Aligned Stellar Obliquities for Two Hot Jupiter-hosting M Dwarfs Revealed by MAROON-X: Implications for Hot Jupiter Formation

TL;DR

This study measures the stellar obliquities of two hot Jupiters around M dwarfs, finding they are well-aligned, which supports theories that M dwarf stars efficiently dampen obliquities and that Kozai-Lidov migration may influence their formation.

Contribution

First measurements of the Rossiter-McLaughlin effect for hot Jupiters around M dwarfs, revealing well-aligned systems and providing insights into their formation and migration mechanisms.

Findings

Both systems are well-aligned with small sky-projected obliquities.

The systems are in wide binary configurations, with potential for Kozai-Lidov migration.

M dwarfs likely dampen obliquities more efficiently than AFGK stars.

Abstract

Hot Jupiters (HJs) are $2-3\times$ less common around early M dwarfs than around AFGK stars, suggesting that HJs may form and/or migrate via distinct pathways around different types of stars. One source of insight into HJ formation mechanisms is to trace their dynamical histories through measurements of host stellar obliquities via the Rossiter-McLaughlin (RM) effect. Here we present measurements of the RM effect for the HJs TOI-3714 b and TOI-5293 A b using the Gemini-North/MAROON-X spectrograph. Our measurements represent just the second and third hot Jupiters around M dwarfs (HJMD) with a detection of the RM effect. We find that both systems are well-aligned with sky-projected obliquities of $\lambda = 21^{+14}_{-11}$$\mathrm{^{\circ}}$ and $-12^{+19}_{-14}$$\mathrm{^{\circ}}$ and deprojected obliquities of $\psi = 26^{+11}_{-10}$$\mathrm{^{\circ}}$ and $24^{+11}_{-10}$$\mathrm{^{\circ}}$ for TOI-3714 and TOI-5293 A, respectively. Both stars are in wide binary systems. We refine the stellar parameters by decontaminating their unresolved $K_s$-band photometry and constrain the binary orbits using Gaia DR3 astrometry. We find that the minimum mutual inclination of the planet and binary companion in the TOI-5293 system is sufficiently large to drive Kozai-Lidov (KL) migration while the result for TOI-3714 is inconclusive. We present a population-level analysis of HJs around AFGK versus early M dwarfs and argue that KL migration is more efficient around the latter, which is expected to produce misaligned stellar obliquities in HJMD systems in the absence of efficient tidal damping. The emerging population of well-aligned HJMD hosts supports the expectation that M dwarfs, with their deep convective envelopes, do efficiently dampen misaligned obliquities.