TITLE: GCN CIRCULAR NUMBER: 24443 SUBJECT: LIGO/Virgo S190510g: Public DECam Observations DATE: 19/05/10 06:15:13 GMT FROM: Igor Andreoni at Caltech Igor Andreoni (Caltech), Daniel A. Goldstein (Caltech), Michael Coughlin (Caltech), Mansi M. Kasliwal (Caltech), Peter E. Nugent (LBNL), Michael Medford (UC Berkeley), Shreya Anand (Caltech), Jennifer Barnes (Columbia), S. Bradley Cenko (NASA GSFC), Jeffrey Cooke (Swinburne), Jorge Martínez Palomera (UC Berkeley), Leo P. Singer (NASA GSFC), on behalf of the Global Relay of Observatories Watching Transients Happen (GROWTH) and ZTF collaborations: On 2019-05-10 06:00:00 UT we started the follow-up of the gravitational wave trigger S190510g (LIGO Scientific Collaboration and the Virgo Collaboration, GCN #24442) with the Victor M. Blanco 4m Telescope at Cerro Tololo Inter-American Observatory, equipped with the Dark Energy Camera (DECam). An observational tiling for the event was automatically and optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). The data from this program are immediately public and we invite anyone interested to search the images for optical counterparts. We are searching the images in real time for optical counterpart candidates using an image subtraction pipeline written for this program. The images are available under proposal ID 2019A-0205 from the NOAO archive (archive.noao.edu). For any questions on the data or the observations, please contact the PIs of this program, Danny Goldstein and Igor Andreoni (danny@caltech.edu, andreoni@caltech.edu). GROWTH and ZTF 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; TTU, USA; LANL USA; Tokyo Tech, Japan; IIT-B, India; IIA, India; LJMU, UK and USyd, Australia. ZTF acknowledges the generous support of the NSF under AST MSIP Grant No 1440341. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).