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GCN Circular 24311

Subject
LIGO/Virgo S190425z: Additional Candidates from the Zwicky Transient Facility
Date
2019-04-28T00:01:16Z (5 years ago)
From
Shreya Anand at GROWTH Caltech <sanand@caltech.edu>
Shreya Anand (Caltech), Mansi M. Kasliwal (Caltech), Michael W. Coughlin (Caltech), Tomas Ahumada (UMD), Daniel A. Perley (LJMU), Varun Bhalerao (IITB), Danny Goldstein (Caltech), �Leo P. Singer (NASA GSFC), Igor Andreoni (Caltech), Dmitry Duev (Caltech), S. Bradley Cenko (NASA GSFC), Eric C. Bellm (UW), Kishalay De (Caltech), Anna Ho (Caltech), Harsh Kumar (IITB), Gaurav Waratkar (IITB), Chris Copperwheat (LJMU), Virginia Cunningham (UMD), Shaon Ghosh (UWM), Ariel Goobar (OKC), David Kaplan (UWM), Jesper Sollerman (OKC), Joshua S. Bloom (UCB), M. Bulla (OKC), Nobuyuki Kawai (Tokyo Tech), Yoichi Yatsu (Tokyo Tech), Katsuhiro Murata (Tokyo Tech), Hidekazu Hanayama (IAO), Takashi Horiuchi (IAO), G. C. Anupama (IIA), G. Helou (IPAC)

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations

We continued observations of the gravitational wave trigger S190425z (LVC et al. GCN 24168) with ZTF on UT 2019-04-26. We covered a total of 4950 sq deg in g-band and r-band with over 50% of the enclosed probability targeted based on the original sky map and 24% actual probability enclosed based on the new sky map. Each exposure on the second night was 90s, with a typical depth of 21 mag. See details in Kasliwal et al. GCN 24191 for additional details on data processing.

Objects with a spectroscopic host galaxy redshift higher than 0.1 were excluded and photometric redshifts, where available are noted below. Additional candidates with no detections prior to merger, inside the 90% localization area of the LALInference sky map are:

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ZTF Name | RA (deg) | DEC (deg) ��| Filter | Mag ��| Magerr �| Notes

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ZTF19aasckwd | 253.1643781 | �10.6022943 | r | 20.15 | 0.13 |

ZTF19aasfogv | 261.8430161 | -11.3338523 | g � | 20.53 | 0.18 | [hostless] [lowb]

ZTF19aasejil | 261.9458106 | ��1.6537207 | g | 20.53 | 0.14 | z~0.199 +/- 0.035 [nuc]

ZTF19aaryxjf | 254.5952784 | �-3.9847379 | g | 19.95 | 0.08 | z~0.083 +/- 0.015 [nuc]

ZTF19aascxux | 258.2933102 | �17.2938689 | g | 20.56 | 0.13 �

ZTF19aasdajo | 254.3550291 | �11.9961079 | g | 20.70 | 0.20 | z~0.292 +/- 0.067

ZTF19aasbamy | 231.2656676 | �24.9275799 | g | 20.66 | 0.15 | z~0.201 +/- 0.047

ZTF19aasckkq | 248.4131017 | �13.9101828 | g | 20.86 | 0.18 | z=0.0528 [specz]

ZTF19aarycuy | 244.0832042 | �21.7409392 | r | 20.07 | 0.15 | z~0.127 +/- 0.011 [nuc]

ZTF19aasbphu | 245.5831354 | �21.4081853 | r | 19.71 | 0.13 | z~0.0971 +/- 0.0292

�ZTF19aasbaui | 235.2496342 | �24.0816102 | g | 20.49 | 0.14 | z~0.216 +/- 0.052

�ZTF19aarxxwb | 288.6933231 | �-3.0075058 | g | 18.89 | 0.07 | [hostless] [lowb]

�ZTF19aashlts | 253.1875476 | -19.0941338 | r � | 19.95 | 0.11 | [lowb]

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Notes:

[specz] : Spectroscopic redshift.

[hostless] : No discernable host galaxy.

[nuc] : Close to the host nucleus

[lowb] : Galactic latitude less than 20 degrees

Our most promising event is ZTF19aasckkq as it is -16.3 absolute mag  and we encourage follow-up. We also encourage due diligence follow-up of ZTF19aasckwd and ZTF19aascxux. We caution these targets are somewhat fainter and our upper limits relatively less constraining on age. We also caution that we cannot rule out the supernova hypothesis.

Additional follow-up and analysis is ongoing.

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, UK; TTU 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 co-ordination is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).
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