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GCN Circular 26747

IceCube-200109A: Candidate Counterparts from the Zwicky Transient Facility
2020-01-14T15:44:12Z (4 years ago)
Simeon Reusch at DESY <>

Simeon Reusch and Robert Stein (DESY) report,��

On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of
Observatories Watching Transients Happen (GROWTH) collaborations:

We observed the localization region of the neutrino event
IceCube-200109A (Stein et. al, GCN 26696) 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 and
r-band beginning at 2020-01-11T08:03:45.800 UTC, approximately 32.4
hours after event time due to bad weather. We covered 22.4 sq deg,
corresponding to the entire localisation region. This estimate accounts
does not account 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) 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 high-significance
transient candidates by our pipeline, all lying within the 90.0%
localization of the neutrino.��


| ZTF Name �� �� | IAU Name | RA (deg) �� | DEC (deg) | Filter | Mag �� |
MagErr |


| ZTF19acmwlds | AT 2019yfm | 163.8379011| +11.0507782 | r�� �� �� | 20.74
| 0.13 |��

| ZTF20aaeuufe | AT 2019yii | 161.616044 | +10.8570761 | r�� �� �� | 20.80
| 0.18 |����

| ZTF20aaevfwa | AT 2019zxa | 162.7251345| +12.9120284 | r�� �� �� | 21.13
| 0.21 |��

| ZTF20aaevgvt | AT 2020uw�� | 162.25426 | +10.6885268 | r�� �� �� | 20.54 |
0.16 |��


AT 2019yfm was reported to the TNS by the Pan-STARRS1 survey (Chambers,
et al. 2019), who first detected it on 2019-11-02. This object was first
detected by ZTF on 2019-10-29, and has since faded by 1 mag. AT 2019yii
was also first reported by Pan-STARRS1 to the TNS, with a discovery on
2019-12-24. ZTF first detected it on 2019-12-29.ZTF20aaevfwa (AT
2019zxy) was first detected on 2019-12-29. It has a hostspectroscopic
redshift of z=0.13, which gives it an absolute magnitude of -17.91.
These three objects have lightcurves consistent with supernovae that are
now post-peak.

ZTF20aaevgvt (AT 2020uw) was first detected on 2020-01-07. There is no
apparent host galaxy. This candidate is consistent with being young SNe.��

The arrival of a neutrino from any of these four objects would be
consistent with a supernova CSM-interaction model for neutrino production.

We encourage spectroscopic and photometric observations to discern the
nature of the four unclassified objects listed above.

Additional observations of the localisation region of IceCube 200109A
will continue as part of the regular survey operations.

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; IIT-B, 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). Alert filtering and follow-up co-ordination
is being undertaken by the GROWTH marshal system (Kasliwal et al. 2019).

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