Optical light curves of RS Oph (2006) and hydrogen burning turnoff

TL;DR

This study presents multi-band photometry of RS Oph's 2006 outburst, modeling its light curves to identify the hydrogen burning turnoff at day 80 and suggesting the white dwarf's potential as a Type Ia supernova progenitor.

Contribution

The paper introduces detailed theoretical modeling of RS Oph's light curves, linking the hydrogen burning turnoff to observable features and emphasizing the importance of y-filter observations.

Findings

Mid-plateau phase observed in y-band photometry.

Hydrogen shell-burning ends around day 80.

White dwarf mass estimated at 1.35 solar masses.

Abstract

We report a coordinated multi-band photometry of the RS Oph 2006 outburst and highlight the emission line free y-band photometry that shows a mid-plateau phase at y ~ 10.2 mag from day 40 to day 75 after the discovery followed by a sharp drop of the final decline. Such mid-plateau phases are observed in other two recurrent novae, U Sco and CI Aql, and are interpreted as a bright disk irradiated by the white dwarf. We have calculated theoretical light curves based on the optically thick wind theory and have reproduced the early decline, mid-plateau phase, and final decline. The final decline is identified with the end of steady hydrogen shell-burning, which turned out at about day 80. This turnoff date is consistent with the end of a supersoft X-ray phase observed with Swift. Our model suggests a white dwarf mass of 1.35 \pm 0.01 M_\sun, which indicates that RS Oph is a progenitor of Type Ia supernovae. We strongly recommend the y-filter observation of novae to detect both the presence of a disk and the hydrogen burning turnoff. Observational data of y magnitudes are provided here together with other multi-wavelength light curve data.