Effect of Collective Neutrino Oscillations on the Neutrino Mechanism of Core-Collapse Supernovae

TL;DR

This study investigates whether collective neutrino oscillations significantly influence the neutrino-driven explosion mechanism in core-collapse supernovae, concluding that their impact is limited due to matter suppression effects.

Contribution

The paper provides a quantitative analysis of how collective neutrino oscillations affect the critical neutrino luminosity needed for supernova explosions, incorporating matter effects and parameter dependencies.

Findings

CnuO can reduce the critical luminosity by up to 1.5 times under ideal conditions.

Matter suppression diminishes the impact of CnuO on the explosion mechanism.

Realistic parameters suggest CnuO are unlikely to significantly influence supernova explosions.

Abstract

In the seconds after collapse of a massive star, the newborn proto-neutron star (PNS) radiates neutrinos of all flavors. The absorption of electron-type neutrinos below the radius of the stalled shockwave may drive explosions (the "neutrino mechanism"). Because the heating rate is proportional to the square of neutrino energy, flavor conversion of mu and tau neutrinos to electron-type neutrinos via collective neutrino oscillations (CnuO) may in principle increase the heating rate and drive explosions. In order to assess the potential importance of CnuO for the shock revival, we solve the steady-state boundary value problem of spherically-symmetric accretion between the PNS surface (r_nu) and the shock (r_S), including a scheme for flavor conversion via CnuO. For a given r_nu, PNS mass (M), accretion rate (Mdot), and assumed values of the neutrino energies from the PNS, we calculate the critical neutrino luminosity above which accretion is impossible and explosion results. We show that CnuO can decrease the critical luminosity by a factor of at most ~1.5, but only if the flavor conversion is fully completed inside r_S and if there is no matter suppression. The magnitude of the effect depends on the model parameters (M, Mdot, and r_nu) through the shock radius and the physical scale for flavor conversion. We quantify these dependencies and find that CnuO could lower the critical luminosity only for small M and Mdot, and large r_nu. However, for these parameter values CnuO are suppressed due to matter effects. By quantifying the importance of CnuO and matter suppression at the critical neutrino luminosity for explosion, we show in agreement with previous studies that CnuO are unlikely to affect the neutrino mechanism of core-collapse supernovae significantly.