TITLE:   GCN CIRCULAR
NUMBER:  24267
SUBJECT: LIGO/Virgo S190425z: Lijiang 2.4-m Telescope Follow-up Observations
DATE:    19/04/27 07:44:48 GMT
FROM:    Xiaofeng Wang at Tsinghua University  <wang_xf@mail.tsinghua.edu.cn>

Wen-xiong Li (THU), Jun-cheng Chen(WZU), Xiaofeng Wang (THU), Kai Ye (YNAO), Ju-jia Zhang(YNAO), Chuan-jun Wang(YNAO), Jian-guo Wang(YNAO), Jin-ming Bai (YNAO), Jun Mo (THU),  Kaixin Lu(YNAO) , Michael Coughlin (Caltech), Sarah Antier (APC), Tianrui Sun (PMO), Lei Hu (PMO), and Lifan Wang (TAMU/PMO) report on behalf of a larger collaboration: 

Using the Lijiang 2.4-m telescope (LJT) at Yunnan Observatory, China, we observed the two candidates 
ZTF19aarykkb and ZTF19aarzaod reported by the Zwicky Transient Facility (Kasliwal et al., GCN 24191) 
as possible electromagnetic counterparts of  the GW event S190425z (LIGO/Virgo Collaboration, GCN 24168). 
Both have now been spectroscopically identified as type II SNe (Pavana et al., GCN 24200; Perley et al., 
GCN 24204; Buckley et al., GCN 24205; Izzo et al., GCN 24208; Wiersema et al., GCN 24209; Nicholl et al., 
GCN 24211). Multiple images were obtained with the LJT for these two SNe in g and r bands. Using the 
Pan-STARRS Survey images as templates for image subtraction, the results of PSF photometry for them 
are listed as

UT time:                       filter       mag(error)
-------------------------------------------------------
ZTF19aarykkb:
2019-04-25T17:56:45    g       19.14+-0.07
2019-04-25T17:58:07    r        18.36+-0.06
2019-04-25T20:57:24    g       19.04+-0.06
2019-04-25T20:58:56    r        18.50+-0.05
-------------------------------------------------------
ZTF19aarzaod:
2019-04-25T21:06:56    r        19.93+-0.12

These magnitudes are consistent with previous reports (Hiramatsu et al., GCN 24194; Tan et al., 
GCN 24193; Burke et al. GCN 24206; Kilpatrick et al. 24212; Sun et al. GCN 24234), and also 
consistent with the luminsoity of SNe II at a distance of about 110 Mpc after taking into the extinctions.