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Title: Formation of Close-in Neptunes around Low-mass Stars through Breaking Resonant Chains
Abstract Conventional planet formation theories predict a paucity of massive planets around small stars, especially very low-mass (0.1−0.3M⊙) mid-to-late M dwarfs. Such tiny stars are expected to form planets of terrestrial sizes but not much bigger. However, this expectation is challenged by the recent discovery of LHS 3154 b, a planet with period of 3.7 days and minimum mass of 13.2M⊕orbiting a 0.11M⊙star. Here, we propose that close-in Neptune-mass planets like LHS 3154 b formed through an anomalous series of mergers from a primordial compact system of super-Earths. We perform simulations within the context of the “breaking the chains” scenario, in which super-Earths initially form in tightly spaced chains of mean-motion resonances before experiencing dynamical instabilities and collisions. Planets as massive and close-in as LHS 3154 b (Mp∼ 12−20M⊕,P< 7 days) are produced in ∼1% of simulated systems, in broad agreement with their low observed occurrence. These results suggest that such planets do not require particularly unusual formation conditions but rather are an occasional by-product of a process that is already theorized to explain compact multiplanet systems. Interestingly, our simulated systems with LHS 3154 b-like planets also contain smaller planets at around ∼30 days, offering a possible test of this hypothesis.  more » « less
Award ID(s):
2306391
PAR ID:
10548744
Author(s) / Creator(s):
;
Publisher / Repository:
DOI PREFIX: 10.3847
Date Published:
Journal Name:
The Astrophysical Journal
Volume:
974
Issue:
2
ISSN:
0004-637X
Format(s):
Medium: X Size: Article No. 207
Size(s):
Article No. 207
Sponsoring Org:
National Science Foundation
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