Comparing the asteroseismic properties of pulsating pre-extremely low mass white dwarf and delta Scuti stars

Abstract

Pulsating extremely low-mass pre-white dwarf stars (pre-ELMV), with masses between ~0.15 Msun and ~0.30 Msun, constitute a new class of variable stars showing g- and possibly p-mode pulsations with periods between 320 and 6000 s, while main sequence delta Scuti stars, with masses between 1.2-2.5 Msun, pulsate in low-order g and p modes with periods in the range [700-28800] s. Interestingly enough, the instability strips of pre-ELM white dwarf and delta Scuti stars nearly overlap in the Teff vs. log g diagram, leading to a degeneracy when spectroscopy is the only tool to classify the stars and pulsation periods only are considered. We employ adiabatic and non-adiabatic pulsation for models of pre-ELM and delta Scuti stars, and compare their pulsation periods, period spacings and rates of period change. We found substantial differences in the periods spacing of delta Scuti and pre-ELM white dwarf models. Even when the same period range is observed, the modes have distinctive signature in the period spacing and period difference values. For instance, the mean period difference of p- modes of consecutive radial orders for delta Scuti model are at least four times longer than the mean period spacing for the pre-ELM white dwarf model in the period range [2000 - 4600] s. In addition, the rate of period change is two orders of magnitudes larger for the pre-ELM white dwarfs compared to delta Scuti stars. In addition, we also report the discovery of a new variable star, SDSSJ075738.94+144827.50, located in the region of the Teff vs. log g diagram where these two kind of stars coexist. The characteristic spacing between modes of consecutive radial orders (p as well as g modes) and the large differences found in the rates of period change for delta Scuti and pre-ELM white dwarf stars suggest that asteroseismology can be employed to discriminate between these two groups of variable stars.

arXiv commentaccepted for publication in Astronomy & Astrophysics

References in corpus (44)

• The Gaia mission
• The Transiting Exoplanet Survey Satellite
• Gaia Data Release 1. Summary of the astrometric, photometric, and survey properties
• Low Temperature Opacities
• The CoRoT satellite in flight : description and performance
• The Kepler characterization of the variability among A- and F-type stars. I. General overview
• 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
• Probing the properties of convective cores through g modes: high-order g modes in SPB and gamma Doradus stars
• New cooling sequences for old white dwarfs
• The formation and evolution of hydrogen-deficient post-AGB white dwarfs: the emerging chemical profile and the expectations for the PG1159-DB-DQ evolutionary connection
• The ELM Survey. I. A Complete Sample of Extremely Low Mass White Dwarfs
• Models of low-mass helium white dwarfs including gravitational settling, thermal and chemical diffusion, and rotational mixing
• Improvements to stellar structure models, based on a grid of 3D convection simulations. II. Calibrating the mixing-length formulation
• Amplitude modulation in $\delta$ Sct stars: statistics from an ensemble study of Kepler targets
• A new asteroseismic diagnostic for internal rotation in $\gamma$ Doradus stars
• Asteroseismic inferences on GW Vir variable stars in the frame of new PG 1159 evolutionary models
• The formation of low-mass helium white dwarfs orbiting pulsars: Evolution of low-mass X-ray binaries below the bifurcation period
• Multi-periodic pulsations of a stripped red giant star in an eclipsing binary
• SDSS J184037.78+642312.3: The First Pulsating Extremely Low Mass White Dwarf
• New nonadiabatic pulsation computations on full PG1159 evolutionary models: the theoretical GW Vir instability strip revisited
• The role of turbulent pressure as a coherent pulsational driving mechanism: the case of the delta Scuti star HD 187547
• A new class of pulsating white dwarf of extremely low mass: the fourth and fifth members
• The ages and colours of cool helium-core white dwarf stars
• That's How We Roll: The NASA K2 Mission Science Products and Their Performance Metrics
• Results of a Search for gamma Dor and delta Sct Stars with the Kepler Spacecraft
• New evolutionary sequences for hot H-deficient white dwarfs on the basis of a full account of progenitor evolution
• Discovery of pulsations, including possible pressure modes, in two new extremely low mass, He-core white dwarfs
• WASP 1628+10 - an EL CVn-type binary with a very-low-mass stripped-red-giant star and multi-periodic pulsations
• PSR J1738+0333: The First Millisecond Pulsar + Pulsating White Dwarf Binary
• The age-metallicity dependence for white dwarfs
• The excitation of solar-like oscillations in a delta Scuti star by efficient envelope convection
• Pruning The ELM Survey: Characterizing Candidate Low-Mass White Dwarfs Through Photometric Variability
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: III. The pre-ELM white dwarf instability strip
• Relationship between low and high frequencies in Delta Scuti stars: Photometric Kepler and spectroscopic analyses of the rapid rotator KIC 8054146
• Discovery of Three Pulsating, Mixed-atmosphere, Extremely Low-mass White Dwarf Precursors
• The Physical Nature of Subdwarf A Stars: White Dwarf Impostors
• The sdA problem I: Physical Properties
• A delta Scuti star in the post-MS contraction phase: 44 Tauri
• Asteroseismic test of rotational mixing in low-mass white dwarfs
• Asteroseismology of hybrid $\delta$ Scuti--$\gamma$ Doradus pulsating stars
• Metal-Rich SX Phe stars in the Kepler Field
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: IV. The secular rate of period change
• Two new pulsating low-mass pre-white dwarfs or SX Phenix stars?*

Cited by in corpus (2)

• The McDonald Observatory search for pulsating sdA stars: asteroseismic support for multiple populations
• An MCMC Approach to the Three-dimensional Structure of the Milky Way Bulge using OGLE-IV $\delta$ Scuti Stars