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GCN Circular 21236

LIGO/Virgo G288732: GWFUNC/NOWT observations of the skymap and follow-up of the Fermi/LAT candidate
2017-06-09T17:34:53Z (7 years ago)
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.
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