Diagnostics of the Early Explosion Phase of a Classical Nova Using Its X-ray Emission: A Model for the X-ray Outburst of CI Camelopardalis in 1998

TL;DR

This study models the early X-ray emission of a classical nova explosion, revealing the ejected matter's velocity, mass, and the stellar wind's role in producing the observed X-ray outburst of CI Camelopardalis in 1998.

Contribution

It introduces a spherically symmetric model linking nova ejecta interaction with stellar wind to observed X-ray features, providing new estimates of ejected mass and velocity.

Findings

Ejected matter velocity was ~2700 km/s shortly after explosion.

Ejected matter mass estimated at ~10^{-7} to 10^{-6} solar masses.

Stellar wind mass loss rate during outburst was ~(1-2)×10^{-6} solar masses per year.

Abstract

We have computed a spherically symmetric model for the interaction of matter ejected during the outburst of a classical nova with the stellar wind from its optical component.This model is used to describe the intense X-ray outburst (the peak 3-20 keV flux was ~2 Crab) of the binary system CI Camelopardalis in 1998. According to our model, the stellar wind from the optical component heated by a strong shock wave produced when matter is ejected from the white dwarf as the result of a thermonuclear explosion on its surface is the emission source in the standard X-ray band. Comparison of the calculated and observed time dependences of the mean radiation temperature and luminosity of the binary system during its outburst has yielded very important characteristics of the explosion.We have been able to measure the velocity of the ejected matter immediately after the onset of the explosion for the first time: it follows from our model that the ejected matter had a velocity of ~2700 km/s even on 0.1-0.5 day after the outburst onset and it flew with such a velocity for the first 1-1.5 day under an external force, possibly, the radiation pressure from the white dwarf. Subsequently, the matter probably became transparent and began to decelerate. The time dependence of the mean radiation temperature at late expansion phases has allowed us to estimate the mass of the ejected matter, ~10^{-7}-10^{-6} Msun. The mass loss rate in the stellar wind required to explain the observed peak luminosity of the binary system during its outburst has been estimated to be dM/dt ~(1-2)x10^{-6} Msun/yr.