scholarly journals Are exoplanetesimals differentiated?

2020 ◽  
Vol 492 (2) ◽  
pp. 2683-2697 ◽  
Author(s):  
Amy Bonsor ◽  
Philip J Carter ◽  
Mark Hollands ◽  
Boris T Gänsicke ◽  
Zoë Leinhardt ◽  
...  
Keyword(s):  
White Dwarfs ◽  
Planetary Systems ◽  
Mantle Material ◽  
Planetary Body ◽  
Single Body ◽  
Exoplanetary Systems ◽  
Large Numbers ◽  
Metal Abundances ◽  
Larger Sample ◽  
Collisional Evolution

ABSTRACT Metals observed in the atmospheres of white dwarfs suggest that many have recently accreted planetary bodies. In some cases, the compositions observed suggest the accretion of material dominantly from the core (or the mantle) of a differentiated planetary body. Collisions between differentiated exoplanetesimalrrs produce such fragments. In this work, we take advantage of the large numbers of white dwarfs where at least one siderophile (core-loving) and one lithophile (rock-loving) species have been detected to assess how commonly exoplanetesimals differentiate. We utilize N-body simulations that track the fate of core and mantle material during the collisional evolution of planetary systems to show that most remnants of differentiated planetesimals retain core fractions similar to their parents, while some are extremely core rich or mantle rich. Comparison with the white dwarf data for calcium and iron indicates that the data are consistent with a model in which $66^{+4}_{-6}{{\ \rm per\ cent}}$ have accreted the remnants of differentiated planetesimals, while $31^{+5}_{-5}{{\ \rm per\ cent}}$ have Ca/Fe abundances altered by the effects of heating (although the former can be as high as $100{{\ \rm per\ cent}}$, if heating is ignored). These conclusions assume pollution by a single body and that collisional evolution retains similar features across diverse planetary systems. These results imply that both collisions and differentiation are key processes in exoplanetary systems. We highlight the need for a larger sample of polluted white dwarfs with precisely determined metal abundances to better understand the process of differentiation in exoplanetary systems.

scholarly journals Exogeology from Polluted White Dwarfs

Elements ◽  
2021 ◽  
Vol 17 (4) ◽  
pp. 241-244
Author(s):  
Siyi Xu ◽  
Amy Bonsor
Keyword(s):  
Solar System ◽  
White Dwarf ◽  
White Dwarfs ◽  
Planetary Systems ◽  
Terrestrial Planets ◽  
Strong Gravity ◽  
Exoplanetary Systems ◽  
Planetary Bodies

It is difficult to study the interiors of terrestrial planets in the Solar System and the problem is magnified for distant exoplanets. However, sometimes nature is helpful. Some planetary bodies are torn to fragments and consumed by the strong gravity close to the descendants of Sun-like stars, white dwarfs. We can deduce the general composition of the planet when we observe the spectroscopic signature of the white dwarf. Most planetary fragments that fall into white dwarfs appear to be rocky with a variable fraction of associated ice and carbon. These white dwarf planetary systems provide a unique opportunity to study the geology of exoplanetary systems.

scholarly journals Bayesian constraints on the origin and geology of exo-planetary material using a population of externally polluted white dwarfs

2021 ◽  
Author(s):  
John H D Harrison ◽  
Amy Bonsor ◽  
Mihkel Kama ◽  
Andrew M Buchan ◽  
Simon Blouin ◽  
...  
Keyword(s):  
Solar System ◽  
White Dwarf ◽  
Bayesian Model ◽  
Total Mass ◽  
White Dwarfs ◽  
Bulk Composition ◽  
Planetary Systems ◽  
The Moon ◽  
Planetary Bodies ◽  
Nearby Stars

Abstract White dwarfs that have accreted planetary bodies are a powerful probe of the bulk composition of exoplanetary material. In this paper, we present a Bayesian model to explain the abundances observed in the atmospheres of 202 DZ white dwarfs by considering the heating, geochemical differentiation, and collisional processes experienced by the planetary bodies accreted, as well as gravitational sinking. The majority (>60%) of systems are consistent with the accretion of primitive material. We attribute the small spread in refractory abundances observed to a similar spread in the initial planet-forming material, as seen in the compositions of nearby stars. A range in Na abundances in the pollutant material is attributed to a range in formation temperatures from below 1,000 K to higher than 1,400 K, suggesting that pollutant material arrives in white dwarf atmospheres from a variety of radial locations. We also find that Solar System-like differentiation is common place in exo-planetary systems. Extreme siderophile (Fe, Ni or Cr) abundances in 8 systems require the accretion of a core-rich fragment of a larger differentiated body to at least a 3σ significance, whilst one system shows evidence that it accreted a crust-rich fragment. In systems where the abundances suggest that accretion has finished (13/202), the total mass accreted can be calculated. The 13 systems are estimated to have accreted masses ranging from the mass of the Moon to half that of Vesta. Our analysis suggests that accretion continues for 11Myrs on average.

The Effect of CNO Metal Abundances on the Soft X-Ray Emission from He Rich White Dwarfs

1989 ◽  
Vol 114 ◽  
pp. 202-205
Author(s):  
M.A. Barstow
Keyword(s):  
Effective Temperature ◽  
Planetary Nebula ◽  
White Dwarfs ◽  
X Ray ◽  
Metal Abundances

AbstractPredicted soft X-ray fluxes for model atmospheres containing varying concentrations of CNO metals are compared with those observed by EXOSAT for the planetary nebula nucleus K1-16. An effective temperature in the range ≈ 125000 − 180000K is determined for K1-16 and a limit on the concentration of CNO in the atmosphere (between 0.02 and 20 ×solar relative to He) obtained. Some comments on the application of the models to the apparently metal rich star H1504+65 are included.

Metal abundances in the hot DA white dwarfs Wolf 1346 and Feige 24

1984 ◽  
Vol 287 ◽  
pp. 868 ◽  
Author(s):  
F. Wesemael ◽  
R. B. C. Henry ◽  
H. L. Shipman
Keyword(s):  
White Dwarfs ◽  
Metal Abundances

scholarly journals Searching for a dusty cometary belt around TRAPPIST-1 with ALMA

2020 ◽  
Vol 492 (4) ◽  
pp. 6067-6073 ◽  
Author(s):  
S Marino ◽  
M C Wyatt ◽  
G M Kennedy ◽  
M Kama ◽  
L Matrà ◽  
...  
Keyword(s):  
Liquid Water ◽  
Kuiper Belt ◽  
Dust Emission ◽  
Planetary Systems ◽  
Dynamical Instability ◽  
Solid Mass ◽  
Low Mass Stars ◽  
Upper Limit ◽  
Low Mass ◽  
Collisional Evolution

ABSTRACT Low-mass stars might offer today the best opportunities to detect and characterize planetary systems, especially those harbouring close-in low-mass temperate planets. Among those stars, TRAPPIST-1 is exceptional since it has seven Earth-sized planets, of which three could sustain liquid water on their surfaces. Here we present new and deep ALMA observations of TRAPPIST-1 to look for an exo-Kuiper belt which can provide clues about the formation and architecture of this system. Our observations at 0.88 mm did not detect dust emission, but can place an upper limit of 23 µJy if the belt is smaller than 4 au, and 0.15 mJy if resolved and 100 au in radius. These limits correspond to low dust masses of ∼10−5 to 10−2 M⊕, which are expected after 8 Gyr of collisional evolution unless the system was born with a >20 M⊕ belt of 100 km-sized planetesimals beyond 40 au or suffered a dynamical instability. This 20 M⊕ mass upper limit is comparable to the combined mass in TRAPPIST-1 planets, thus it is possible that most of the available solid mass in this system was used to form the known planets. A similar analysis of the ALMA data on Proxima Cen leads us to conclude that a belt born with a mass ≳1 M⊕ in 100 km-sized planetesimals could explain its putative outer belt at 30 au. We recommend that future characterizations of debris discs around low-mass stars should focus on nearby and young systems if possible.

scholarly journals Stability analysis of three exoplanet systems

2020 ◽  
Vol 494 (2) ◽  
pp. 2280-2288
Author(s):  
J P Marshall ◽  
J Horner ◽  
R A Wittenmyer ◽  
J T Clark ◽  
M W Mengel
Keyword(s):  
Time Scales ◽  
Planetary Systems ◽  
Orbital Parameters ◽  
Exoplanetary Systems ◽  
Best Fitting ◽  
The Stability ◽  
Short Time ◽  
Exoplanet Systems ◽  
Best Fit

ABSTRACT The orbital solutions of published multiplanet systems are not necessarily dynamically stable on time-scales comparable to the lifetime of the system as a whole. For this reason, dynamical tests of the architectures of proposed exoplanetary systems are a critical tool to probe the stability and feasibility of the candidate planetary systems, with the potential to point the way towards refined orbital parameters of those planets. Such studies can even help in the identification of additional companions in such systems. Here, we examine the dynamical stability of three planetary systems, orbiting HD 67087, HD 110014, and HD 133131A. We use the published radial velocity measurements of the target stars to determine the best-fitting orbital solutions for these planetary systems using the systemic console. We then employ the N-body integrator mercury to test the stability of a range of orbital solutions lying within 3σ of the nominal best fit for a duration of 100 Myr. From the results of the N-body integrations, we infer the best-fitting orbital parameters using the Bayesian package astroemperor. We find that both HD 110014 and HD 133131A have long-term stable architectures that lie within the 1σ uncertainties of the nominal best fit to their previously determined orbital solutions. However, the HD 67087 system exhibits a strong tendency towards instability on short time-scales. We compare these results to the predictions made from consideration of the angular momentum deficit criterion, and find that its predictions are consistent with our findings.

scholarly journals 18. Model Atmospheres for Hydrogen-Deficient White Dwarfs

1971 ◽  
Vol 42 ◽  
pp. 125-129
Author(s):  
I. Bues
Keyword(s):  
Effective Temperature ◽  
White Dwarfs ◽  
Atmospheric Parameters ◽  
Metal Abundances ◽  
Different Parts

The determination of atmospheric parameters for non-DA white dwarfs is investigated with the computed helium-rich model atmospheres by Bues (1970). Only poor predictions are possible from UBV colors alone for DB and DC stars. From uvby colors a determination of effective temperature is possible within 1000 K. Profiles of lines in different parts of the spectrum are necessary for better results.A deficiency of metal abundances for the cooler non-DA stars is obtained.

scholarly journals Meteorite evidence for partial differentiation and protracted accretion of planetesimals

2020 ◽  
Vol 6 (30) ◽  
pp. eaba1303
Author(s):  
Clara Maurel ◽  
James F. J. Bryson ◽  
Richard J. Lyons ◽  
Matthew R. Ball ◽  
Rajesh V. Chopdekar ◽  
...  
Keyword(s):  
Parent Body ◽  
Thermal Impact ◽  
Iron Meteorites ◽  
Planetary Body ◽  
Classification Schemes ◽  
Partial Differentiation ◽  
Internal Structures ◽  
Natural Outcome ◽  
Collisional Evolution

Modern meteorite classification schemes assume that no single planetary body could be source of both unmelted (chondritic) and melted (achondritic) meteorites. This dichotomy is a natural outcome of formation models assuming that planetesimal accretion occurred nearly instantaneously. However, it has recently been proposed that the accretion of many planetesimals lasted over ≳1 million years (Ma). This could have resulted in partially differentiated internal structures, with individual bodies containing iron cores, achondritic silicate mantles, and chondritic crusts. This proposal can be tested by searching for a meteorite group containing evidence for these three layers. We combine synchrotron paleomagnetic analyses with thermal, impact, and collisional evolution models to show that the parent body of the enigmatic IIE iron meteorites was such a partially differentiated planetesimal. This implies that some chondrites and achondrites simultaneously coexisted on the same planetesimal, indicating that accretion was protracted and that apparently undifferentiated asteroids may contain melted interiors.

Sign in / Sign up

Export Citation Format

Share Document