Multiwavelength modelling the SED of supersoft X-ray sources III. RS Ophiuchi: The supersoft X-ray phase and beyond

TL;DR

This study models the spectral energy distribution of RS Ophiuchi during its supersoft X-ray phase and quiescence, revealing details about the accretion process, WD mass growth, and implications for future outbursts.

Contribution

It provides a detailed multiwavelength model of RS Oph's SED during different phases, estimating accreted and burned mass, and constraining the WD's growth rate and outburst timing.

Findings

The SED during the SSS phase shows a strong stellar and nebular component.

The WD mass growth rate is approximately 4 x 10^-7 M_sun/yr.

The next outburst could occur before or after 2027 depending on accretion mechanisms.

Abstract

I modelled the 14 \AA - 37 $\mu$m SED of the recurrent symbiotic nova RS Oph during its supersoft source (SSS) phase and the following quiescent phase. During the SSS phase, the model SEDs revealed the presence of a strong stellar and nebular component of radiation in the spectrum. The former was emitted by the burning WD at highly super-Eddington rate, while the latter represented a fraction of its radiation reprocessed by the thermal nebula. During the transition phase, both the components were decreasing and during quiescence the SED satisfied radiation produced by a large, optically thick disk (R(disk) > 10 R(Sun)). The mass of the emitting material was (1.6 +/- 0.5) x 1E-4(d/1.6 kpc)**(5/2) M(Sun). The helium ash, deposited on the WD surface during the whole burning period, was around of 8 x 1E-6(d/1.6kpc)**2 M(Sun), which yields an average growing rate of the WD mass, dM(WD)/dt ~ 4 x 1E-7(d/1.6 kpc)**2 M(Sun)/yr. The mass accreted by the WD between outbursts, m(acc) ~ 1.26 x 1E-5 M(Sun), constrains the average accretion rate, dM(acc)/dt ~ 6.3 x 1E-7 M(Sun)/yr. If the wind from the giant is not sufficient to feed the WD at the required rate, the accretion can be realized from the disk-like reservoir of material around the WD. In this case the time between outbursts will extend, with the next explosion beyond 2027. In the opposite case, the wind from the giant has to be focused to the orbital plane to sustain the high accretion rate at a few times 1E-7 M(Sun)/yr. Then the next explosion can occur even prior to 2027.