The evolutionary state of short period magnetic white dwarf binaries

• Published in: arXiv.org 2012-03
• Main Authors: Breedt, E, Gaensicke, B T, Girven, J, Drake, A J, Copperwheat, C M, Parsons, S G, Marsh, T R
• Format: Article
• Language: English
• Subjects: Absorption; Companion stars; Cyclotrons; Deposition; Inclination; Line spectra; Orbits; Radial velocity; Spectrum analysis; White dwarf stars
• ISSN: 2331-8422
• DOI: 10.48550/arxiv.1203.4711

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.