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HUNTING FOR NEUTRINOS FROM HYBRID STARS AND OTHER NEW SOURCES Pablo Martínez-Miravé Niels Bohr Institute, Universtiy of Copenhagen XXI Workshop on Neutrino Telescopes 2nd October 2025
2 Not to scale, inspired by Vitagliano, Tamborra & Raffelt Rev. Mod. Phys. 92 (2020)
TeV – PeV (high-energy) NEUTRINOS keV – MeV (low-energy) NEUTRINOS 3 Not to scale, inspired by Vitagliano, Tamborra & Raffelt Rev. Mod. Phys. 92 (2020)
Neutrino telescopes could observe astrophysical neutrino sources so far overlooked, like hybrid stars (also known as Thorne-Zytkow Objects) and the cumulative neutrino flux expected at Earth from all stars in the Milky Way (the Galactic Stellar Neutrino Flux). 4
Ż THORNE-ŻYTKOW OBJECTS 5 PMM, I.Tamborra, A.Vigna-Gomez, ApJL [2501.03330]
Disclaimer: conceptual artistic impression Thorne, K. S., & Zytkow, A. N. 1975, Astrophys. J. Lett., 199, L19 Thorne, K. S., & Zytkow, A. N. 1977, Astrophys. J., 212, 832 6
CANDIDATES have been mainly identified through peculiar spectroscopic lines POTENTIAL PROGENITORS include •high-mass X-ray binaries in which the neutron star accretes matter from the stellar companion and unstable mass transfer is expected •stellar clusters where red supergiants are abundant 7 PMM, I.Tamborra, A.Vigna-Gomez, ApJL [2501.03330]
Neutrino emission from THORNE-ŻYTKOW OBJECTS 8
TŻO with an ACCRETION DISK For accretion rates 104 - 106 M⊙ yr−1, we assume that disk forms. Steady accretion onto a neutron star (1.4 M⊙ and radius of 10 km). In the surroundings of the neutron star, T ∼ 4×1010 – 8×1010 K , ρ ∼ 109 – 1011 g cm−3 . We follow Di Matteo et al. (2002)002, Astrophys.J., 579, 706; Zhang & Dai (2008) Astrophys. J., 683, 329. 9
Ż MILKY-WAY STARS PMM, I.Tamborra, (To appear soon) 16
Ż MILKY-WAY STARS PMM, I.Tamborra, (To appear soon) Stars with masses M > 0.9M⊙in the thin disk of the Milky Way, mainly towards the Galactic Center, are responsible for a flux of neutrinos and antineutrinos of all flavours with energies between ~1keV and ~20MeV. 17
SPATIAL DISTRIBUTION We model the stellar population of the Milky Way based on the baryon density inferred from Gaia DR2. We consider three components: the bulge, the thin disk, and the thick disk. 18 M. Cautun et al. MNRAS 494, 4291 494, 4291 (2020)
AGE DISTRIBUTION We assume a model of stellar formation based on two infalls. 19 V. Grisoni et al. MNAS 472, 3637 (2017)
20 MASS DISTRIBUTION We assume an isotropic Initial Mass Function P. Kroupa, MNRAS. 322, 231 (2001)
We model stellar evolution with the stellar evolutionary code MESA. 21 We compute the spectral flux at Earth from thermal and thermonuclear processes. Mass distribution Age distribution Spatial distribution
22 Stars with masses M > 0.9 M⊙ dominate the expected flux (but it would still be smaller than the flux from solar neutrinos)
23 Stars with masses M > 0.9 M⊙ dominate the expected flux (but it would still be smaller than the flux from solar neutrinos)
Ż MILKY-WAY STARS PMM, I.Tamborra, (To appear soon) 24 Stars with masses M > 0.9M⊙in the thin disk of the Milky Way, mainly towards the Galactic Center, are responsible for a flux of neutrinos and antineutrinos of all flavours with energies between ~1keV and ~20MeV.
Neutrino telescopes could observe astrophysical neutrino sources so far overlooked, like hybrid stars (also known as Thorne-Zytkow Objects) and the cumulative neutrino flux expected at Earth from all stars in the Milky Way (the Galactic Stellar Neutrino Flux). 25
TZOs contribute to a diffuse background of astrophysical thermal and themonuclear neutrinos (generalised DSNB). Current limits from the DSNB already exclude extreme scenarios where all TZOs reach very large accretion rates.* *this statement would depend on the cosmic rate of TZOs 32
33 RELEVANT THERMONUCLEAR REACTIONS
34 RELEVANT THERMAL REACTIONS
35 Main contribution comes from stars in the thin disk between 6kpc and 10kpc (in the direction of the Galactic Center
