{
  "bibcode": "2017GCN.21236....1X",
  "body": "D. Xu (NAO/CAS), J.Z. Liu, H.B. Niu, S.G. Ma, Y. Zhang, X. Zhang, G.X. \nPu,T.Z. Yang, F.F. Song (XAO/CAS), H.B. Zhao, B. Li, G.T. Zhaori, H. Lu, \nR.Q. Hong, L.F. Hu (PMO/CAS), H.X. Feng, Z.P. Zhu, T.M. Zhang, X. Zhou, \nH.X. Feng, Z.P. Zhu (NAO/CAS), J. Mao, J.M. Bai (YNAO/CAS) report on \nbehalf of the Gravitational Wave Follow-Up Network by NAO-PMO-XAO-YNAO \nin China (GWFUNC):\n\nWe have performed tiled observations of LIGO/Virgo G288732 (LVC, GCN \n21221) using the Nanshan One-meter Wide field Telescope (NOWT) with a \nFOV of 1.3 x 1.3 deg^2, located in Xinjiang, China. Observations started \nat 18:21:44 UT and ended at 21:31:17 UT on 2017-06-08, covering a total \narea of ~337 deg^2 and with each exposure of 150s in the R-band. Data \nanalysis is still underway. We note that the Fermi/LAT error circle \n(Omodei et al., GCN 21227) was not covered in the tiled observations, \nbecause the LAT altitude was too low since the starting of the observations.\n\nHowever, the NOWT manged to image the Fermi/LAT error circle at the very \nbeginning of the following night, and we obtained 3x150s and 2x200s \nR-band images around 15:30:19 UT on 2017-06-09. Five uncatalogued X-ray \nsources by Swift/XRT have been reported, which might be the X-ray \ncounterpart candidates of the Fermi/LAT transient (Evans et al. GCN \n21233). These five sources, i.e., sources #1, 2, 3, 6, and 7, are within \nthe FOV of each Nanshan exposure. Comparison with DSS-II, SDSS, and \nPanSTARRS reveals that sources #1, 3, 6, and 7 have known optical \ncounterparts already, and no apparent strong variation in brightness for \nthe optical counterparts. Source #2 doesn't have any optical counterpart \nin the DSS-II, SDSS, and PanSTARRS surveys. No optical transient is \ndetected at the source #2 position in the Nanshan images, down to a \nlimiting magnitude of R>19.2 mag. Therefore, deeper photometry at this \nposition is encouraged.",
  "circularId": 21236,
  "createdOn": 1497029693000,
  "email": "dxu@nao.cas.cn",
  "subject": "LIGO/Virgo G288732: GWFUNC/NOWT observations of the skymap and follow-up of the Fermi/LAT candidate",
  "submitter": "Dong Xu at NAO/CAS  <dxu@nao.cas.cn>",
  "eventId": "LIGO/Virgo G288732"
}