TITLE: GCN CIRCULAR NUMBER: 38434 SUBJECT: IceCube-241127A: No transient candidates from the Zwicky Transient Facility DATE: 24/12/03 18:53:03 GMT FROM: Robert David Stein at JSI <rdstein@umd.edu> Robert Stein (JSI), Sven Weimann (Ruhr University Bochum), Jannis Necker (DESY), Anna Franckowiak (Ruhr University Bochum) and Jesper Sollerman (Stockholm University) 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 IceCube-241127A (Zegarelli et. al, GCN 38349) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). As a result of delays due to bad weather, we started observations in the g- and r-band beginning at 2024-11-29 10:38 UTC, approximately 44.4 hours after event time. We covered 95.5% (1.0 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 find one candidates lying within the 90.0% localization of the skymap. +---------------------------------------------------------------------------------+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | +---------------------------------------------------------------------------------+ | ZTF19aasljeo | AT2022aelp | 163.5871140 | +05.9265829 | g | 19.23 | 0.14 | +---------------------------------------------------------------------------------+ ZTF19aasljeo is a nuclear source that was first detected on 2019-04-27, and has a long history of variability in ZTF. The source has a crossmatched detection as WISEA J105420.91+055535.5 at a distance of 0.25", and based on the WISE colours of the galaxy (W1-W2 = 1.07), ZTF19aasljeo is very likely an AGN. Over the past two months the source has been detected in difference imaging with a magnitude of g ~ 19.3. In historical detections over the past two years, the source was detected at a fainter level of g ~ 20. In reference science images from PS1 (Chambers et al. 2016), the source was detected at a much fainter level of g = 21.3, demonstrating that the source has brightened substantially in recent years. However, there are no indications of significant flaring on timescales of either weeks or months that coincide with the detection of IC241127A. We therefore find no strong evidence from our data to suggest that this AGN is associated with the neutrino. Observations of this field will continue as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). 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 the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/38434. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...