TITLE:   GCN CIRCULAR
NUMBER:  26487
SUBJECT: LIGO/Virgo S191216ap: No candidates found in CHES observations of HAWC error region
DATE:    19/12/18 17:47:27 GMT
FROM:    Tianrui Sun at Purple Mountain Obs,CAS  <trsun@pmo.ac.cn>

Tianrui Sun, Chen Zhang, Yiding Ping, Xuefeng Wu.(PMO).

We observed the corrected list of galaxies coincident with LIGO/Virgo and HAWC positions by Leo Singer (GCN 26479).

The observation used the 80cm telescope with the FOV of 2x2 deg^2 of the CHanging Event Survey at the YaoAn observation station(101.1811E, 25.528N) in Yunnan Province, China. 
Our observations started at 12:04:04UT and ends at 12:55:05UT Dec 18, 2019, with 11 exposure 60 seconds in white filter.

Our results for these galaxies:
| RA               | DEC         |  Mag(White) | SDSS(r)    |
| 323.482422 | 5.279632 |  16.42      | 16.50    |
| 323.056030 | 4.832057 |  15.94      | 15.83    |
| 322.921936 | 5.503483 |  15.70      | 15.57    |
| 322.838806 | 5.255421 |  15.60      | 15.41    |
| 322.821228 | 5.553754 |  15.64      | 15.83    |
| 323.173767 | 4.467985 |  16.09      | 16.10    |
| 322.906006 | 5.850705 |  16.69      | 16.84    |
| 323.034882 | 4.482058 |  16.27      | 16.24    |

And the observations of CHES:
Date-obs             RA       DEC    MAG   FWHM
2019-12-18T12:04:04  323.1053 5.3952 18.07 3.67 
2019-12-18T12:07:48  323.6028 6.0834 17.92 4.18 
2019-12-18T12:19:03  323.1023 6.0505 18.08 3.61 
2019-12-18T12:20:11  323.1023 6.0507 18.05 3.71 
2019-12-18T12:21:26  323.2811 4.3005 17.98 3.83 
2019-12-18T12:23:49  323.1022 6.0512 18.02 3.68 
2019-12-18T12:24:57  323.1023 6.0515 18.03 3.68 
2019-12-18T12:51:43  323.4745 5.3269 17.94 3.87 
2019-12-18T12:53:58  323.4746 5.3273 17.91 3.96
2019-12-18T12:55:05  323.4746 5.3273 17.90 3.96 
2019-12-18T12:09:03  323.7238 5.8421 17.43 5.50 

We did not detect any candidate source related to these galaxies in 5 sigma limit at 18.86 (median combined) generated from G band in  Gaia DR2.