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GCN Circular 35048

GRB 231115A: pre-burst ZTF upper limits for GRB optical counterpart candidate
2023-11-15T22:21:51Z (3 months ago)
Tomas Ahumada Mena at Caltech <>
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Tomas Ahumada (CIT), Jacob Wise (LJMU), Michael Coughlin (UMN), on behalf of the ZTF and GROWTH collaboration: 

We serendipitously observed the localization region of GRB 231115A (GCN 35035) as part of routine Zwicky Transient Facility (ZTF; Graham et al., 2019; Bellm et al., 2019) survey operations. We most recently obtained images in the g-, and r-bands beginning ~1.2 days before the trigger time.  We report recent upper limits for the GRB optical counterpart candidate AT 2023xvj/GIT231115aa (GCN 35041) in the table below: 

Filter | mjd | mag lim (AB mag)
r  | 60262.4944329 | 20.47
g | 60262.4463542 | 20.37

Additionally, we ran forced photometry on ZTF images (Masci et al. 2019) at the location of the transient, and found no previous activity at the 4 sigma level since the beginning of the ZTF survey (March 2018).

We note the latest ATLAS (Tonry et al. 2018, Smith et al. 2020) observations of the field were 7 days prior to the burst, reaching a limit of 19.2 mag in the r-band.

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. Fritz and SkyPortal acknowledge the generous support of The Gordon and Betty Moore Foundation, through the Data-Driven Investigator Program.

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