Detection horizon for the neutrino burst from the stellar helium flash

TL;DR

This paper analyzes the potential for detecting neutrino bursts from the helium flash in low-mass stars, emphasizing the challenges and prospects with current and future neutrino observatories.

Contribution

It introduces the detection horizon for neutrino bursts from the helium flash and assesses the capabilities of next-generation neutrino detectors.

Findings

Detection horizon extends to nearly 3 parsecs with future facilities.

Helium flashes occur multiple times per year in our Galaxy.

Current observatories face significant background challenges.

Abstract

Low-mass stars ($M\lesssim 2\,M_\odot$) ignite helium under degenerate conditions, eventually causing a nuclear run-away -- the helium flash. The alpha-capture process on $^{14}$N produces a large amount of $^{18}$F, whose subsequent decay spawns an intense $\nu_e$ burst (with average energy of $0.38$ MeV) lasting about a day. We show that, in addition, a strong $1.7$ MeV neutrino line is generated by electron capture on $^{18}$F. Detection is hindered by large backgrounds in state-of-the-art neutrino observatories, such as JUNO. In next-generation facilities, such as the Jinping neutrino experiment, the horizon for a detection with a local significance of $3 \sigma$ would be extended to almost $3$ pc. Although helium flashes occur a few times per year in our Galaxy, there are no stellar candidates approaching the tip of the red giant branch within $10$ pc. Hence, to date, asteroseismology remains the most promising tool for probing the most energetic thermonuclear event in the life of a low-mass star.