White Dwarfs in Cataclysmic Variables: An Update.

E M Sion,P Godon

doi:10.14311/app.2015.02.0035

Abstract

In this review, we summarize what is currently known about the surface temperatures of accreting white dwarfs in non-magnetic and magnetic cataclysmic variables (CVs) based upon synthetic spectral analyses of far ultraviolet data. We focus only on white dwarf surface temperatures, since in the area of chemical abundances, rotation rates, WD masses and accretion rates, relatively little has changed since our last review, pending the results of a large HST GO program involving 48 CVs of different CV types. The surface temperature of the white dwarf in SS Cygni is re-examined in the light of its revised distance. We also discuss new HST spectra of the recurrent nova T Pyxidis as it transitioned into quiescence following its April 2011 nova outburst.

Highlights

Introductory OverviewThe white dwarfs in cataclysmic variables (hereafter CVWD) are the central engines of the observed outbursts, either as potential wells for the release of gravitational energy during accretion (dwarf nova - DN), or as the sites of explosive thermonuclear runaway (TNR) shell burning (classical novae), steady shell burning (supersoft X-ray binaries) or instantaneous collapse and total thermonuclear detonation if the WD reaches the Chandrasekhar limit (Type Ia supernova? SN Ia)
The white dwarfs in cataclysmic variables are the central engines of the observed outbursts, either as potential wells for the release of gravitational energy during accretion, or as the sites of explosive thermonuclear runaway (TNR) shell burning, steady shell burning or instantaneous collapse and total thermonuclear detonation if the WD reaches the Chandrasekhar limit (Type Ia supernova? SN Ia)
Deeper physical insights require a larger number of chemical abundances, rotation rates, surface temperatures, mass accretion rates, and masses for each spectroscopic subclass of cataclysmic variables (CVs)

Summary

Introductory Overview

The white dwarfs in cataclysmic variables (hereafter CVWD) are the central engines of the observed outbursts, either as potential wells for the release of gravitational energy during accretion (dwarf nova - DN), or as the sites of explosive thermonuclear runaway (TNR) shell burning (classical novae), steady shell burning (supersoft X-ray binaries) or instantaneous collapse and total thermonuclear detonation if the WD reaches the Chandrasekhar limit (Type Ia supernova? SN Ia). Deeper physical insights require a larger number of chemical abundances, rotation rates, surface temperatures, mass accretion rates, and masses for each spectroscopic subclass of CVs. Only can any definitive conclusions be drawn. In order to adequately sample the parameter space (Mwd, i, M , Teff , Porb) of the DNs, Nova-like variables, and magnetic CVs, a large GO program was approved in Cycle 20 (B.Gansicke, Principal Investigator) to secure high quality COS spectra for CV classes underrepresented in the current overall CV sample. In this review our focus is restricted to white dwarf surface temperatures, since in the area of chemical abundances, rotation rates, WD masses and accretion rates, relatively little has changed since our last review in the 2011 Palermo meeting proceedings.

Synthetic Spectral Analysis of FUV Spectra of CVWDs

The White Dwarf in SS Cygni:The VLBI and Corrected Hubble FGS Distance