Stellar Evolution in NGC 6791: Mass Loss on the Red Giant Branch and the Formation of Low‐Mass White Dwarfs

Low-mass white dwarfs with helium cores (He-WDs) are known to result from mass loss and/or exchange events in binary systems where the donor is a low mass star evolving along the red giant branch (RGB). Therefore, He-WDs are common components in binary systems with either two white dwarfs or with a white dwarf and a millisecond pulsar (MSP). If the cooling behaviour of He-WDs is known from theoretical studies (see Driebe et al. 1998, and references therein) the ages of MSP systems can be calculated independently of the pulsar properties provided the He-WD mass is known from spectroscopy.

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Jsolated Stars of Low Metallicity

Galaxies ◽

10.3390/galaxies6030089 ◽

2018 ◽

Vol 6 (3) ◽

pp. 89

Author(s):

Efrat Sabach

Keyword(s):

Angular Momentum ◽

Mass Loss ◽

Stellar Evolution ◽

Planetary Nebula ◽

Luminosity Function ◽

Loss Rate ◽

Mass Loss Rate ◽

Solar Metallicity ◽

Low Metallicity ◽

Low Mass

We study the effects of a reduced mass-loss rate on the evolution of low metallicity Jsolated stars, following our earlier classification for angular momentum (J) isolated stars. By using the stellar evolution code MESA we study the evolution with different mass-loss rate efficiencies for stars with low metallicities of Z = 0 . 001 and Z = 0 . 004 , and compare with the evolution with solar metallicity, Z = 0 . 02 . We further study the possibility for late asymptomatic giant branch (AGB)—planet interaction and its possible effects on the properties of the planetary nebula (PN). We find for all metallicities that only with a reduced mass-loss rate an interaction with a low mass companion might take place during the AGB phase of the star. The interaction will most likely shape an elliptical PN. The maximum post-AGB luminosities obtained, both for solar metallicity and low metallicities, reach high values corresponding to the enigmatic finding of the PN luminosity function.

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White Dwarfs

International Astronomical Union Colloquium ◽

10.1017/s0252921100021254 ◽

1994 ◽

Vol 146 ◽

pp. 71-78

Author(s):

Peter Thejll

Keyword(s):

Mass Loss ◽

White Dwarfs ◽

Main Sequence ◽

Asymptotic Giant Branch ◽

List Type ◽

Stellar Core ◽

The Core ◽

Long Time ◽

Red Giant ◽

Carbon Burning

It is the intention of this review to explain what white dwarfs are and why it is interesting to study them, and why the H+2molecule is of special interest.The evolution, from start to finish, of a star of mass less than about 2 solar masses (M⊙), can roughly be summarized as follows:–A cloud of gas contracts from the interstellar medium until hydrogen ignites at the center and amain sequence(MS) star forms. H is transformed to He and the MS phase continues until H is exhausted in the stellar core.–H continues burning in a shell outside the He core while the core contracts. He “ashes” are added to the core, and ared giantstar is formed as the envelope expands. The star evolves up the Red Giant Branch (RGB) (i.e. it becomes more and more luminous and the surface cools).–Towards the end of the RGB phase, mass-loss from the upper layers increases until helium to carbon burning in the core ignites suddenly under degenerate conditions – this is called theHelium Flash(HF). The HF terminates the RGB evolution, and therefore also the mass-loss and the growth of the stellar core.–The star readjusts its structure and the He-core burns steadily on thehorizontal branch(HB) (a phase of nearly-constant luminosity) until fuel is exhausted in the He-core.–Then the C/O core contracts anew and the expansion of the envelope, and the growth of the core, during He-shell burning, mimics RGB evolution but relatively little mass is added to the core this time.–The second ascent of the giant branch (the so-called Asymptotic Giant Branch, or AGB) continues with increased mass loss towards the end–Rapid detachment of a considerable fraction of the remaining envelope and the hot core takes place, sometimes observable as thePlanetary Nebulae(PN) phase.–The PN is dispersed as the core contracts to a white dwarf (WD).–The WD cools for a long time, as internal kinetic energy and latent heat is released.

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Origin and Distributions of White Dwarfs

International Astronomical Union Colloquium ◽

10.1017/s0252921100075965 ◽

1979 ◽

Vol 53 ◽

pp. 206-222 ◽

Cited By ~ 2

Author(s):

W. Weidemann

Keyword(s):

Mass Loss ◽

Stellar Evolution ◽

Final Stage ◽

White Dwarfs ◽

General Scheme ◽

Stellar Atmospheres ◽

Considerable Progress ◽

Surface Gravity ◽

Narrow Strip ◽

Mass Distributions

Today there is no doubt that white dwarfs represent the most common final stage of stellar evolution. Considerable progress has been made during the last decade in our understanding of their origin and distributions. This is reflected by the fact that it is now possible to predict – from basic theory of stellar evolution and stellar atmospheres – the existence of cooling degenerate stars with nearly the observed properties, i.e. a sequence of white dwarfs which fill in their majority a narrow strip in both two-color and color-magnitude diagrams. With other words: the empirically determined surface gravity and radius distributions – which correspond via the mass-radius relation to mass distributions – can now be basically understood within the currently adopted general scheme of stellar evolution with mass loss.

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A CHEOPS white dwarf transit search

Astronomy and Astrophysics ◽

10.1051/0004-6361/202140913 ◽

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.

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Lower Limit for NPN's Masses

Symposium - International Astronomical Union ◽

10.1017/s007418090013894x ◽

1989 ◽

Vol 131 ◽

pp. 454-454

Author(s):

Amos Harpaz

Keyword(s):

Mass Loss ◽

Lower Limit ◽

Planetary Nebula ◽

Mass Range ◽

Lower Mass ◽

Single Star ◽

Star Evolution ◽

Low Mass ◽

Red Giant

The lowest mass observed for a nucleus of a planetary nebula (NPN) is about 0.55 M⊙ (Weidemann and Koester, 1983, Schonberner, 1983). Hence, Lower mass WD's should have been produced without going through the phase of a visible PN ejection. Recently, Harpaz et al. (1987), have shown that very low mass WD's (up to 0.45 M⊙) can be formed by a single star evolution from red giant branch (RGB) stars, due to mass loss along the RGB. It turns out that WD's in mass range of 0.46–0.55 M⊙ formed by a single star evolution should be formed from the AGB, without an observable PN.

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Carbon in the Envelopes of White Dwarfs

International Astronomical Union Colloquium ◽

10.1017/s0252921100075928 ◽

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.

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Mass Distribution and Luminosity Function of White Dwarfs

International Astronomical Union Colloquium ◽

10.1017/s0252921100099255 ◽

1989 ◽

Vol 114 ◽

pp. 1-14 ◽

Cited By ~ 4

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.

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

International Astronomical Union Colloquium ◽

10.1017/s0252921100094987 ◽

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.

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On the formation of hydrogen-deficient low-mass white dwarfs

Astronomy and Astrophysics ◽

10.1051/0004-6361/202037743 ◽

2020 ◽

Vol 638 ◽

pp. A30

Author(s):

Tiara Battich ◽

Leandro G. Althaus ◽

Alejandro H. Córsico

Keyword(s):

White Dwarfs ◽

Evolutionary History ◽

Main Sequence ◽

Asymptotic Giant Branch ◽

Instability Strip ◽

Giant Star ◽

Thermal Pulse ◽

Low Mass ◽

Effective Temperatures ◽

Red Giant

Context. Two of the possible channels for the formation of low-mass (M⋆ ≲ 0.5 M⊙) hydrogen-deficient white dwarfs are the occurrence of a very-late thermal pulse after the asymptotic giant-branch phase or a late helium-flash onset in an almost stripped core of a red giant star. Aims. We aim to asses the potential of asteroseismology to distinguish between the hot flasher and the very-late thermal pulse scenarios for the formation of low-mass hydrogen-deficient white dwarfs. Methods. We computed the evolution of low-mass hydrogen-deficient white dwarfs from the zero-age main sequence in the context of the two evolutionary scenarios. We explore the pulsation properties of the resulting models for effective temperatures characterizing the instability strip of pulsating helium-rich white dwarfs. Results. We find that there are significant differences in the periods and in the period spacings associated with low radial-order (k ≲ 10) gravity modes for white-dwarf models evolving within the instability strip of the hydrogen-deficient white dwarfs. Conclusions. The measurement of the period spacings for pulsation modes with periods shorter than ∼500 s may be used to distinguish between the two scenarios. Moreover, period-to-period asteroseismic fits of low-mass pulsating hydrogen-deficient white dwarfs can help to determine their evolutionary history.

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