On burning regimes and long duration X-ray bursts

TL;DR

This paper reviews various thermonuclear burning regimes on neutron stars, focusing on rare long-duration X-ray bursts and their potential observability with specific instruments, highlighting current theory-observation discrepancies.

Contribution

It analyzes different burning regimes, discusses inconsistencies between models and observations, and evaluates the detectability of rare superbursts with INTEGRAL-ISGRI and Swift-BAT.

Findings

Only the brightest superbursts are detectable with current instruments.

Rare helium- and carbon-fueled bursts provide insights into neutron star crust properties.

Current models face challenges explaining all observed burst phenomena.

Abstract

Hydrogen and helium accreted onto a neutron star undergo thermonuclear burning. Explosive burning is observed as a type I X-ray burst. We describe the different burning regimes and focus on some of the current inconsistencies between theory and observations. Of special interest are the rare kinds of X-ray bursts such as carbon-fueled superbursts and helium-fueled intermediately long X-ray bursts. These bursts are thought to originate deeper in the neutron star envelope, such that they are probes of the thermal properties of the crust. We investigate the possibility of observing superbursts with the wide-field instruments INTEGRAL-ISGRI and Swift-BAT. We find that only the brightest bursts are detectable.