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Cosmic-rays and high-energy astrophysics
(see arXiv:2310.16823 and arXiv:2405.17409)
Model the astrophysical environments, especially around supernovae
Calculate the effects of cosmic-ray acceleration
Resulting neutrinos
Composition
Observed flux
Section TBD
Quasithermal neutrinos
Neutrons in the supernova wind decouple from protons
Relative Lorentz factor with SN ejecta can be large enough to produce pions
Pions decay, producing neutrinos
Number of events depends on neutron star properties: magnetic field and spin
Signatures of nucleosynthesis
(see arXiv:2201.03576, arXiv:2303.00765, and arXiv:2502.07888)
Model the thermodynamic conditions required for nucleosynthesis in outflows of black hole-neutron star (BHNS) mergers, binary neutron star (BNS) mergers, and supernovae
Quantify abundance of r-process elements synthesized
Prospects for detecting kilonovae and gamma-rays from radioactive decay
What is the r-process?
Rapid neutron-capture process
~100 neutrons captured onto seed nuclei every second
Neutron-capture: abundances increase to the right in this figure
Three peaks (purple lines)
Unstable nuclei decay back to stable nuclei (black line)
Does this occur in supernovae? Compact object mergers? Other sites?
Abundance patterns from supernova outflows
The nuclei synthesized (here, average mass number) depends on the central engine properties like magnetic field and spin
Here, we assume the supernova wind is driven by a protomagnetar
Intermediate-mass nuclei can be synthesized, but very heavy elements from r-process unlikely
Abundance patterns from merger outflows
Heavier nuclei are synthesized in BHNS/BNS merger outflows
Very massive nuclei formed in the dynamical ejecta of mergers
r-process
Massive, unstable nuclei decay and give rise to a kilonova (KN)
Gamma-rays from radioactive decays
Radioactive nuclei produce gamma-rays when they decay
If they are entrained in relativistic jets, their half-life and energies can be boosted
Detectable given favorable distance, viewing angle, and instruments
* Figure courtesy of Sean Heston
The diffuse supernova neutrino background (DSNB)
(see arXiv:2206.05299, arXiv:2306.16076, and arXiv:2310.15254)
The DSNB is the isotropic background of ~10 MeV neutrinos from all past core collapse supernovae
Need to model the rate of core collapse, neutrino emission spectra from supernovae, and detector response
Star formation and core collapse rates
Massive stars undergo core collapse on very short timescales compared to cosmological timescales
So star formation rate ~ core collapse rate
Star formation rate uncertainty is low
Many tracers of star formation measured
Measuring core collapse rate directly is difficult to high redshift and large uncertainties
Data available at https://github.com/nekanger/Ekanger2023
Quantify the theoretical error
DSNB event rate and flux depends on a number of ingredients whose error we can quantify:
Star formation rate measurements (SFRD)
Neutrino emission in the late-phase (LP)
Fraction of failed supernovae that lead to black holes (BH)
Cosmology (H0) and initial mass function (IMF) assumptions
Detection prospects
DSNB detectable in Super-Kamiokande with gadolinium (SK-Gd) and Jiangmen Underground Neutrino Observatory (JUNO)
Significantly detected in the 2030s
HK and DUNE will complement these detectors
PyDSNB!
Publicly available code to calculate the flux of DSNB
Green, blue, and orange spectra here created with the code and compared to recent Super-Kamiokande flux upper limits
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