TITLE: GCN CIRCULAR NUMBER: 21236 SUBJECT: LIGO/Virgo G288732: GWFUNC/NOWT observations of the skymap and follow-up of the Fermi/LAT candidate DATE: 17/06/09 17:34:53 GMT FROM: Dong Xu at NAO/CAS D. Xu (NAO/CAS), J.Z. Liu, H.B. Niu, S.G. Ma, Y. Zhang, X. Zhang, G.X. Pu,T.Z. Yang, F.F. Song (XAO/CAS), H.B. Zhao, B. Li, G.T. Zhaori, H. Lu, R.Q. Hong, L.F. Hu (PMO/CAS), H.X. Feng, Z.P. Zhu, T.M. Zhang, X. Zhou, H.X. Feng, Z.P. Zhu (NAO/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 G288732 (LVC, GCN 21221) using the Nanshan One-meter Wide field Telescope (NOWT) with a FOV of 1.3 x 1.3 deg^2, located in Xinjiang, China. Observations started at 18:21:44 UT and ended at 21:31:17 UT on 2017-06-08, covering a total area of ~337 deg^2 and with each exposure of 150s in the R-band. Data analysis is still underway. We note that the Fermi/LAT error circle (Omodei et al., GCN 21227) was not covered in the tiled observations, because the LAT altitude was too low since the starting of the observations. However, the NOWT manged to image the Fermi/LAT error circle at the very beginning of the following night, and we obtained 3x150s and 2x200s R-band images around 15:30:19 UT on 2017-06-09. Five uncatalogued X-ray sources by Swift/XRT have been reported, which might be the X-ray counterpart candidates of the Fermi/LAT transient (Evans et al. GCN 21233). These five sources, i.e., sources #1, 2, 3, 6, and 7, are within the FOV of each Nanshan exposure. Comparison with DSS-II, SDSS, and PanSTARRS reveals that sources #1, 3, 6, and 7 have known optical counterparts already, and no apparent strong variation in brightness for the optical counterparts. Source #2 doesn't have any optical counterpart in the DSS-II, SDSS, and PanSTARRS surveys. No optical transient is detected at the source #2 position in the Nanshan images, down to a limiting magnitude of R>19.2 mag. Therefore, deeper photometry at this position is encouraged.