The evolutionary state of short period magnetic white dwarf binaries

TL;DR

This study presents phase-resolved spectroscopy of two new short-period magnetic white dwarf binaries, revealing their orbital characteristics, spectral features, and potential similarities to other known magnetic systems, contributing to understanding their evolutionary states.

Contribution

It introduces two newly identified short-period magnetic white dwarf binaries and analyzes their spectral and orbital properties, expanding knowledge of such systems' evolution.

Findings

Both systems have orbital periods around 86-89 minutes.

Spectral energy distributions show near-infrared excess from cyclotron emission.

High radial velocity amplitudes suggest high orbital inclination.

Abstract

We present phase-resolved spectroscopy of two new short period low accretion rate magnetic binaries, SDSSJ125044.42+154957.3 (Porb = 86 min) and SDSSJ151415.65+074446.5 (Porb = 89 min). Both systems were previously identified as magnetic white dwarfs from the Zeeman splitting of the Balmer absorption lines in their optical spectra. Their spectral energy distributions exhibit a large near-infrared excess, which we interpret as a combination of cyclotron emission and possibly a late type companion star. No absorption features from the companion are seen in our optical spectra. We derive the orbital periods from a narrow, variable H_alpha emission line which we show to originate on the companion star. The high radial velocity amplitude measured in both systems suggests a high orbital inclination, but we find no evidence for eclipses in our data. The two new systems resemble the polar EF Eri in its prolonged low state and also SDSSJ121209.31+013627.7, a known magnetic white dwarf plus possible brown dwarf binary, which was also recovered by our method.