A catalog of 159,238 white dwarf ages

2019 ◽  
Vol 15 (S357) ◽  
pp. 188-191
Author(s):  
Ted von Hippel ◽  
Adam Moss ◽  
Isabelle Kloc ◽  
Natalie Moticska ◽  
Jimmy Sargent ◽  
...  
Keyword(s):  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Stellar Mass ◽  
Posterior Distributions ◽  
Trigonometric Parallaxes ◽  
On Line ◽  
Better Than

AbstractWe employ Pan-STARRS photometry, Gaia trigonometric parallaxes, modern stellar evolution and atmosphere models, and our Bayesian fitting approach to determine cooling and total ages for 159,238 white dwarfs. In many cases we are able to derive precise ages (better than 5%) for individual white dwarfs. These results are meant for broad use within the white dwarf and stellar astrophysics communities and we plan to make available on-line the posterior distributions for cooling age, total age, initial stellar mass, and other parameters.

scholarly journals White Dwarf Evolution in Real Time: What Pulsating White Dwarfs Teach us About Stellar Evolution

1989 ◽  
Vol 114 ◽  
pp. 97-108 ◽  
Author(s):  
Steven D. Kawaler ◽  
Carl J. Hansen
Keyword(s):  
Real Time ◽  
Structural Properties ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Recent Progress ◽  
Short Review ◽  
Observational Constraints ◽  
Made In

The variable white dwarfs repeatedly force theory to conform to their observed properties so that further progress can be made in understanding the structure and evolution of all white dwarfs. We use the term “understanding” in a loose sense here because, as we will show, both observational constraints and interpretation of the observations vis-à-vis theory contribute to uncertainties in our understanding at this time. In any case, recent progress in this field (sometimes called white dwarf seismology) has provided some fascinating insights into the evolutionary and structural properties of white dwarfs and their progenitors. This short review is our attempt to describe recent progress made in the interaction of theory with observations.

scholarly journals An Example Demonstrating the Potential for Asteroseismology of DB White Dwarf Stars

1993 ◽  
Vol 139 ◽  
pp. 116-116
Author(s):  
P.A. Bradley ◽  
M.A. Wood
Keyword(s):  
Internal Structure ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Galactic Disk ◽  
Helium Surface ◽  
Dwarf Stars ◽  
University Of Texas ◽  
White Dwarf Stars ◽  
History Of

AbstractWe present the results of a parametric survey of evolutionary models of compositionally stratified white dwarfs with helium surface layers (DB white dwarfs). Because white dwarfs are the most common final end state of stellar evolution, determining their internal structure will offer us many clues about stellar evolution, the physics of matter under extreme conditions, plus the history of star formation and age of the local Galactic disk. As a first step towards determining the internal structure of DB white dwarf stars, we provide a comprehensive set of theoretical g-mode pulsation periods for comparison to observations.Because DB white dwarfs have a layered structure consisting of a helium layer overlying the carbon/oxygen core, some modes will have the same wavelength as the thickness of the helium layer, allowing a resonance to form. This resonance is called mode trapping (see Brassard et al. 1992 and references therein) and has directly observable consequences, because modes at or near the resonance have eigenfunctions and pulsation periods that are similar to each other. This results in much smaller period spacings between consecutive overtone modes of the same spherical harmonic index than the uniform period spacings seen between non-trapped modes. We demonstrate with an example how one can use the distribution of pulsation periods to determine the total stellar mass, the mass of the helium surface layer, and the extent of the helium/carbon and carbon/oxygen transition zones. With these tools, we have the prospect of being able to determine the structure of the observed DBV white dwarfs, once the requisite observations become available.We are grateful to C.J. Hansen, S.D. Kawaler, R.E. Nather, and D.E. Winget for their encouragement and many discussions. This research was supported by the National Science Foundation under grants 85-52457 and 90-14655 through the University of Texas and McDonald Observatory.

scholarly journals A CHEOPS white dwarf transit search

2021 ◽  
Vol 651 ◽  
pp. L12
Author(s):  
Brett M. Morris ◽  
Kevin Heng ◽  
Alexis Brandeker ◽  
Andrew Swan ◽  
Monika Lendl
Keyword(s):  
Stellar Evolution ◽  
Point Spread Function ◽  
White Dwarf ◽  
Metal Pollution ◽  
White Dwarfs ◽  
Point Spread ◽  
Spread Function ◽  
Data Products ◽  
Red Giant

White dwarf spectroscopy shows that nearly half of white dwarf atmospheres contain metals that must have been accreted from planetary material that survived the red giant phases of stellar evolution. We can use metal pollution in white dwarf atmospheres as flags, signalling recent accretion, in order to prioritize an efficient sample of white dwarfs to search for transiting material. We present a search for planetesimals orbiting six nearby white dwarfs with the CHaracterising ExOPlanet Satellite (CHEOPS). The targets are relatively faint for CHEOPS, 11 mag < G < 12.8 mag. We used aperture photometry data products from the CHEOPS mission as well as custom point-spread function photometry to search for periodic variations in flux due to transiting planetesimals. We detect no significant variations in flux that cannot be attributed to spacecraft systematics, despite reaching a photometric precision of < 2 ppt in 60 s exposures on each target. We simulate observations to show that the small survey is sensitive primarily to Moon-sized transiting objects with periods between 3 h < P < 10 h, with radii of R ≳ 1000 km.

scholarly journals Carbon in the Envelopes of White Dwarfs

1979 ◽  
Vol 53 ◽  
pp. 188-191
Author(s):  
Francesca D’Antona
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Current Theory ◽  
Core Mass ◽  
Maximum Extension ◽  
Nuclear Burning ◽  
Remnant Mass

Current theory of stellar evolution predicts that stars of initial masses up to 4-6 M⊙ evolve into Carbon-Oxygen White Dwarfs surrounded by a Helium envelope and, possibly, by a Hydrogen envelope. It also predicts that the mass of the Helium envelope which remains on the star at the end of its double shell burning evolution is a function of the Carbon-Oxygen core mass (Paczynski 1975). It can be shown that this mass can be reduced – but only slightly – during the following evolution of the star towards the White Dwarf region, either by nuclear burning or by mass loss (D’Antona and Mazzitelli 1979). During the White Dwarf stage, Helium convection grows into White Dwarfs having Helium atmospheres. The maximum extension of Helium convective mass is a function of the mass of the star (Fontaine and Van Horn 1976; D’Antona and Mazzitelli 1975,1979). It turns out that the Helium envelope remnant mass is always at least three orders of magnitude larger than the maximum Helium convective mass, whatever the mass of the star may be. This statement is unlikely to be changed by refinements either in the theory of double shell burning or in the theory of White Dwarf envelope convection.

scholarly journals The effects of boundary conditions on stellar evolution

1987 ◽  
Vol 122 ◽  
pp. 463-464
Author(s):  
Amos Harpaz ◽  
Attay Kovetz ◽  
Giora Shaviv
Keyword(s):  
Boundary Conditions ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Surface Boundary ◽  
Surface Boundary Conditions

The effects of using different treatments of the surface boundary conditions are investigated in the context of the mass of He White Dwarfs. We find that since the White Dwarf progenitor is a star with a very extended atmosphere, the results are sensitive to the degree of accuracy implemented in the handling of the boundary conditions.

scholarly journals Mass Distribution and Luminosity Function of White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 1-14 ◽  
Author(s):  
Volker Weidemann ◽  
Jie W. Yuan
Keyword(s):  
Mass Loss ◽  
Mass Distribution ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Luminosity Function ◽  
Present Situation ◽  
Single Well ◽  
Mass Dispersion

Ever since Graham’s Strömgren photometry (1972) demonstrated the existence of a single well defined cooling sequence of DA white dwarfs the question of the mass dispersion (or the width of the number-mass distribution) has been in the foreground of my studies (Weidemann, 1970, 1977).Indeed it turned out that the shape of the white dwarf mass distribution provides strong constraints on the theory of stellar evolution with mass loss, a fact which will be demonstrated again in the following lecture. It therefore seems worthwhile to dwell in some detail on the methods of its determination. For the benefit of the non-specialists I shall first present some of the historical results and then continue to discuss the present situation.

scholarly journals Comments on ‘numerical stability of detonations in white dwarf simulations’

2019 ◽  
Vol 491 (3) ◽  
pp. 3760-3766 ◽  
Author(s):  
Doron Kushnir ◽  
Boaz Katz
Keyword(s):  
Boundary Conditions ◽  
White Dwarf ◽  
Numerical Stability ◽  
White Dwarfs ◽  
Test Problem ◽  
Slow Convergence ◽  
One Dimensional ◽  
Better Than

ABSTRACT Katz & Zingale (KZ19) recently studied a one-dimensional test problem, intended to mimic the process of detonation ignition in head-on collisions of two carbon–oxygen (CO) white dwarfs. They do not obtain ignition of a detonation in pure CO compositions unless the temperature is artificially increased or $5{{\ \rm per\ cent}}$ He is included. In both of these cases they obtain converged ignition only for spatial resolutions better than $0.1\, \textrm{km}$, which are beyond the capability of multidimensional simulations. This is in a contradiction with the claims of Kushnir et al. (K13) that a convergence to $\mathord {\sim}10{{\ \rm per\ cent}}$ is achieved for a resolution of a few km. Using Eulerian and Lagrangian codes we show that a converged and resolved ignition is obtained for pure CO in this test problem without the need for He or increasing the temperature. The two codes agree to within $1{{\ \rm per\ cent}}$ and convergence is obtained at resolutions of several km. We calculate the case that includes He and obtain a similar slow convergence, but find that it is due to a boundary numerical artefact that can (and should) be avoided. Correcting the boundary conditions allows convergence with resolution of ${\sim}10\, \textrm{km}$ in an agreement with the claims of K13. It is likely that the slow convergence obtained by KZ19 in this case is because of a similar boundary numerical artefact, but we are unable to verify this. KZ19 further recommended to avoid the use of the burning limiter introduced by K13. We show that their recommendation is not justified.

scholarly journals The initial/final mass relation for stellar evolution with mass loss

1981 ◽  
Vol 59 ◽  
pp. 339-344
Author(s):  
Volker Weidemann
Keyword(s):  
Mass Loss ◽  
Stellar Evolution ◽  
White Dwarf ◽  
Empirical Data ◽  
Planetary Nebula ◽  
White Dwarfs ◽  
Planetary Nebulae ◽  
Universal Relation ◽  
Mass Relation ◽  
Theoretical Concepts

The relation between initial and final masses is discussed under consideration of changing theoretical concepts and new empirical data on masses of white dwarfs and nuclei of planetary nebulae. It is concluded that presently adopted schemes of evolution need revision, and that no universal relation exists.The strongest evidence for large amounts of mass loss during stellar evolution has been provided by the existence of white dwarfs – with masses typically of 0.6 m (m = M/Mʘ), much below the galactic turn-off masses – and by the phenomenon of planetary nebula production before a star descends into the white dwarf region.

scholarly journals Forever young white dwarfs: when stellar ageing stops

2020 ◽  
Author(s):  
Maria Camisassa ◽  
Leandro Althaus ◽  
Santiago Torres ◽  
Alejandro Córsico ◽  
Sihao Cheng ◽  
...  
Keyword(s):  
Energy Source ◽  
Stellar Evolution ◽  
White Dwarf ◽  
White Dwarfs ◽  
Space Mission ◽  
Dwarf Stars ◽  
End Point ◽  
White Dwarf Stars ◽  
Single Standard ◽  
Stellar Mergers

Abstract White dwarf stars are the most common end point of stellar evolution. In particular, ultra-massive white dwarfs are expected to harbour oxygen-neon (ONe) cores as a result of single standard stellar evolution. However, a fraction of them could have carbon-oxygen (CO) cores and be born as a result of merger events. Recent observations provided by Gaia space mission, indicate that a fraction of the ultra-massive white dwarfs experience a strong delay in their cooling, which cannot be attributed only to the occurrence of crystallization, thus requiring an unknown energy source able to prolong their life for long periods of time. Here, we show that the energy released by 22Ne sedimentation in ultra-massive white dwarfs with CO cores is at the root of the long cooling delay of these stars. Our results provide solid sustain to the existence of CO-core ultra-massive white dwarfs and the occurrence of stellar mergers.

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