TITLE:   GCN CIRCULAR
NUMBER:  24087
SUBJECT: LIGO/Virgo S190408an: TMTS Optical Observation
DATE:    19/04/10 11:14:08 GMT
FROM:    Xiaofeng Wang at Tsinghua University  <wang_xf@mail.tsinghua.edu.cn>

Jun Mo, Wen-xiong Li, Xiao-feng Wang (THU), Xiao-Jun Jiang, Jie Zheng, Xiao-ming Zhang,Tian-meng Zhang (NAOC), Xing-han Zhang, Li-Ming Rui, Dan-feng Xiang, Zhi-hao Chen, Gao-bo Xi, Han Lin, 
Ji-cheng Zhang, Wei-li Lin, Cheng Miao (THU), Sheng-yu Yan (GU/THU), Ju-jia Zhang (YNAO), and Li-fan Wang (TAMU/PMO) report:

We conducted optical imaging observations for gravitational wave alert S190408an (Singer et al. GCN 24069) with 4 x 40 cm Tsinghua Ma-huateng Telescopes (TMTS) at Xinglong Observatory in Hebei Province, China (40.40° N, 117.58° E). Our observations started at 2019-04-09 19:37 UT and ended at 2019-04-09 20:20 UT, covering about 90% credible region of S190408an observable from Xinglong.  The total sky area scanned by the TMTS  is about 450 deg^2, with each exposure covering the field of view of about 18 deg^2. Our 3σ detection limit is ~19.5 mag for 60s explosure. The center coordinates of our observations are listed below. 
-----------         -------------
RA(hmd) DEC(dms)
22:20:04.00 +38:00:00.00
22:36:23.87 +42:00:00.00
22:38:56.48 +46:00:00.00
23:01:58.45 +46:00:00.00
22:49:02.22 +50:00:00.00
23:13:55.71 +50:00:00.00
23:38:49.20 +50:00:00.00
23:08:15.72 +54:00:00.00
23:35:28.97 +54:00:00.00
23:08:53.45 +58:00:00.00
23:39:05.05 +58:00:00.00
00:00:00.00 +62:00:00.00
00:34:04.85 +62:00:00.00
23:17:18.93 +62:00:00.00
23:51:23.79 +62:00:00.00
00:00:00.00 +66:00:00.00
00:39:20.25 +66:00:00.00
01:18:40.50 +66:00:00.00
00:00:00.00 +70:00:00.00
00:46:46.85 +70:00:00.00
01:33:33.70 +70:00:00.00
00:00:00.00 +74:00:00.00
00:58:02.84 +74:00:00.00
01:56:05.67 +74:00:00.00
01:16:57.35 +78:00:00.00
02:33:54.69 +78:00:00.00
------------      -------------
Detailed data analysis is still in progress and any interesting transients will be reported later.