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GCN Circular 33858

LIGO/Virgo/KAGRA S230521k: Additional candidates from Zwicky Transient Facility
2023-05-23T20:38:13Z (16 days ago)
Vishwajeet Swain at IIT Bombay <>
Vishwajeet Swain (IITB), Harsh Kumar (IITB), Viraj Karambelkar (CIT), Anirudh Salgundi (IITB), Akash Anumarlapudi (UWM), Robert Stein (CIT), Tomas Ahumada (CIT), Michael Coughlin (UMN), Mansi Kasliwal (CIT), Theophile du Laz (CIT), Eric Bellm (UW), Igor Andreoni (UMD) report on behalf of the ZTF collaboration: Zwicky Transient Facility (ZTF; Graham et al., 2019; Bellm et al., 2019) continued to serendipitously cover the localization region of LVC trigger S230521k. In our previous GCN #33848 (T. Ahumada et al), we announced two candidates from observations on the first night. Continued observations cover 20.5% of the probability of the localization region at least twice. We queried the ZTF alert stream using Kowalski (Duev et al. 2019) through Fritz (Coughlin et al. 2023) and emgwcave (Karambelkar et al. in prep), AMPEL (Nordin et al. 2019), and ZTFReST (Andreoni & Coughlin et al., 2021). We required at least 2 detections separated by at least 15 minutes to select against moving objects. Furthermore, we cross-match our candidates with the Minor Planet Center to flag known asteroids, reject stellar sources (Tachibana and Miller 2018), and apply machine learning algorithms (Mahabal et al. 2019). We require that no spatially coincident ZTF alerts were issued before the detection time of the LVC trigger. The following sources passed our criteria and were inside the 95% error region: |----------------------------------------------------------------------------------------------------- | ZTF id | TNS name | ra | dec | mjd | mag±err (ab) | filter | |----------------------------------------------------------------------------------------------------- ZTF23aalczjh | AT2023jfn | 202.39335 | 70.869591 | 60086.23392 | 20.25 ± 0.16 | g | ZTF23aalczjc | --------- | 187.26158 | 70.850479 | 60086.19871 | 20.18 ± 0.23 | r | ZTF23aakyfsk | AT2023jft | 180.89014 | 61.38805 | 60086.22718 | 20.40 ± 0.19 | g | ZTF23aalcvpw | AT2023jfp | 173.47154 | 29.19382 | 60086.19722 | 20.36 ± 0.26 | r | |----------------------------------------------------------------------------------------------------- We followed up ZTF23aalczjh, ZTF23aalczjc and ZTF23aakyfsk with 0.7m GROWTH-India Telescope and found that: ZTF23aalczjh and ZTF23aakyfsk are not showing any significant evolution. ZTF23aalczjc is blue (g-r = -0.22 ± 0.1 mag) and shows weak evidence of fading in r band (0.68 ± 0.55 mag/day), but g-band is consistent with no evolution. 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 database searches are done by AMPEL (Nordin et al. 2019) and Kowalski (Duev et al. 2019). The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available a
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