Revised analysis of the supersoft X-ray phase, helium enrichment, and turn-off time in the 2000 outburst of the recurrent nova CI Aquilae

TL;DR

This study models the 2000 outburst of recurrent nova CI Aquilae, estimating the white dwarf mass, helium enrichment, and the duration of the supersoft X-ray phase using optically thick wind theory, and compares it with historical data.

Contribution

It provides a revised analysis of the nova's outburst, estimating key parameters and the X-ray phase duration based on theoretical modeling and light curve fitting.

Findings

White dwarf mass estimated at 1.2 solar masses

Supersoft X-ray source phase lasted 150 days

Helium enrichment in ejecta is approximately He/H ~ 0.5

Abstract

The recurrent nova CI Aquilae entered the final decline phase a bit before May of 2001, showing the slowest evolution among the recurrent novae. Based on the optically thick wind mass-loss theory of the thermonuclear runaway model, we have estimated the turn-off time of the CI Aql 2000 outburst in March of 2001, after a supersoft X-ray source (SSS) phase lasts 150 days from December of 2000 until May of 2001. Fitting our theoretical light curves with both the 1917 and 2000 outbursts, we also obtained the WD mass to be M_{WD}= 1.2 \pm 0.05 M_\sun, helium enrichment of ejecta, He/H ~ 0.5 by number, the mass of the hydrogen-rich envelope on the WD of \Delta M ~ 6 x 10^{-6} M_\sun at the optical maximum, which is indicating an average mass accretion rate of \dot M_{acc} ~ 0.8 x 10^{-7} M_\sun yr^{-1} during the quiescent phase between the 1917 and 2000 outbursts.