J/A+A/708/A223 SN2025cbj LAST and ZTF photometric data (Garrappa+, 2026)
The Type IIn SN 2025cbj coincidence with the high-energy neutrino
IceCube-250421A.
Garrappa S., Zimmerman E.A., Wasserman T., Ofek E.O., Gal-Yam A., Konno R.,
Chen P., Yaron O., Ben-Ami S., Copperwheat C.M., Fainer S., Horowicz A.,
Humpe A., Mazzali P.A., Polishook D., Segre E., Spitzer S.A.
<Astron. Astrophys. 708, A223 (2026)>
=2026A&A...708A.223G 2026A&A...708A.223G (SIMBAD/NED BibCode)
ADC_Keywords: Supernovae ; Photometry ; Optical
Keywords: neutrinos - methods: observational -
techniques: imaging spectroscopy - techniques: photometric -
supernovae: general - supernovae: individual: SN2025cbj
Abstract:
The origins of astrophysical high-energy neutrino flux remain
uncertain. Core-collapse supernovae with strong CSM interaction (Type
IIn a.k.a. SNe IIn) are compelling candidates for efficient hadronic
acceleration and neutrino production.
We investigate the possible association between the Type IIn supernova
SN2025cbj and the IceCube high-energy neutrino IceCube-250421A, and
assess whether the observed properties of the SN permit an appreciable
neutrino yield.
We combined rapid optical follow-up with LAST and archival ZTF
photometry with spectroscopy from LT/SPRAT and MMT/BINOSPEC to
characterize the SN's evolution and CSM interaction. We estimated the
explosion and peak times from early light-curve fitting, and
quantified the chance-coincidence probability with resampling
simulations that scramble neutrino right ascensions while preserving
declinations and error contours. Using a simple post-shock-breakout
interaction model in a dense wind, we estimated the expected
muon-neutrino yield for IceCube's real-time Bronze stream.
Spectra of SN2025cbj obtained after the neutrino epoch show persistent
narrow Balmer lines superposed on broad Lorentzian electron-scattering
wings, consistent with sustained dense-CSM interaction. For the
multi-messenger association, resampling simulations against the TNS
catalog give a chance-coincidence probability for observing k≥1
events of p≃0.24 (and p≃0.078 against the ZTF-BTS catalog). These
values are sensitive to the size of the SNe and neutrino samples. A
post-breakout interaction scenario predicts an expected
Nνµ∼10-3 events in the IceCube Bronze alert stream over 76
days per this one candidate. We discuss the implications of these
numbers and possible biases that may affect these results.
Description:
This work reports on the spatial and temporal coincidence between the
Type IIn supernova SN2025cbj and the IceCube high-energy track alert
IceCube-250421A, discovered in rapid optical follow-up of the neutrino
localization. We present optical photometry from LAST and ZTF and
spectroscopy from LT/SPRAT and MMT/BINOSPEC to characterize the
supernova's circumstellar interaction and to estimate its explosion
and peak times. Using resampling simulations, we find that the
SN-neutrino association is consistent with chance coincidence
(p≃0.24 against the TNS SN IIn sample; p≃0.078 against ZTF-BTS), and
a simple post-shock-breakout interaction model predicts a low
expected muon-neutrino yield (Nνµ∼10-3) for IceCube's
real-time Bronze stream for this event. The CDS electronic material
includes the full LAST and ZTF photometric tables used to build the
light curve (Tables 1-2), while the optical spectra are available via
WISeREP.
LAST and ZTF photometry of the Type-IIn SN2025cbj. The LAST photometry
is from the official pipeline in Ofek et al. (2023PASP..135f5001O 2023PASP..135f5001O),
while the ZTF photometry is from ALeRCE ZTF Explorer
(https://alerce.online/object/ZTF25aagbrpb).
Objects:
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RA (2000) DE Designation(s)
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15 59 40.06 +27 06 40.8 SN2025cbj = ZTF25aagbrpb
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 58 13 Nightly average of LAST photometric
observations of SN2025cbj
table2.dat 46 87 ZTF photometric observations of SN2025cbj
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d MJD Modified Julian Date
20- 37 F18.15 mag mag Magnitude (AB)
39- 58 F20.18 mag e_mag Magnitude error
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 18 F18.12 d MJD Modified Julian Date
20- 28 F9.6 mag mag Magnitude in filter
30- 40 F11.9 mag e_mag Magnitude in filter error
42- 46 A5 --- Filter (ZTF-g ZTF-r) ZTF filter
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Acknowledgements:
Simone Garrappa, simone.garrappa(at)gmail.com
(End) Simone Garrappa [WIS], Patricia Vannier [CDS] 19-Feb-2026