TITLE:   GCN CIRCULAR
NUMBER:  26432
SUBJECT: LIGO/Virgo S191213g: LCOGT photometry of ZTF19acymaru/AT2019wnh
DATE:    19/12/15 07:46:53 GMT
FROM:    Igor Andreoni at Caltech  <igor.andreoni@gmail.com>

Igor Andreoni (Caltech), Shreya Anand (Caltech), Mansi M. Kasliwal (Caltech), Michael M. Coughlin (Caltech) 
on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) collaboration


We used the Sinistro camera on the 1-m LCO Global Telescope Network (LCOGT, Brown et al., 2013) to observe the optical transient ZTF19acymaru/AT2019wnh (GCN #26424). The source was reported via GCN circular during the follow-up of the binary neutron star merger candidate S191213g (LVC, GCN #26402).

Images of ZTF19acymaru/AT2019wnh were acquired in g-r-i bands, with an exposure time of 180s for each image. The observations were performed under proposal ID TOM2020A-008, awarded as part of the TOM Community Development Program. The table below reports aperture photometry calibrated against Pan-STARRS DR1 magnitudes (Chambers et al., 2016). The photometry includes host galaxy light, but we expect its contribution to be small. 

+---------------------------------------------+
| Time (UT)           | filter | mag   | err  |
+---------------------+--------+-------+------+
| 2019-12-14 11:14:14 | g      | 19.83 | 0.04 |
| 2019-12-14 11:17:48 | i      | 20.23 | 0.15 |
| 2019-12-14 11:24:48 | r      | 20.11 | 0.05 |
+---------------------+--------+-------+------+

Our LCOGT measurements are consistent with ZTF photometry of ZTF19acymaru/AT2019wnh (GCN #26424) within the uncertainties. The time lag of ~3hr between ZTF and LCOGT observations at >1 day from the merger is too short to exclude any rapid variability. However, we notice that a pre-detection from Pan-STARRS1 exists for this source on 2019-12-04 (TNS report). In light of this, we exclude that ZTF19acymaru/AT2019wnh is associated with S191213g.


We thank the TOM Community Development Program and the TOM Toolkit Workshop organizers for the generous LCOGT time allocation. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA, WIS, Israel; OKC, Sweden; JSI/UMd, USA; U Washington, USA; DESY, Germany; MOST, Taiwan; UW Milwaukee, USA; LANL USA; Tokyo Tech, Japan; IITB, India; IIA, India; LJMU, UK; TTU, USA; SDSU, USA and USyd, Australia.