TITLE: GCN CIRCULAR NUMBER: 27051 SUBJECT: LIGO/Virgo S200213t: Candidates from the Zwicky Transient Facility DATE: 20/02/13 07:32:59 GMT FROM: Mansi M. Kasliwal at Caltech/Carnegie Mansi M. Kasliwal (Caltech), Daniel Perley (LJMU), Harsh Kumar (IITB), Igor Andreoni (Caltech), Kishalay De (Caltech), Viraj Karambelkar (Caltech), Varun Bhalerao (IITB), Erik Kool (OKC), Jesper Sollerman (OKC), Ana Carracedo (OKC), Michael Coughlin (U Minn), Eric Bellm (UW), Leo Singer (NASA GSFC), Shreya Anand (Caltech), Tomas Ahmuda (UMd) on behalf of the ZTF and GROWTH collaborations We observed the localization region of the gravitational wave trigger S200213t (LVC, GCN #27042) with the Palomar 48-inch telescope equipped with the 47 square degree Zwicky Transient Facility camera (ZTF, Bellm et al. 2019, Graham et al. 2019). 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 and r-band beginning at 2020-02-13 04:36 UT, targeting ~77% of the enclosed probability based on the bayestar skymap (LVC, GCN #27042). Each exposure was 120s with a median depth of ~20.7 mag. 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). Alert filtering and follow-up coordination was undertaken by the GROWTH Marshal system (Kasliwal et al. 2019). The ZTF alert stream was also queried using the Kowalski infrastructure (Duev et al., 2019). We required at least 2 detections separated by at least 30 minutes to select against moving objects. Furthermore, we cross-matched our candidates with the Minor Planet Center to flag known asteroids. Candidates that passed our selection are: +--------------+----------+-------------+--------------+--------+------+----------+-------+ | Name | IAU Name | RA | Dec | filter | mag | MJD | Notes | +--------------+----------+-------------+--------------+--------+------+----------+-------+ | ZTF20aamvqxl | AT2020ciy | 01:56:57.10 | +53:40:07.97 | r | 20.1 | 58892.22 | Offset from Host Galaxy | | ZTF20aamvnth | AT2020cjb | 01:13:21.05 | +49:38:43.94 | g | 20.4 | 58892.20 | Offset from Host Galaxy | | ZTF20aamvoxx | AT2020cjg | 02:37:35.78 | +26:55:14.22 | g | 20.0 | 58892.21 | SDSS phot-z 0.110 +/- 0.008 | | ZTF20aamvtip | AT2020cje | 02:32:19.81 | +27:48:36.34 | r | 20.6 | 58892.24 | SDSS phot-z 0.22 +/- 0.06 | | ZTF20aamvnat | AT2020ciz | 01:48:57.49 | +56:21:16.49 | g | 19.0 | 58892.21 | Faint Red Counterpart in PS1 | | ZTF20aamvmzj | AT2020cja | 01:48:45.41 | +51:25:49.73 | g | 20.6 | 58892.20 | Hostless | | ZTF20aamvoeh | AT2020cjc | 02:14:00.48 | +38:56:10.74 | g | 20.6 | 58892.21 | Nuclear/Stellar? | | ZTF20aamvodd | AT2020cjf | 02:29:55.77 | +50:19:09.94 | g | 19.7 | 58892.20 | Faint Red Counterpart in PS1 | +--------------+----------+-------------+--------------+--------+------+----------+-------+ We encourage follow-up to classify the candidates. We caution that these candidates are low Galactic latitude and the magnitudes reported are not extinction corrected. 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. 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 coordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019). Alert database searches are done with using the Kowalski infrastructure (Duev et al., 2019) and with AMPEL (Nordin et al. 2019).