{
  "bibcode": "2022GCN.31989....1S",
  "body": "Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Simeon Reusch (DESY), Jannis Necker (DESY) and Anna Franckowiak (DESY/Ruhr University Bochum),\n\nOn behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: \n\nAs part of the ZTF neutrino follow up program (Stein et al. 2022),\nwe observed the localization region of the neutrino event IceCube-220501A (Santander et. al, GCN 31986) 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-band beginning at 2022-05-02 09:39 UTC, approximately 10.8 hours after event time. We covered 87% (2.5 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. \n \nThe 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).\n\nNo candidate counterparts were detected.\n\nZTF 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.\n\nGROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949.\nAlert distribution service provided by DIRAC@UW (Patterson et al. 2019).\nAlert database searches are done by AMPEL (Nordin et al. 2019).\nAlert filtering is performed with the AMPEL Follow-up Pipeline (Stein et al. 2021).",
  "circularId": 31989,
  "createdOn": 1651513451000,
  "email": "jannis.necker@desy.de",
  "subject": "IceCube-220501A: No Candidate Counterparts from the Zwicky Transient Facility",
  "submitter": "Jannis Necker at DESY  <jannis.necker@desy.de>",
  "eventId": "IceCube-220501A"
}