TITLE: GCN CIRCULAR NUMBER: 34810 SUBJECT: IceCube-231004A: One Candidate Counterpart from the Zwicky Transient Facility DATE: 23/10/10 17:57:45 GMT FROM: Simeon Reusch at DESY <simeon.reusch@desy.de> Simeon Reusch (DESY), Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Jannis Necker (DESY) and Anna Franckowiak (DESY/Ruhr University Bochum) report: On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IC231004A (Lincetto et al, GCN 34797) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2023-10-05 11:54 UTC, approximately 21.3 hours after event time. We covered 84.2% (3.1 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 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). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We are left with the following candidate counterpart: +-----------------------------------------------------------------+ | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | +-----------------------------------------------------------------+ | AT2023uqf | 143.4548956 | +25.1158103 | r | 20.51 | 0.11 | +-----------------------------------------------------------------+ AT2023uqf (ZTF23abidzvf) has a g-r color of 0.1 +/- 0.1 mag, no ZTF pre-detections and it is slowly rising. Spectroscopic observations of this source are planned, and monitoring of the neutrino localization will continue as part of our standard 10-day monitoring program. ZTF and GROWTH are worldwide collaborations comprising Caltech, USA; IPAC, USA; WIS, Israel; OKC, Sweden; JSI/UMd, USA; DESY, Germany; TANGO, Taiwan; UW Milwaukee, USA; LANL, USA; TCD, Ireland; IN2P3, France. 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). Alert filtering is performed with nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf). View this GCN Circular online at https://gcn.nasa.gov/circulars/34810. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...