Irradiation-Driven Formation of Supersoft X-ray Sources Following Classical Novae

TL;DR

This paper proposes a new formation channel for supersoft X-ray sources driven by irradiation effects after classical novae, explaining observed short-period SSSs and recurrent novae through detailed binary evolution simulations.

Contribution

The study introduces a novel irradiation-driven mechanism for sustained mass transfer in white dwarf binaries, supported by detailed MESA simulations, addressing a key theoretical paradox.

Findings

Irradiation from nova outbursts triggers stable mass transfer in low-mass companions.

This mechanism sustains hydrogen burning for over 10,000 years, matching observations.

It also explains the transition to recurrent nova outbursts when mass transfer drops below stable rates.

Abstract

Supersoft X-ray sources (SSSs) are characterized by persistent thermonuclear burning on the surfaces of white dwarfs (WDs).The standard model requires high mass transfer rates of $\sim 10^{-7}\, {\rm M_{\odot}}\,yr^{-1}$ from massive companions, presenting a theoretical impediment to the observed short-period SSSs, whose orbital periods imply low-mass donors theoretically incapable of sustaining such accretion.To resolve this paradox,we propose and demonstrate through detailed simulations that irradiative feedback following a classical nova (CN) eruption provides a natural formation channel.Through detailed binary evolution simulations with MESA, we reveal that sustained WD irradiation initially from the outburst and subsequently from accretion luminosity triggers significant and stable expansion of the low mass companion.This,in turn,drives mass-transfer rates into the stable hydrogen-burning regime and sustains it beyond $10^4$ years after the initiation of hydrogen burning.This mechanism robustly explains the observed population of short-period SSSs. Moreover,when irradiation-driven mass transfer rate drops below the stable accretion rate,it may lead to the rapid accumulation of sufficient material on shorter time scales to trigger a recurrent nova outburst instead of SSS, thereby also offering an explanation for the origin of short-period recurrent novae.