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GCN Circular 34751

Subject
LIGO/Virgo/KAGRA S230904n: Classification of the candidate AT2023rkw with DBSP
Date
2023-09-20T21:02:04Z (10 months ago)
From
Shreya Anand at GROWTH Caltech <sanand@caltech.edu>
Via
email
Shreya Anand (Caltech), Jannis Necker (DESY), Nicholas Earley (Caltech), Yu-Jing Qin (Caltech), Simeon Reusch (DESY), Joel Johansson (SU), Tomas Ahumada (Caltech), and Christoffer Fremling (Caltech) report on behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations:

We observed the candidate AT2023rkw [1,2] with the Double Beam Spectrograph (DBSP) mounted on the Palomar 200-in telescope on 2023-09-16 (UTC), using a setup with a red grating of 316/7500, a blue grating of 600/400, a D55 dichroic, and a slitmask of 1.5". The data were reduced using a custom DBSP pipeline relying on Pypeit [3,4]. The spectrum exhibits narrow host galaxy lines at a redshift of z=0.113. We observe weak Si II lines characteristic of a SN Ia (91T-like), which is re-affirmed by the astrodash best match template. Therefore, we conclude that AT2023rkw is unrelated to the event S230904n.

We thank the Palomar observatory staff for making these observations possible.

[1] ZTF and GROWTH Collaborations, GCN 34688
[2] ZTF and GROWTH Collaborations, GCN 34717
[3] Prochaska et al. 2019
[4] Roberson et al. 2021

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). GROWTH India telescope is located at the Indian Astronomical Observatory (Hanle), operated by the Indian Institute of Astrophysics (IIA). GROWTH-India project is supported by SERB and administered by IUSSTF, under grant number IUSSTF/PIRE Program/GROWTH/2015-16 and IUCAA.

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