DAHe white dwarfs from the DESI survey

Abstract

A new class of white dwarfs, dubbed DAHe, that present Zeeman-split Balmer lines in emission has recently emerged. However, the physical origin of these emission lines remains unclear. We present here a sample of 21 newly identified DAHe systems and determine magnetic field strengths and (for a subset) periods which span the ranges of ~ 6.5 -- 147 MG and ~ 0.4 -- 36 h respectively. All but four of these systems were identified from the Dark Energy Spectroscopic Instrument (DESI) survey sample of more than 47000 white dwarf candidates observed during its first year of observations. We present detailed analysis of the new DAHe WDJ161634.36+541011.51 with a spin period of 95.3 min, which exhibits an anti-correlation between broadband flux and Balmer line strength that is typically observed for this class of systems. All DAHe systems cluster closely on the Gaia Hertzsprung-Russell diagram where they represent ~ 1 per cent of white dwarfs within that region. This grouping further solidifies their unexplained emergence at relatively late cooling times and we discuss this in context of current formation theories. Nine of the new DAHe systems are identifiable from SDSS spectra of white dwarfs that had been previously classified as featureless DC-type systems. We suggest high S/N, unbiased observations of DCs as a possible route for discovering additional DAHe systems.

19 pages, 10 Figures, accepted for publication in MNRAS

References in corpus (35)

• The Astropy Project: Sustaining and Growing a Community-oriented Open-source Project and the Latest Major Release (v5.0) of the Core Package
• The 2.5 m Telescope of the Sloan Digital Sky Survey
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• The DESI Experiment Part I: Science,Targeting, and Survey Design
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• A gaseous metal disk around a white dwarf
• Magnetic White Dwarfs
• On the Spectral Evolution of Hot White Dwarf Stars. I. A Detailed Model-Atmosphere Analysis of Hot White Dwarfs from SDSS DR12
• New white dwarf stars in the Sloan Digital Sky Survey Data Release 10
• The DESI Experiment Part II: Instrument Design
• Binary Star Origin of High Field Magnetic White Dwarfs
• White Dwarf Rotation as a Function of Mass and a Dichotomy of Mode Linewidths: Kepler Observations of 27 Pulsating DA White Dwarfs Through K2 Campaign 8
• A Giant Planet Candidate Transiting a White Dwarf
• Accretion of a giant planet onto a white dwarf
• Magnetic fields in isolated and interacting white dwarfs
• $Gaia$ white dwarfs within 40 pc II: the volume-limited northern hemisphere sample
• A common origin of magnetism from planets to white dwarfs
• Effective Temperatures of Cataclysmic Variable White Dwarfs as a Probe of their Evolution
• New insight into the magnetism of degenerate stars from the analysis of a volume limited sample of white dwarfs
• A Jovian analogue orbiting a white dwarf star
• Spectroscopic Identification of Cool White Dwarfs in the Solar Neighbourhood
• $\text{Gaia}$ white dwarfs within 40 pc I: spectroscopic observations of new candidates
• The fraction of DA white dwarfs with kilo-Gauss magnetic fields
• Multiple channels for the onset of magnetism in isolated white dwarfs
• $\text{Gaia}$ white dwarfs within 40 pc III: spectroscopic observations of new candidates in the southern hemisphere
• A white dwarf accreting planetary material determined from X-ray observations
• Horizontal spreading of planetary debris accreted by white dwarfs
• Cyclotron modeling phase-resolved infrared spectroscopy of polars I: EF Eridani
• Single magnetic white dwarfs with Balmer emission lines: A small class with consistent physical characteristics as possible signposts for close-in planetary companions
• Magnetic dynamos in white dwarfs -- II. Relating magnetism and pollution
• Survivability of radio-loud planetary cores orbiting white dwarfs
• A test of the planet-star unipolar inductor for magnetic white dwarfs
• Discovery of kilogauss magnetic fields on the nearby white dwarfs WD1105-340 and WD2150+591
• Linking the Interiors and Surfaces of Magnetic Stars
• Discovery of magnetic fields in five DC white dwarfs

Cited by in corpus (5)

• The 40 pc sample of white dwarfs from Gaia
• Two New White Dwarfs With Variable Magnetic Balmer Emission Lines
• An emerging and enigmatic spectral class of isolated DAe white dwarfs
• A GALEX view of the DA White Dwarf Population
• Discovery of Dipolar Chromospheres in Two White Dwarfs