Pulsating white dwarfs


Astronomy research
  Software Infrastructure:
     My instruments
  White dwarf supernova:
     Remnant metallicities
     Colliding white dwarfs
     Merging white dwarfs
     Ignition conditions
     Metallicity effects
     Central density effects
     Detonation density effects
     Tracer particle burning
     Subsonic burning fronts
     Supersonic burning fronts
     W7 profiles
  Massive star supernova:
     Rotating progenitors
     3D evolution
     26Al & 60Fe
     44Ti, 60Co & 56Ni
     Yields of radionuclides
     Effects of 12C +12C
     SN 1987A light curve
     Constraints on Ni/Fe ratios
     An r-process
     Compact object IMF
     Neutrino HR diagram
     Pulsating white dwarfs
     Pop III with JWST
     Monte Carlo massive stars
     Neutrinos from pre-SN
     Pre-SN variations
     Monte Carlo white dwarfs
     SAGB stars
     Classical novae
     He shell convection
     Presolar grains
     He burn on neutron stars
     BBFH at 40 years
  Chemical Evolution:
     Iron Pseudocarbynes
     Radionuclides in the 2020s
     Hypatia catalog
     Zone models H to Zn
     Mixing ejecta
     γ-rays within 100 Mpc
  Thermodynamics & Networks
     Stellar EOS
     12C(α,γ)16O Rate
     Proton-rich NSE
     Reaction networks
     Bayesian reaction rates
  Verification Problems:
     Validating an astro code
Software instruments
YouTube: cococubed
Bicycle adventures
Public Outreach
Education materials

AAS Journals
YouTube: AAS
2019 JINA R-process Workshop
2020 Digital Infrastructure
2020 MESA Marketplace
2020 MESA Summer School
2020 ASU Solar Systems
2020 ASU Energy in Everyday Life

Contact: F.X.Timmes
my one page vitae,
full vitae,
research statement, and
teaching statement.
The Impact of White Dwarf Luminosity Profiles on Oscillation Frequencies (2018)

KIC 08626021 is a pulsating DB white dwarf of considerable recent interest, and first of its class to be extensively monitored by Kepler for its pulsation properties. Fitting the observed oscillation frequencies of KIC 08626021 to a model can yield insights into its otherwise-hidden internal structure. Template-based white dwarf models choose a luminosity profile where the luminosity is proportional to the enclosed mass, $L_r \propto M_r$, independent of the effective temperature $T_{\rm eff}$. Evolutionary models of young white dwarfs with $T_{\rm eff} \gtrsim$ 25,000 K suggest neutrino emission gives rise to luminosity profiles with $L_r$ $\not\propto$ $M_r$.

In this article we explore this contrast by comparing the oscillation frequencies between two nearly identical white dwarf models: one with an enforced $L_r \propto M_r$ luminosity profile and the other with a luminosity profile determined by the star's previous evolution history. We find the low order g-mode frequencies differ by up to $\simeq$ 70 $\mu$Hz over the range of Kepler observations for KIC 08626021.

This suggests that by neglecting the proper thermal structure of the star (e.g., accounting for the effect of plasmon neutrino losses), the model frequencies calculated by using an $L_r \propto M_r$ profile may have uncorrected, effectively-random errors at the level of tens of $\mu$Hz. A mean frequency difference of 30 $\mu$Hz, based on linearly extrapolating published results, suggests a template model uncertainty in the fit precision of $\simeq$ 12% in white dwarf mass, $\simeq$ 9% in the radius, and $\simeq$ 3% in the central oxygen mass fraction.


white dwarf structure
propagation diagram
mode frequency differences
weight function shifts
white dwarf cooling