[vsnet-grb-info 23282] LIGO/Virgo S190425bv: No additional candidates from the Zwicky Transient Facility

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25381
SUBJECT: LIGO/Virgo S190425bv: No additional candidates from the Zwicky Transient Facility
DATE:    19/08/17 10:13:34 GMT
FROM:    Robert Stein at DESY  <robert.stein at desy.de>

Leo P. Singer (NASA GSFC), Mansi M. Kasliwal (Caltech), Michael W. Coughlin (Caltech), Anna Franckowiak (DESY), Robert Stein (DESY), Jannis Necker (DESY), Jesper Sollerman (OKC), Ariel Goobar (OKC), Shreya Anand (Caltech), Tomas Ahumada (UMD), Eric Bellm (UW), Igor Andreoni (Caltech), Dmitry Duev (Caltech), Kishalay De (Caltech), Matt Hankins (Caltech), Danny Goldstein (Caltech), Samaya Nissanke (UofA), Harsh Kumar (IITB), Varun Bhalerao (IITB), Joshua S. Bloom (UCB), David Kaplan (UWM), Daniel A. Perley (LJMU), S. Bradley Cenko (NASA) report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

We again observed the localization region of the gravitational wave trigger S190814bv (GCN 25324, GCN 25333) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019, GCN 25343). The tiling was optimally determined and triggered using the GROWTH Target of Opportunity marshal (Coughlin et al. 2019a, Kasliwal et al. 2019b). We started obtaining target-of-opportunity observations in the g-band, r-band and i-band filters beginning at UT 2019-08-16 10:48 UT. We covered 86% of the enclosed probability before 12-deg twilight and analyzed in real-time. Each exposure was 300s with a typical depth of ~20.0 mag due to the high airmass. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019) was used to vet candidates based on their light curves. After rejecting stellar sources (Tachibana and Miller 2018) and moving objects and applying machine learning algorithms (Mahabal et al. 2019), and after removing candidates with history of variability prior to the merger time, no new transient candidates were identified by our pipeline in the 90% localization.

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; IIT-B, India; IIA, India; LJMU, TTU, 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 at UW (Patterson et al. 2019). Alert filtering and follow-up co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).