Far Ultraviolet Spectroscopy of Three Long Period Nova-Like Variables

TL;DR

This study analyzes far ultraviolet spectra of three long-period nova-like variables using synthetic spectral models, revealing the dominant sources of FUV emission and estimating accretion rates and distances.

Contribution

First synthetic spectral analysis of far ultraviolet spectra for three long-period nova-like variables using advanced accretion disk and white dwarf models.

Findings

V363 Aur and RZ Gru's FUV spectra are consistent with optically thick steady-state accretion disks.

AC Cnc's FUV emission is mainly from a hot white dwarf with a partial contribution from the accretion disk.

Estimated accretion rates and distances are provided and compared with previous literature.

Abstract

We have selected three nova-like variables at the long period extreme of nova-like orbital periods: V363 Aur, RZ Gru and AC Cnc, all with IUE archival far ultraviolet spectra. All are UX UMa type nova-like variables and all have $P_{orb} > 7$h. V363 Aur is a bona fide SW Sex star, and AC Cnc is a probable one, while RZ Gru has not proven to be a member of the SW Sex subclass. We have carried out the first synthetic spectral analysis of far ultraviolet spectra of the three systems using state-of-the-art models both of accretion disks and white dwarf photospheres. We find that the FUV spectral energy distribution of both V363 Aur and RZ Gru are in agreement with optically thick steady state accretion disk models in which the luminous disk accounts for 100% of the FUV light. We present accretion rates and model-derived distances for V363 Aur and RZ Gru. For AC Cnc, we find that a hot accreting white dwarf accounts for $\sim$ 60% of the FUV light with an accretion disk providing the rest. We compare our accretion rates and model-derived distances with estimates in the literature.