TITLE:   GCN CIRCULAR
NUMBER:  21675
SUBJECT: LIGO/Virgo G298936: GWFUNC/CNEOST optical observations and an optical transient
DATE:    17/08/24 11:40:16 GMT
FROM:    Dong Xu at NAO/CAS  <dxu@nao.cas.cn>

D. Xu (NAO/CAS), B. Li, H.B. Zhao, G.T. Zhaori, H. Lu, R.Q. Hong, L.F. 
Hu (PMO/CAS), H.X. Feng, Z.P. Zhu, T.M. Zhang, X. Zhou (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 G298936 (LVC, GCN 
21656) using the 1-m Chinese Near Earth Object Survey Telescope (CNEOST) 
at Xuyi, Jiangsu, China.

CNEOST has a FOV of 3.0x3.0 deg^2, and carried out observations during 
17:46:32 - 20:45:48 UT on 2017-08-23 in the Sloan i-filter. In total, 
387 deg^2 is covered on the skymap with the highest localization 
probability in the north hemisphere. During the observations, the 
typical 5\sigma limit is ~19.8 mag.

Preliminary analysis reveals an optical transient (OT), named as 
GWFUNC-17ure, at the coordinates

RA (J2000) =     03:40:39.45
DEC (J2000) = +40:33:22.90

with m(i)~19.2 at 18:54:42 UT on 2017-08-23, apparently localized in its 
host galaxy SDSS J034039.45+403322.6 that has m(g)=20.32, m(r)=19.53, 
m(i)=19.14, as well as a PhotZ=0.12+/-0.04 (corresponding to D_L ~ 577 
+/- 200 Mpc).

Spectral observations of the above OT is encouraged.