SDSS J184037.78+642312.3: The First Pulsating Extremely Low Mass White Dwarf

Abstract

We report the discovery of the first pulsating extremely low mass (ELM) white dwarf (WD), SDSS J184037.78+642312.3 (hereafter J1840). This DA (hydrogen-atmosphere) WD is by far the coolest and the lowest-mass pulsating WD, with Teff = 9100 \pm 170 K and log g = 6.22 \pm 0.06, which corresponds to a mass ~ 0.17 Msun. This low-mass pulsating WD greatly extends the DAV (or ZZ Ceti) instability strip, effectively bridging the log g gap between WDs and main sequence stars. We detect high-amplitude variability in J1840 on timescales exceeding 4000 s, with a non-sinusoidal pulse shape. Our observations also suggest that the variability is multi-periodic. The star is in a 4.6 hr binary with another compact object, most likely another WD. Future, more extensive time-series photometry of this ELM WD offers the first opportunity to probe the interior of a low-mass, presumably He-core WD using the tools of asteroseismology.

5 pages, 3 figures, accepted to ApJ Letters

References in corpus (5)

• Pulsating White Dwarf Stars and Precision Asteroseismology
• The ELM Survey. I. A Complete Sample of Extremely Low Mass White Dwarfs
• The ELM Survey. III. A Successful Targeted Survey for Extremely Low Mass White Dwarfs
• Seismic evidence for non-synchronization in two close sdB+dM binaries from Kepler photometry
• Two New Tidally Distorted White Dwarfs

Cited by in corpus (59)

• A Massive Pulsar in a Compact Relativistic Binary
• Hot subluminous stars
• New evolutionary sequences for extremely low mass white dwarfs: Homogeneous mass and age determinations, and asteroseismic prospects
• New white dwarf and subdwarf stars in the Sloan Digital Sky Survey Data Release 12
• New white dwarf stars in the Sloan Digital Sky Survey Data Release 10
• Pulsating white dwarfs: new insights
• Models of low-mass helium white dwarfs including gravitational settling, thermal and chemical diffusion, and rotational mixing
• The ELM Survey. VII. Orbital Properties of Low Mass White Dwarf Binaries
• Rapid Orbital Decay in the 12.75-minute WD+WD Binary J0651+2844
• Gaia Data Release 3: All-sky classification of 12.4 million variable sources into 25 classes
• The ELM Survey. V. Merging Massive White Dwarf Binaries
• A new class of pulsating white dwarf of extremely low mass: the fourth and fifth members
• Precise Atmospheric Parameters for the Shortest Period Binary White Dwarfs: Gravitational Waves, Metals, and Pulsations
• Asteroseismological study of massive ZZ Ceti stars with fully evolutionary models
• Discovery of pulsations, including possible pressure modes, in two new extremely low mass, He-core white dwarfs
• PSR J1738+0333: The First Millisecond Pulsar + Pulsating White Dwarf Binary
• A Refined Search for Pulsations in White Dwarf Companions to Millisecond Pulsars
• Precise parameters for both white dwarfs in the eclipsing binary CSS 41177
• Gaia Data Release 3: Cross-match of Gaia sources with variable objects from the literature
• Formation of Extremely Low-mass White Dwarfs Binaries
• Pruning The ELM Survey: Characterizing Candidate Low-Mass White Dwarfs Through Photometric Variability
• The seismic properties of low-mass He-core white dwarf stars
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: I. Adiabatic properties
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: III. The pre-ELM white dwarf instability strip
• Discovery of Three Pulsating, Mixed-atmosphere, Extremely Low-mass White Dwarf Precursors
• Sporadic radio pulses from a white dwarf binary at the orbital period
• The sdA problem - II. Photometric and Spectroscopic Follow-up
• The Physical Nature of Subdwarf A Stars: White Dwarf Impostors
• Hydrogen in hot subdwarfs formed by double helium white dwarf mergers
• Short-period $g$-mode pulsations in low-mass white dwarfs triggered by H shell burning
• SDSS J000555.90-100213.5: a hot, magnetic carbon-atmosphere WD rotating with a 2.1 day period
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: II. Nonadiabatic analysis
• LAMOST J0140355+392651: An evolved cataclysmic variable donor transitioning to become an extremely low mass white dwarf
• Probing the structure of Kepler ZZ Ceti stars with full evolutionary models-based asteroseismology
• The coolest extremely low-mass white dwarfs
• Close-in Exoplanets as Candidates of Strange Quark Matter Objects
• Photometric follow-up of 43 new eclipsing white dwarf plus main-sequence binaries from the ZTF survey
• On the existence of warm H-rich pulsating white dwarfs
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: IV. The secular rate of period change
• Discovery of ZZ Cetis in detached white dwarf plus main-sequence binaries
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences VI. Thin H-envelope sequences and asteroseismology of ELMV stars revisited
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: V. Asteroseismology of ELMV white dwarf stars
• Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*
• Pulsating White Dwarfs
• The McDonald Observatory search for pulsating sdA stars: asteroseismic support for multiple populations
• Minute-Cadence Observations of the LAMOST Fields with the TMTS: II. Catalogues of Short-Period Variable Stars from the First Two-Year Surveys
• Time series photometry of the helium atmosphere pulsating white dwarf EC 04207-474
• HST+COS spectra of the double white dwarf CSS 41177 place the secondary inside the pulsational instability strip
• Discovery, TESS Characterization, and Modeling of Pulsations in the Extremely Low Mass White Dwarf GD 278
• Near- and sub-solar-mass naked singularities and black holes from transmutation of white dwarfs
• White Dwarf Variability with gPhoton: Pulsators
• Comparing the asteroseismic properties of pulsating pre-extremely low mass white dwarf and delta Scuti stars
• White Dwarf Stars
• Exploring the pulsational properties of two ZZ Ceti stars
• Asteroseismology of the pulsating extremely low-mass white dwarf SDSS J111215.82+111745.0: a model with $p$-mode pulsations consistent with the observations
• Exploring the internal rotation of the extremely low-mass He-core white dwarf GD 278 with TESS asteroseismology
• Seismic test of the mass-radius relationship of hydrogen-atmospheric white dwarf stars
• A new instability domain of CNO-flashing low-mass He-core stars on their early white-dwarf cooling branches
• Searching for new variable white dwarfs: The discovery of the three new pulsating and three new binary systems