The evolutionary state of short period magnetic white dwarf binaries

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.

15 pages, 12 figures. Accepted for publication in MNRAS

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• The first sub-70 minute non-interacting WD-BD system: EPIC212235321
• Magnetic white dwarfs in post-common-envelope binaries
• Enigmas from the Sloan Digital Sky Survey DR7 Kleinman White Dwarf Catalog
• Signs of accretion in the white dwarf + brown dwarf binary NLTT5306
• X-ray orbital modulation of a white dwarf accreting from an L dwarf: The system SDSS J121209.31+013627.7
• Hydrodynamics and survivability during post-main-sequence planetary engulfment
• New X-ray detections of magnetic period-bounce cataclysmic variables from XMM-Newton and SRG/eROSITA
• A Joint SRG/eROSITA + ZTF Search: Discovery of a 97-min Period Eclipsing Cataclysmic Variable with Evidence of a Brown Dwarf Secondary
• Circular Polarimetry of Suspect Wind-accreting Magnetic pre-Polars
• Cataclysmic variables around the period-bounce: An eROSITA-enhanced multi-wavelength catalog
• The magnetic system SMSS J1606-1000 as a period bouncer
• Cataclysmic Variables in the SUPERBLINK Proper Motion Survey
• eROSITA-selection of new period-bounce Cataclysmic Variables: First follow-up confirmation using TESS and SDSS