scholarly journals The New Generation Planetary Population Synthesis (NGPPS). IV. Planetary systems around low-mass stars

2021 ◽  
Author(s):  
R. Burn ◽  
M. Schlecker ◽  
C. Mordasini ◽  
A. Emsenhuber ◽  
Y. Alibert ◽  
...  
Keyword(s):  
Planetary Systems ◽  
Population Synthesis ◽  
Low Mass Stars ◽  
Low Mass ◽  
New Generation

scholarly journals Diverse outcomes of planet formation and composition around low-mass stars and brown dwarfs

2019 ◽  
Author(s):  
Y Miguel ◽  
A Cridland ◽  
C W Ormel ◽  
J J Fortney ◽  
S Ida
Keyword(s):  
Planet Formation ◽  
Planetary Systems ◽  
Brown Dwarfs ◽  
Population Synthesis ◽  
Optimal Conditions ◽  
Low Mass Stars ◽  
Water Fraction ◽  
Low Mass ◽  
M Stars ◽  
Mass Form

Abstract The detection of Earth-size exoplanets around low-mass stars –in stars such as Proxima Centauri and TRAPPIST-1– provide an exceptional chance to improve our understanding of the formation of planets around M stars and brown dwarfs. We explore the formation of such planets with a population synthesis code based on a planetesimal-driven model previously used to study the formation of the Jovian satellites. Because the discs have low mass and the stars are cool, the formation is an inefficient process that happens at short periods, generating compact planetary systems. Planets can be trapped in resonances and we follow the evolution of the planets after the gas has dissipated and they undergo orbit crossings and possible mergers. We find that formation of planets above Mars mass and in the planetesimal accretion scenario, is only possible around stars with masses M⋆ ≥ 0.07Msun and discs of Mdisc ≥ 10−2 Msun. We find that planets above Earth-mass form around stars with masses larger than 0.15 Msun, while planets larger than 5 M⊕ do not form in our model, even not under the most optimal conditions (massive disc), showing that planets such as GJ 3512b form with another, more efficient mechanism. Our results show that the majority of planets form with a significant water fraction; that most of our synthetic planetary systems have 1, 2 or 3 planets, but planets with 4,5,6 and 7 planets are also common, confirming that compact planetary systems with many planets should be a relatively common outcome of planet formation around small stars.

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 Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. IV. Updated Properties for 86 Cool Dwarfs Observed during Campaigns 1–17

2019 ◽  
Vol 158 (2) ◽  
pp. 87 ◽  
Author(s):  
Courtney D. Dressing ◽  
Kevin Hardegree-Ullman ◽  
Joshua E. Schlieder ◽  
Elisabeth R. Newton ◽  
Andrew Vanderburg ◽  
...  
Keyword(s):  
Planetary Systems ◽  
Low Mass Stars ◽  
Low Mass ◽  
Cool Dwarfs

scholarly journals Large-scale magnetic fields of low-mass dwarfs: the many faces of dynamo

2010 ◽  
Vol 6 (S271) ◽  
pp. 23-31 ◽  
Author(s):  
J.-F. Donati
Keyword(s):  
Spectral Type ◽  
Large Scale ◽  
Theoretical Modelling ◽  
Dynamo Action ◽  
Low Mass Stars ◽  
Large Scale Field ◽  
Low Mass ◽  
The Many ◽  
New Generation ◽  
Cool Dwarfs

AbstractMagnetic field are ubiquitous to low-mass stars and can potentially impact their evolution and their internal structure; yet the physical processes (called dynamo) that succeed at generating them in the stellar convective zones of cool dwarfs are still enigmatic. Although theoretical modelling and numerical simulations of stellar dynamo action showed breathtaking progress in the last decade, they are not yet in the state of accurately predicting the various magnetic topologies that different low-mass stars can generate.Thanks to the advent of new-generation instruments, spectropolarimetric observations can now reveal the large-scale magnetic topologies of cool dwarfs, from the brown dwarf threshold (spectral type M8) up to the limit beyond which outer convective zones get vanishingly small (spectral type F5). In particular, they can reconstruct through tomographic methods the poloidal and toroidal components of the large-scale field, hence offering a fresh option for guiding dynamo theories to a more mature state.We review here the latest observational advances, showing in particular that magnetic topologies of low-mass dwarfs can drastically vary with mass and rotation rate, and discuss their implications for our understanding of dynamo processes.

scholarly journals The K2-HERMES Survey: age and metallicity of the thick disc

2019 ◽  
Vol 490 (4) ◽  
pp. 5335-5352 ◽  
Author(s):  
Sanjib Sharma ◽  
Dennis Stello ◽  
Joss Bland-Hawthorn ◽  
Michael R Hayden ◽  
Joel C Zinn ◽  
...  
Keyword(s):  
Selection Function ◽  
Population Synthesis ◽  
Low Mass Stars ◽  
Mass Scaling ◽  
Elemental Abundances ◽  
Thick Disc ◽  
Promising Tool ◽  
Low Mass ◽  
The Mean ◽  
First Time

ABSTRACT Asteroseismology is a promising tool to study Galactic structure and evolution because it can probe the ages of stars. Earlier attempts comparing seismic data from the Kepler satellite with predictions from Galaxy models found that the models predicted more low-mass stars compared to the observed distribution of masses. It was unclear if the mismatch was due to inaccuracies in the Galactic models, or the unknown aspects of the selection function of the stars. Using new data from the K2 mission, which has a well-defined selection function, we find that an old metal-poor thick disc, as used in previous Galactic models, is incompatible with the asteroseismic information. We use an importance-sampling framework, which takes the selection function into account, to fit for the metallicities of a population synthesis model using spectroscopic data. We show that spectroscopic measurements of [Fe/H] and [α/Fe] elemental abundances from the GALAH survey indicate a mean metallicity of log (Z/Z⊙) = −0.16 for the thick disc. Here Z is the effective solar-scaled metallicity, which is a function of [Fe/H] and [α/Fe]. With the revised disc metallicities, for the first time, the theoretically predicted distribution of seismic masses show excellent agreement with the observed distribution of masses. This indirectly verifies that the asteroseismic mass scaling relation is good to within five per cent. Assuming the asteroseismic scaling relations are correct, we estimate the mean age of the thick disc to be about 10 Gyr, in agreement with the traditional idea of an old α-enhanced thick disc.

scholarly journals Accretion Disks around low-mass Stars unveiled by the new Generation of cm to submm Arrays

2009 ◽  
Vol 5 (H15) ◽  
pp. 239-240
Author(s):  
Anne Dutrey
Keyword(s):  
Accretion Disks ◽  
Planet Formation ◽  
Angular Resolution ◽  
Frequency Range ◽  
Low Mass Stars ◽  
Low Mass ◽  
Dust Disks ◽  
New Generation ◽  
The Impact

AbstractIn the context of accretion disks, I briefly discuss the impact of three major forthcoming radio facilities: e-VLA, ALMA and SKA. These arrays are complementary by their frequency range and angular resolution. Around nearby low-mass stars, they will likely provide the first insights in the inner gas and dust disks (radius < 10-30 AU) in the area where planet formation should occur but would also allow the first investigations of the star, jet and disk connections.

scholarly journals Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. III. A High Mass and Low Envelope Fraction for the Warm Neptune K2-55b

2018 ◽  
Vol 156 (2) ◽  
pp. 70 ◽  
Author(s):  
Courtney D. Dressing ◽  
Evan Sinukoff ◽  
Benjamin J. Fulton ◽  
Eric D. Lopez ◽  
Charles A. Beichman ◽  
...  
Keyword(s):  
Planetary Systems ◽  
High Mass ◽  
Low Mass Stars ◽  
Low Mass

scholarly journals Characterizing K2 Candidate Planetary Systems Orbiting Low-mass Stars. I. Classifying Low-mass Host Stars Observed during Campaigns 1–7

2017 ◽  
Vol 836 (2) ◽  
pp. 167 ◽  
Author(s):  
Courtney D. Dressing ◽  
Elisabeth R. Newton ◽  
Joshua E. Schlieder ◽  
David Charbonneau ◽  
Heather A. Knutson ◽  
...  
Keyword(s):  
Planetary Systems ◽  
Low Mass Stars ◽  
Low Mass ◽  
Host Stars

scholarly journals PLANETS AROUND LOW-MASS STARS (PALMS). IV. THE OUTER ARCHITECTURE OF M DWARF PLANETARY SYSTEMS

2014 ◽  
Vol 216 (1) ◽  
pp. 7 ◽  
Author(s):  
Brendan P. Bowler ◽  
Michael C. Liu ◽  
Evgenya L. Shkolnik ◽  
Motohide Tamura
Keyword(s):  
Planetary Systems ◽  
Low Mass Stars ◽  
Low Mass ◽  
M Dwarf

scholarly journals Pebbles versus planetesimals: the case of Trappist-1

2019 ◽  
Vol 631 ◽  
pp. A7 ◽  
Author(s):  
G. A. L. Coleman ◽  
A. Leleu ◽  
Y. Alibert ◽  
W. Benz
Keyword(s):  
Water Content ◽  
Initial Conditions ◽  
Planetary Systems ◽  
Central Star ◽  
Low Mass Stars ◽  
Formation Pathway ◽  
Wide Range ◽  
Mass Size ◽  
Low Mass ◽  
Inner Region

We present a study into the formation of planetary systems around low mass stars similar to Trappist-1, through the accretion of either planetesimals or pebbles. The aim is to determine if the currently observed systems around low mass stars could favour one scenario over the other. To determine these differences, we ran numerous N-body simulations, coupled to a thermally evolving viscous 1D disc model, and including prescriptions for planet migration, photoevaporation, and pebble and planetesimal dynamics. We mainly examine the differences between the pebble and planetesimal accretion scenarios, but we also look at the influences of disc mass, size of planetesimals, and the percentage of solids locked up within pebbles. When comparing the resulting planetary systems to Trappist-1, we find that a wide range of initial conditions for both the pebble and planetesimal accretion scenarios can form planetary systems similar to Trappist-1, in terms of planet mass, periods, and resonant configurations. Typically these planets formed exterior to the water iceline and migrated in resonant convoys into the inner region close to the central star. When comparing the planetary systems formed through pebble accretion to those formed through planetesimal accretion, we find a large number of similarities, including average planet masses, eccentricities, inclinations, and period ratios. One major difference between the two scenarios was that of the water content of the planets. When including the effects of ablation and full recycling of the planets’ envelope with the disc, the planets formed through pebble accretion were extremely dry, whilst those formed through planetesimal accretion were extremely wet. If the water content is not fully recycled and instead falls to the planets’ core, or if ablation of the water is neglected, then the planets formed through pebble accretion are extremely wet, similar to those formed through planetesimal accretion. Should the water content of the Trappist-1 planets be determined accurately, this could point to a preferred formation pathway for planetary systems, or to specific physics that may be at play.

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