Expectation for the MeV Gamma-Ray Emission from Pair-Instability Supernovae
Ryo Sawada
arXiv:2503.21744v2 Announce Type: replace
Abstract: Pair-instability supernovae (PISNe) are predicted thermonuclear explosions of massive stars with helium core masses exceeding $sim 65M_odot$ and synthesize substantial amounts of radioactive $mathrm{^{56}Ni}$ ($M(mathrm{^{56}Ni})sim60M_odot$ in extreme cases). To investigate their observational signatures, we developed a multi-D Monte Carlo radiation transport code, assuming spherical symmetry in the background medium and the photon sources distribution, and performed simulations of gamma-ray and hard X-ray emissions from the decay chain $mathrm{^{56}Ni}tomathrm{^{56}Co}tomathrm{^{56}Fe}$. We find that key gamma-ray lines (847 and 1238 keV) from $mathrm{^{56}Co}$ decay in the $130M_odot$ helium core model can be detected up to 300-400 Mpc by next-generation MeV gamma-ray telescopes. In contrast, the signals from the $100M_odot$ model remain below the detection limits. Our results provide the template for gamma-ray follow-up observations of PISNe. Considering theoretical predictions and observational constraints, we estimate PISN event rates within 300 Mpc to be approximately 0.01-0.1 events per year, highlighting their rarity but also emphasizing their feasibility as targets for future gamma-ray observations over the decade.arXiv:2503.21744v2 Announce Type: replace
Abstract: Pair-instability supernovae (PISNe) are predicted thermonuclear explosions of massive stars with helium core masses exceeding $sim 65M_odot$ and synthesize substantial amounts of radioactive $mathrm{^{56}Ni}$ ($M(mathrm{^{56}Ni})sim60M_odot$ in extreme cases). To investigate their observational signatures, we developed a multi-D Monte Carlo radiation transport code, assuming spherical symmetry in the background medium and the photon sources distribution, and performed simulations of gamma-ray and hard X-ray emissions from the decay chain $mathrm{^{56}Ni}tomathrm{^{56}Co}tomathrm{^{56}Fe}$. We find that key gamma-ray lines (847 and 1238 keV) from $mathrm{^{56}Co}$ decay in the $130M_odot$ helium core model can be detected up to 300-400 Mpc by next-generation MeV gamma-ray telescopes. In contrast, the signals from the $100M_odot$ model remain below the detection limits. Our results provide the template for gamma-ray follow-up observations of PISNe. Considering theoretical predictions and observational constraints, we estimate PISN event rates within 300 Mpc to be approximately 0.01-0.1 events per year, highlighting their rarity but also emphasizing their feasibility as targets for future gamma-ray observations over the decade.