Origin of debris disks and the supply of metals in DZ white dwarfs

2007 ◽  
Vol 3 (S249) ◽  
pp. 389-392
Author(s):  
Y. Wang ◽  
R. B. Dong ◽  
D. N. C. Lin ◽  
X. W. Liu
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Dynamical Evolution ◽  
Giant Planets ◽  
Sequence Evolution ◽  
Orbital Eccentricity ◽  
Planetary Bodies ◽  
Compact Disks ◽  
Host Stars ◽  
Gas Drag

AbstractWe discuss the dynamical evolution of minor planetary bodies in the outer regions of planetary systems around the progenitors of DZ white dwarfs. We show that during the planetary-nebula phase of these stars, mass loss can lead to the expansion of all planetary bodies. The orbital eccentricity of the minor bodies, as relics of planetesimals, may be largely excited by the perturbation due to both gas drag effects and nearby gas giant planets. Some of these bodies migrate toward the host star, while others are scattered out of the planetary system. The former have modest probability of being captured by the sweeping secular resonances of giant planets, and induced to migrate toward the host star. When they venture close to their host stars, their orbits are tidally circularized so that they form compact disks where they may undergo further collisionally driven evolution. During the subsequent post main sequence evolution of their host stars, this process may provide an avenue which continually channels heavy elements onto the surface of the white dwarfs. We suggest that this scenario provides an explanation for the recently discovered Calcium line variation in G29-38.

scholarly journals Origin of the dusty disks around white dwarfs

2007 ◽  
Vol 3 (S249) ◽  
pp. 381-384
Author(s):  
R. B. Dong ◽  
Y. Wang ◽  
D. N. C. Lin ◽  
X. W. Liu
Keyword(s):  
Total Mass ◽  
Main Sequence ◽  
Dynamical Evolution ◽  
Central Star ◽  
Orbital Evolution ◽  
Giant Planets ◽  
Mean Motion Resonances ◽  
Host Stars ◽  
Dusty Disks ◽  
Dust Ring

AbstractSome circumstantial evidence for residual planetesimals is constructed based on the recent discovery of a dusty ring around a young white dwarf at the center of the Helix nebula (Suet al. 2007). This ring extends between about 35 and 150 AU from the nebula center, and have a total mass of about 0.13M⊕. In this paper we propose that this ring is the by-product of planets and planetesimals' orbital evolution during the epoch when the central star rapidly lost most of its mass. We examine the dynamical evolution of planetary systems similar to the solar system (i.e. with gas giant planets and residual planetesimals) as their host stars evolve off the main sequence. During the process, some planetesimals will be captured by the gas giants into mean motion resonances and their mutual collisions will form a dust ring similar to that observed at the center of the Helix nebula.

scholarly journals Search for stellar companions of exoplanet host stars by exploring the second ESA-Gaia data release

2019 ◽  
Vol 490 (4) ◽  
pp. 5088-5102 ◽  
Author(s):  
M Mugrauer
Keyword(s):  
Main Sequence ◽  
Stellar Systems ◽  
Sequence Evolution ◽  
The Sun ◽  
M Dwarfs ◽  
Primary Star ◽  
True Nature ◽  
Quadruple System ◽  
Data Release ◽  
Host Stars

ABSTRACT A new survey is presented, which explores the second data release of the ESA-Gaia mission, in order to search for stellar companions of exoplanet host stars, located at distances closer than about 500 pc around the Sun. In total, 176 binaries, 27 hierarchical triples, and one hierarchical quadruple system are detected among more than 1300 exoplanet host stars, whose multiplicity is investigated, yielding a multiplicity rate of the exoplanet host stars of at least about 15  per cent. The detected companions and the exoplanet host stars are equidistant and share a common proper motion, as it is expected for gravitationally bound stellar systems, proven with their accurate Gaia astrometry. The companions exhibit masses in the range between about 0.078 and 1.4 M⊙ with a peak in their mass distribution between 0.15 and $0.3\, \mathrm{M}_{\odot }$. The companions are separated from the exoplanet host stars by about 20 up to 9100 au, but are found most frequently within a projected separation of 1000 au. While most of the detected companions are early M dwarfs, eight white dwarf companions of exoplanet host stars are also identified in this survey, whose true nature is revealed with their photometric properties. Hence, these degenerated companions and the exoplanet host stars form evolved stellar systems with exoplanets, which have survived (physically but also dynamically) the post-main-sequence evolution of their former primary star.

scholarly journals Asteroseismological Probing of the Thermal Evolution of White Dwarf Stars

1992 ◽  
Vol 9 ◽  
pp. 643-645
Author(s):  
G. Fontaine ◽  
F. Wesemael
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Main Sequence ◽  
Thermal Evolution ◽  
Sequence Evolution ◽  
Helium Burning ◽  
Dwarf Stars ◽  
White Dwarf Stars ◽  
The Galaxy ◽  
Low Mass

AbstractIt is generally believed that the immediate progenitors of most white dwarfs are nuclei of planetary nebulae, themselves the products of intermediate- and low-mass main sequence evolution. Stars that begin their lifes with masses less than about 7-8 M⊙ (i.e., the vast majority of them) are expected to become white dwarfs. Among those which have already had the time to become white dwarfs since the formation of the Galaxy, a majority have burnt hydrogen and helium in their interiors. Consequently, most of the mass of a typical white dwarf is contained in a core made of the products of helium burning, mostly carbon and oxygen. The exact proportions of C and 0 are unknown because of uncertainties in the nuclear rates of helium burning.

scholarly journals White dwarfs in the Gaia era

2017 ◽  
Vol 12 (S330) ◽  
pp. 317-320
Author(s):  
P.-E. Tremblay ◽  
N. Gentile-Fusillo ◽  
J. Cummings ◽  
S. Jordan ◽  
B. T. Gänsicke ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Main Sequence ◽  
Milky Way ◽  
Mass Function ◽  
Initial Mass Function ◽  
Sequence Evolution ◽  
Atmospheric Parameters ◽  
Stellar Formation ◽  
Formation History ◽  
Data Release

AbstractThe vast majority of stars will become white dwarfs at the end of the stellar life cycle. These remnants are precise cosmic clocks owing to their well constrained cooling rates. Gaia Data Release 2 is expected to discover hundreds of thousands of white dwarfs, which can then be observed spectroscopically with WEAVE and 4MOST. By employing spectroscopically derived atmospheric parameters combined with Gaia parallaxes, white dwarfs can constrain the stellar formation history in the early developing phases of the Milky Way, the initial mass function in the 1.5 to 8 M⊙ range, and the stellar mass loss as well as the state of planetary systems during the post main-sequence evolution.

scholarly journals Observational problems in determining the ages of open clusters

2008 ◽  
Vol 4 (S258) ◽  
pp. 141-152
Author(s):  
Elizabeth J. Jeffery
Keyword(s):  
White Dwarf ◽  
Main Sequence ◽  
Open Cluster ◽  
Dynamical Evolution ◽  
Stellar Populations ◽  
Statistical Technique ◽  
Open Clusters ◽  
Sequence Evolution ◽  
Data Set ◽  
Wide Range

AbstractOpen clusters have long been objects of interest in astronomy. As a good approximation of essentially pure stellar populations, they have proved very useful for studies in a wide range of astrophysically interesting questions, including stellar evolution and atmospheres, the chemical and dynamical evolution of our Galaxy, and the structure of our Galaxy. Of fundamental importance to our understanding of open clusters is accurate determinations of cluster ages. Currently there are two main techniques for independently determining the ages of stellar populations: main sequence evolution theory (via cluster isochrones) and white dwarf cooling theory. We will provide an overview of these two methods, the current level of agreement between them, as well as a look to the current state of increasing precision in the determination of each. Particularly I will discuss the comprehensive data set collection that is being done by the WIYN Open Cluster Study, as well as a new Bayesian statistical technique that has been developed by our group and its applications in improving and determining white dwarf ages of open clusters. I will review the so-called bright white dwarf technique, a new way of measuring cluster ages with just the bright white dwarfs. I will discuss the first application of the Bayesian technique to the Hyades, also demonstrating the first successful application of the bright white dwarf technique. These results bring the white dwarf age of the Hyades into agreement with the main sequence turn off age for the first time.

scholarly journals Testing planet formation theories with giant stars

2007 ◽  
Vol 3 (S249) ◽  
pp. 209-222
Author(s):  
Luca Pasquini ◽  
M.P. Döllinger ◽  
A. Hatzes ◽  
J. Setiawan ◽  
L. Girardi ◽  
...  
Keyword(s):  
Main Sequence ◽  
Planet Formation ◽  
Mass Range ◽  
Stellar Mass ◽  
Giant Planets ◽  
Main Sequence Stars ◽  
Giant Stars ◽  
Solar Type ◽  
The Subject ◽  
Host Stars

AbstractPlanet searches around evolved giant stars are bringing new insights to planet formation theories by virtue of the broader stellar mass range of the host stars compared to the solar-type stars that have been the subject of most current planet searches programs. These searches among giant stars are producing extremely interesting results. Contrary to main sequence stars planet-hosting giants do not show a tendency of being more metal rich. Even if limited, the statistics also suggest a higher frequency of giant planets (at least 10%) that are more massive compared to solar-type main sequence stars.The interpretation of these results is not straightforward. We propose that the lack of a metallicity-planet connection among giant stars is due to pollution of the star while on the main sequence, followed by dillution during the giant phase. We also suggest that the higher mass and frequency of the planets are due to the higher stellar mass. Even if these results do not favor a specific formation scenario, they suggest that planetary formation might be more complex than what has been proposed so far, perhaps with two mechanisms at work and one or the other dominating according to the stellar mass. We finally stress as the detailed study of the host stars and of the parent sample is essential to derive firm conclusions.

scholarly journals A BINARY SCENARIO FOR THE FORMATION OF STRONGLY MAGNETIZED WHITE DWARFS

2011 ◽  
Vol 20 (supp02) ◽  
pp. 29-36 ◽  
Author(s):  
JASON NORDHAUS
Keyword(s):  
Magnetic Fields ◽  
High Field ◽  
White Dwarfs ◽  
Massive Star ◽  
Main Sequence ◽  
High Mass ◽  
Sequence Evolution ◽  
Main Sequence Stars ◽  
Low Mass ◽  
Initial Discovery

Since their initial discovery, the origin of isolated white dwarfs (WDs) with magnetic fields in excess of ~1 MG has remained a mystery. Recently, the formation of these high-field magnetic WDs has been observationally linked to strong binary interactions incurred during post-main-sequence evolution. Planetary, brown dwarf or stellar companions located within a few AU of main-sequence stars may become engulfed during the primary's expansion off the main sequence. Sufficiently low-mass companions in-spiral inside a common envelope until they are tidally shredded near the natal white dwarf. Formation of an accretion disk from the disrupted companion provides a source of turbulence and shear which act to amplify magnetic fields and transport them to the WD surface. We show that these disk-generated fields explain the observed range of magnetic field strengths for isolated, high-field magnetic WDs. Additionally, we discuss a high-mass binary analogue which generates a strongly-magnetized WD core inside a pre-collapse, massive star. Subsequent core-collapse to a neutron star may produce a magnetar.

scholarly journals The eccentricity distribution of giant planets and their relation to super-Earths in the pebble accretion scenario

2020 ◽  
Vol 643 ◽  
pp. A66
Author(s):  
Bertram Bitsch ◽  
Trifon Trifonov ◽  
Andre Izidoro
Keyword(s):  
Giant Planet ◽  
Planetary Systems ◽  
Dynamical Evolution ◽  
Giant Planets ◽  
Dynamical Structure ◽  
Initial Number ◽  
Orbital Eccentricity ◽  
Eccentric Orbits ◽  
Gas Accretion ◽  
Scattering Events

Observations of the population of cold Jupiter planets (r >1 AU) show that nearly all of these planets orbit their host star on eccentric orbits. For planets up to a few Jupiter masses, eccentric orbits are thought to be the outcome of planet–planet scattering events taking place after gas dispersal. We simulated the growth of planets via pebble and gas accretion as well as the migration of multiple planetary embryos in their gas disc. We then followed the long-term dynamical evolution of our formed planetary system up to 100 Myr after gas disc dispersal. We investigated the importance of the initial number of protoplanetary embryos and different damping rates of eccentricity and inclination during the gas phase for the final configuration of our planetary systems. We constrained our model by comparing the final dynamical structure of our simulated planetary systems to that of observed exoplanet systems. Our results show that the initial number of planetary embryos has only a minor impact on the final orbital eccentricity distribution of the giant planets, as long as the damping of eccentricity and inclination is efficient. If the damping is inefficient (slow), systems with a larger initial number of embryos harbour larger average eccentricities. In addition, for slow damping rates, we observe that scattering events are already common during the gas disc phase and that the giant planets that formed in these simulations match the observed giant planet eccentricity distribution best. These simulations also show that massive giant planets (above Jupiter mass) on eccentric orbits are less likely to host inner super-Earths as they get lost during the scattering phase, while systems with less massive giant planets on nearly circular orbits should harbour systems of inner super-Earths. Finally, our simulations predict that giant planets are not single, on average, but they live in multi-planet systems.

scholarly journals Interacting young M-dwarfs in triple system – Par 1802 binary system case study

2019 ◽  
Vol 489 (2) ◽  
pp. 2298-2306 ◽  
Author(s):  
Shelley J Cheng ◽  
Alec M Vinson ◽  
Smadar Naoz
Keyword(s):  
Mass Transfer ◽  
Binary Systems ◽  
Main Sequence ◽  
Binary Star ◽  
Dynamical Evolution ◽  
Sequence Evolution ◽  
Proof Of Concept ◽  
Orion Nebula ◽  
Roche Limit ◽  
Tidal Heating

ABSTRACT The binary star Par 1802 in the Orion Nebula presents an interesting puzzle in the field of stellar dynamics and evolution. Binary systems such as Par 1802 are thought to form from the same natal material and thus the stellar members are expected to have very similar physical attributes. However, Par 1802’s stars have significantly different temperatures despite their identical (within $3\, {\rm per\, cent}$) masses of about 0.39 M⊙. The leading proof-of-concept idea is that a third companion gravitationally induced the two stars to orbit closer than their Roche limit, which facilitated heating through tidal effects. Here we expand on this idea and study the three-body dynamical evolution of such a system, including tidal and pre-main-sequence evolution. We also include tidal heating and mass transfer at the onset of Roche limit crossing. We show, as a proof-of-concept, that mass transfer combined with tidal heating can naturally explain the observed temperature discrepancy. We also predict the orbital configuration of the possible tertiary companion. Finally, we suggest that the dynamical evolution of such a system has pervasive consequences. We expect an abundance of systems to undergo mass transfer during their pre-main-sequence time, which can cause temperature differences.

scholarly journals Constraining planet formation around 6–8 M⊙ stars

2020 ◽  
Vol 493 (1) ◽  
pp. 765-775 ◽  
Author(s):  
Dimitri Veras ◽  
Pier-Emmanuel Tremblay ◽  
J J Hermes ◽  
Catriona H McDonald ◽  
Grant M Kennedy ◽  
...  
Keyword(s):  
White Dwarf ◽  
White Dwarfs ◽  
Main Sequence ◽  
Planet Formation ◽  
Mass Range ◽  
Minor Planets ◽  
Spectroscopic Analyses ◽  
M Stars ◽  
Host Stars ◽  
Rubble Pile

ABSTRACT Identifying planets around O-type and B-type stars is inherently difficult; the most massive known planet host has a mass of only about $3\, \mathrm{M}_{\odot }$. However, planetary systems which survive the transformation of their host stars into white dwarfs can be detected via photospheric trace metals, circumstellar dusty and gaseous discs, and transits of planetary debris crossing our line of sight. These signatures offer the potential to explore the efficiency of planet formation for host stars with masses up to the core-collapse boundary at $\approx 8\, \mathrm{M}_{\odot }$, a mass regime rarely investigated in planet formation theory. Here, we establish limits on where both major and minor planets must reside around $\approx 6\rm {-}8\, \mathrm{M}_{\odot }$ stars in order to survive into the white dwarf phase. For this mass range, we find that intact terrestrial or giant planets need to leave the main sequence beyond approximate minimum star–planet separations of, respectively, about 3 and 6 au. In these systems, rubble pile minor planets of radii 10, 1.0, and 0.1 km would have been shorn apart by giant branch radiative YORP spin-up if they formed and remained within, respectively, tens, hundreds, and thousands of au. These boundary values would help distinguish the nature of the progenitor of metal pollution in white dwarf atmospheres. We find that planet formation around the highest mass white dwarf progenitors may be feasible, and hence encourage both dedicated planet formation investigations for these systems and spectroscopic analyses of the highest mass white dwarfs.

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