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1. Searching for high-energy neutrinos from the most luminous supernovae with the IceCube Neutrino Observatory

   https://doi.org/10.1051/epjconf/202328005005  

   Lincetto, Massimiliano (January 2023, EPJ Web of Conferences)

   Capone, A.; De Vincenzi, M.; Morselli, A. (Ed.)

   The sources of the astrophysical neutrino flux discovered by IceCube remain for the most part unresolved. Extragalactic core-collapse supernovae (CCSNe) have been suggested as potentially able to produce high-energy neutrinos. In recent years, the Zwicky Transient Facility has discovered a population of exceptionally luminous supernovae, whose powering mechanisms have not yet been fully established. A fraction of these objects fall in the broader category of type IIn CCSNe, showing signs of interaction with a dense circumstellar medium. Theoretical models connect the supernova photometric properties to the dynamics of a shock-powered emission, predicting particle acceleration. In this contribution, we outline the plan for a search of high-energy neutrinos targeting the population of superluminous and type IIn supernovae with the IceCube Neutrino Observatory. 

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2. Low-energy supernovae bounds on sterile neutrinos

   https://doi.org/10.1088/1475-7516/2025/03/052  

   Chauhan, Garv; Horiuchi, Shunsaku; Huber, Patrick; Shoemaker, Ian M (March 2025, Journal of Cosmology and Astroparticle Physics)

   Abstract Sterile neutrinos can be produced through mixing with active neutrinos in the hot, dense core of a core-collapse supernova (SN). The standard bounds on the active-sterile mixing (sin²θ) from SN arise from SN1987A energy-loss, requiringE_loss< 10⁵²erg. In this work, we discuss a novel bound on sterile neutrino parameter space arising from the energy deposition through its decays inside the SN envelope. Using the observed underluminous SN IIP population, this energy deposition is constrained to be below ∼ 10⁵⁰erg. Focusing on sterile neutrino mixing only with tau neutrino, for heavy sterile massesm_sin the range 100 – 500 MeV, we find stringent constraints on sin²θ_τreaching two orders of magnitude lower than those from the SN1987A energy loss argument, thereby probing the mixing angles required for Type-I seesaw mechanism. Similar bounds will also be applicable to sterile mixing only with muons (sin²θ_μ). 

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3. Probing the sterile neutrino dipole portal with SN1987A and low-energy supernovae

   https://doi.org/10.1103/PhysRevD.110.015007  

   Chauhan, Garv; Horiuchi, Shunsaku; Huber, Patrick; Shoemaker, Ian M (July 2024, Physical Review D)

   Beyond the Standard Model electromagnetic properties of neutrinos may lead to copious production of sterile neutrinos in the hot and dense core of a core-collapse supernova. In this work, we focus on the active-sterile transition magnetic moment portal for heavy sterile neutrinos. Firstly, we revisit the SN1987A cooling bounds for dipole portal using the integrated luminosity method, which yields more reliable results (especially in the trapping regime) compared to the previously explored via emissivity loss, also known as the Raffelt criterion. Secondly, we obtain strong bounds on the dipole coupling strength reaching as low as 10^{-11} /GeV from energy deposition, i.e., constrained from the observation of explosion energies of underluminous Type IIP supernovae. In addition, we find that sterile neutrino production from Primakoff upscattering off of a proton dominates over scattering off of an electron for low sterile neutrino masses. 

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4. Diffuse boosted cosmic neutrino background

   https://doi.org/10.1103/PhysRevD.111.063016  

   Herrera, Gonzalo; Horiuchi, Shunsaku; Qi, Xiaolin (March 2025, Physical Review D)

   Energetic cosmic rays scatter off the cosmic neutrino background throughout the history of the Universe, yielding a diffuse flux of cosmic relic neutrinos boosted to high energies. We calculate this flux under different assumptions of the cosmic-ray flux spectral slope and redshift evolution. The nonobservation of the diffuse flux of boosted relic neutrinos with current high-energy neutrino experiments already excludes an average cosmic neutrino background overdensity larger than $\sim {10}^4$over cosmological distances. We discuss the future detectability of the diffuse flux of boosted relic neutrinos in light of neutrino overdensity estimates and cosmogenic neutrino backgrounds. 

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5. Supernova gamma-ray constraints from heavy sterile neutrino decays

   https://doi.org/10.1088/1475-7516/2025/07/012  

   Chauhan, Garv; Andrew_Gustafson, R; Shoemaker, Ian M (July 2025, Journal of Cosmology and Astroparticle Physics)

   Heavy sterile neutrinos can be produced in core-collapse supernovae (CCSNe), which are superb particle generators because of their high densities and temperatures. If the sterile neutrinos are long-lived, these may be produced inside the supernova core and escape the stellar envelope, later decaying into SM particles like photons and neutrinos. In this work, we first improve the original analytical calculation of the γ-ray fluxes from decays. We then revisit the bounds on the sterile neutrino parameter space from the non-observation of γ -rays from SN1987A by the Solar Maximum Mission (SMM) and constraints from the diffuse γ -ray background arising from sterile neutrino decays. We find that the constraints arising from both the SMM data and the diffuse γ -ray background are weaker than those that have previously appeared in the recent literature. Finally, we study the sensitivity of several present and near-future γ -ray telescopes such as e-ASTROGAM and Fermi-LAT, assuming a nearby future galactic CCSN. We show that future observations can probe mixing angles as low as |U_τ/μ4|²∼ 5 × 10^-17. 

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