GCN Circular 34973
Subject
IceCube-231103A: No candidates from the Zwicky Transient Facility
Date
2023-11-09T18:56:46Z (a year ago)
From
Robert Stein at Caltech <rdstein@astro.caltech.edu>
Via
Web form
Robert Stein (Caltech), Sven Weimann (Ruhr University Bochum), Anna Franckowiak (DESY/Ruhr University Bochum), Jannis Necker (DESY), Simeon Reusch (DESY), Jesper Sollerman (OKC), Theophile du Laz (Caltech) 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-231103A (Blaufuss et. al, GCN 34933) 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 2023-11-03 09:24 UTC, approximately 0.1 hours after event time. We covered 84.1% (12.9 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). After removing low-level AGN variability, we are left with one following high-significance transient candidate by our pipeline, lying within the 90.0% localization of the skymap:
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| ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr |
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| ZTF23abnoapt | AT2023wue | 102.9192032 | +48.0780348 | g | 17.98 | 0.05 |
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ZTF23abnoapt was first detected on 2023-10-27, with a fast rise, slow decay and blue colour resembling a CV. We obtained a follow-up spectrum with the SEDm (Blagorodnova et al. 2018), which confirmed a blue continuum as expected for a CV, and a SNID best-fit to a galactic source. We therefore consider it likely that ZTF23abnoapt is unrelated to the neutrino.
We note that one additional variable source in the localisation, ZTF19aaenfez, appears to be undergoing an extended optical flare. The source is WISE-detected (WISEA J065203.55+473924.6), and is a probable AGN based on WISE colours (W1-W2=0.95). The source is approximately 50% brighter in flux than the median across the 5-year baseline of ZTF. The flare has been ongoing for over one year in ZTF data.
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 ).