# FUSE Spectroscopy of the Accreting Hot Components in Symbiotic Variables

## TL;DR

This study analyzes far ultraviolet spectra of four symbiotic variables in quiescence to determine the physical properties of their hot components, revealing diverse white dwarf characteristics and accretion features.

## Contribution

It provides detailed spectroscopic analysis of hot components in symbiotic systems, extending wavelength coverage and modeling to better understand their nature and accretion processes.

## Key findings

- RW Hya hosts a low-mass white dwarf at 160,000K.
- CQ Dra's hot component is a small, hot boundary layer at 120,000K.
- EG And contains a low-mass white dwarf at 80-95,000K.

## Abstract

We have conducted a spectroscopic analysis of the far ultraviolet archival spectra of four symbiotic variables, EG And, AE Ara, CQ Dra and RW Hya. RW Hya and EG And have never had a recorded outburst while CQ Dra and AE Ara have outburst histories. We analyze these systems while they are in quiescence in order to help reveal the physical properties of their hot components via comparisons of the observations with optically thick accretion disk models and NLTE model white dwarf photospheres. We have extended the wavelength coverage down to the Lyman Limit with FUSE spectra. We find that the hot component in RW Hya is a low mass white dwarf with a surface temperature of 160,000K. We re-examine whether or not the symbiotic system CQ Dra is a triple system with a red giant transferring matter to a hot component made up of a cataclysmic variable in which the white dwarf has a surface temperature as low as $\sim$20,000K. The very small size of the hot component contributing to the shortest wavelengths of the FUSE spectrum of CQ Dra agrees with an optically thick and geometrically thin ($\sim$4\% of the WD surface) hot ($\sim 120,000$K) boundary layer. Our analysis of EG And reveals that its hot component is a hot, bare, low mass white dwarf with a surface temperature of 80-95,000K, with a surface gravity $\log(g)= 7.5$. For AE Ara, we also find that a low gravity ($\log(g) \sim 6$) hot ($T \sim 130,000$K) WD accounts for the hot component.