earth Object Survey Telescope (CNEOST)
at Xuyi, Jiangsu, and the 0.6/0.9-m Schmidt telescope at Xinglong,
Hebei, China.

CNEOST has a FOV of 3.0x3.0 deg^2, and covered ~1400 square degrees from
10:40:00.05 UT to 22:01:49.81 UT on 2017-02-18 in the Sloan r-filter.
The skymap coverage is at

https://dl.dropboxusercontent.com/u/3665676/G274296/skymap20170218NEOST.pdf

and the typical limiting magnitude is m(r)~20.0.

Preliminary analysis from our vetting procedure reveals several
supernova (SN) candidates and quite a few AGN candidates.

Most SN candidates were already reported by different surveys days
before the G274296 trigger time (i.e., 06:05:55.05 UT on 2017-02-17). We
here note one SN candidate discovered after the GW trigger time, dubbed
as PTSS-17gpm and observed at 19:01:33 UT, at coordinates:

R.A. (J2000) = 11:59:59.45
Dec. (J2000) = +31:57:46.98

with m(r)~18.6. It was also discovered by the ATLAS project, dubbed as
AT 2017axh or ATLAS17bbz and discovered by on 12:48:57 on 2017-02-17.
This source is positionally coincident with the galaxy SDSS
J115959.38+315745.7, which has m(r)=19.47 and a PhotoZ=0.09+/-0.04.

Further observations are planned.