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Where can a Trappist-1 planetary system be produced?

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Title: Where can a Trappist-1 planetary system be produced?
Authors: Haworth, TJ
Facchini, S
Clarke, CJ
Mohanty, S
Item Type: Journal Article
Abstract: We study the evolution of protoplanetary discs that would have been precursors of a Trappist-1-like system under the action of accretion and external photoevaporation in different radiation environments. Dust grains swiftly grow above the critical size below which they are entrained in the photoevaporative wind, so although gas is continually depleted, dust is resilient to photoevaporation after only a short time. This means that the ratio of the mass in solids (dust plus planetary) to the mass in gas rises steadily over time. Dust is still stripped early on, and the initial disc mass required to produce the observed 4 M⊕ of Trappist-1 planets is high. For example, assuming a Fatuzzo & Adams distribution of UV fields, typical initial disc masses have to be >30 per cent the stellar (which are still Toomre Q stable) for the majority of similar mass M dwarfs to be viable hosts of the Trappist-1 planets. Even in the case of the lowest UV environments observed, there is a strong loss of dust due to photoevaporation at early times from the weakly bound outer regions of the disc. This minimum level of dust loss is a factor of 2 higher than that which would be lost by accretion on to the star during 10 Myr of evolution. Consequently, even in these least irradiated environments, discs that are viable Trappist-1 precursors need to be initially massive (>10 per cent of the stellar mass).
Issue Date: 20-Jan-2018
Date of Acceptance: 17-Jan-2018
URI: http://hdl.handle.net/10044/1/58779
DOI: https://dx.doi.org/10.1093/mnras/sty168
ISSN: 0035-8711
Publisher: Oxford University Press (OUP)
Start Page: 5460
End Page: 5473
Journal / Book Title: Monthly Notices of the Royal Astronomical Society
Volume: 475
Issue: 4
Copyright Statement: This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society © 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Keywords: Science & Technology
Physical Sciences
Astronomy & Astrophysics
accretion
accretion discs
hydrodynamics
protoplanetary discs
circumstellar matter
photodissociation region (PDR)
SPITZER-SPACE-TELESCOPE
EMBEDDED STAR-CLUSTERS
T-TAURI STARS
PHOTODISSOCIATION REGIONS
PROTOPLANETARY DISCS
TERRESTRIAL PLANETS
CIRCUMSTELLAR DISKS
ORIONIS CLUSTER
STELLAR GROUPS
RADIATION
0201 Astronomical And Space Sciences
Publication Status: Published
Open Access location: https://arxiv.org/pdf/1801.05822.pdf
Appears in Collections:Physics
Astrophysics