A new class of pulsating hot subdwarfs

Abstract

Using high-cadence observations from the Zwicky Transient Facility at low Galactic latitudes, we have discovered a new class of pulsating, hot, compact stars. We have found four candidates, exhibiting blue colors ($g-r\le -0.1$ mag), pulsation amplitudes of $>5\%$, and pulsation periods of $200-475$ sec. Fourier transforms of the lightcurves show only one dominant frequency. Phase-resolved spectroscopy for three objects reveals significant radial velocity, T${}_{\mathrm{eff}}$ and log(g) variations over the pulsation cycle, consistent with large amplitude radial oscillations. The mean T${}_{\mathrm{eff}}$ and log(g) for these stars are consistent with hot subdwarf B (sdB) effective temperatures and surface gravities. We calculate evolutionary tracks using MESA and adiabatic pulsations using GYRE for low-mass helium-core pre-white dwarfs and low mass helium-burning stars. Comparison of low-order radial oscillation mode periods with the observed pulsation periods show better agreement with the pre-white dwarf models. Therefore, we suggest that these new pulsators and Blue Large-Amplitude Pulsators (BLAPs) could be members of the same class of pulsators, composed of young $\approx 0.25-0.35$ M${}_{\odot }$ helium-core pre-white dwarfs.

arXiv commentaccepted for publication in ApJL, 9 pages, 3 figures and 2 tables

References in corpus (35)

• Astropy: A Community Python Package for Astronomy
• Gaia Data Release 2. Summary of the contents and survey properties
• Modules for Experiments in Stellar Astrophysics (MESA)
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• Modules for Experiments in Stellar Astrophysics (MESA): Giant Planets, Oscillations, Rotation, and Massive Stars
• Modules for Experiments in Stellar Astrophysics (MESA): Binaries, Pulsations, and Explosions
• Modules for Experiments in Stellar Astrophysics (MESA): Convective Boundaries, Element Diffusion, and Massive Star Explosions
• The Zwicky Transient Facility: System Overview, Performance, and First Results
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• The Zwicky Transient Facility: Data Processing, Products, and Archive
• Las Cumbres Observatory Global Telescope Network
• The Zwicky Transient Facility: Science Objectives
• GYRE: An open-source stellar oscillation code based on a new Magnus Multiple Shooting Scheme
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• Hot subluminous stars
• The Zwicky Transient Facility: Surveys and Scheduler
• Periodograms for Multiband Astronomical Time Series
• The Potential of Asteroseismology for Hot, Subdwarf B Stars: A New Class of Pulsating Stars?
• Close binary EHB stars from SPY
• First Kepler results on compact pulsators I. Survey target selection and the first pulsators
• The population of hot subdwarf stars studied with Gaia II. The Gaia DR2 catalogue of hot subluminous stars
• Multi-periodic pulsations of a stripped red giant star in an eclipsing binary
• Abundance studies of sdB stars using UV echelle HST/STIS spectroscopy
• Blue large-amplitude pulsators as a new class of variable stars
• CHIMERA: a wide-field, multi-color, high-speed photometer at the prime focus of the Hale telescope
• Using conditional entropy to identify periodicity
• WASP 1628+10 - an EL CVn-type binary with a very-low-mass stripped-red-giant star and multi-periodic pulsations
• 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
• On the evolutionary status and pulsations of the recently discovered Blue Large-Amplitude Pulsators (BLAPs)
• Post-common-envelope binary stars, radiative levitation, and blue large-amplitude pulsators
• Photometry and spectroscopy of the new sdBV CS 1246
• Pulsating low-mass white dwarfs in the frame of new evolutionary sequences: IV. The secular rate of period change
• A Model of the Pulsating Extremely Low-Mass White Dwarf Precursor WASP 0247-25B
• Blue Large-Amplitude Pulsators (BLAPs): possible origin, evolutionary status, and nature of their pulsations

Cited by in corpus (29)

• A systematic search of Zwicky Transient Facility data for ultracompact binary LISA-detectable gravitational-wave sources
• Hot subdwarfs in close binaries observed from space I: orbital, atmospheric, and absolute parameters and the nature of their companions
• Year 1 of the ZTF high-cadence Galactic Plane Survey: Strategy, goals, and early results on new single-mode hot subdwarf B-star pulsators
• Hot subdwarf Atmospheric parameters, Kinematics, and Origins -- Based on 1587 hot subdwarf stars observed in Gaia DR2 and LAMOST DR7
• Pulsation in faint blue stars
• The ZTF Source Classification Project: I. Methods and Infrastructure
• A Systematic Search for Short-period Close White Dwarf Binary Candidates Based on Gaia EDR3 Catalog and Zwicky Transient Facility Data
• The ZTF Source Classification Project: II. Periodicity and variability processing metrics
• Binary evolution pathways of Blue Large-Amplitude Pulsators
• Blue Large-Amplitude Pulsators: the Possible Surviving Companions of Type Ia Supernovae
• Shell helium-burning hot subdwarf B stars as candidates for blue large-amplitude pulsators
• Hot subdwarfs in close binaries observed from space II: Analysis of the light curves
• HD 133729: A blue large-amplitude pulsator in orbit around a main-sequence B-type star
• Identifying Blue Large Amplitude Pulsators from Gaia DR2 & ZTF DR3
• An 18.9-minute Blue Large-Amplitude Pulsator Crossing the 'Hertzsprung Gap' of Hot Subdwarfs
• The OmegaWhite Survey for Short-Period Variable Stars VII: High amplitude, short period blue variables
• Minute-Cadence Observations of the LAMOST Fields with the TMTS: II. Catalogues of Short-Period Variable Stars from the First Two-Year Surveys
• EVR-CB-004: An Inflated Hot Subdwarf O star + Unseen WD Companion in a Compact Binary Discovered with the Evryscope
• Confirmation of Monoperiodicity Above 20 Seconds for Two Blue Large-Amplitude Pulsators
• Uncovering the chemical structure of the pulsating low-mass white dwarf SDSS J115219.99+024814.4
• Observational Parameters of Blue Large-amplitude Pulsators
• Discovery of periodic variables in the hot subdwarf catalogue through a systematic search in Zwicky Transient Facility data
• Binary Evolution Pathways to Blue Large-Amplitude Pulsators: Insights from HD 133729
• The oscillation properties of the Blue Large Amplitude Pulsators (BLAPs): relative change rate of periods, excitations, and period relations
• A new instability domain of CNO-flashing low-mass He-core stars on their early white-dwarf cooling branches
• Multi-messenger parameter inference of gravitational-wave and electromagnetic observations of white dwarf binaries
• Hot subdwarfs from the surviving companions of the white dwarf + main-sequence channel of Type Ia supernovae
• Spectroscopic follow-up of hot subdwarf variables found in ZTF -- Atmospheric and fundamental properties of radial-mode sdB pulsators
• Improved hydrodynamic pulsation models for the pulsating extreme helium star V652 Herculis