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Abstract Observations suggest that the hot Neptune desert contains the remnants of destroyed gas giants. Recent theoretical work has shown that gas giant destruction via Roche lobe overflow (RLO) can indeed populate the desert with remnant planets, but only if mass transfer removes most of the planet’s orbital angular momentum (“lossy” RLO). Motivated by the fact that stellar accretion naturally gives rise to such lossy RLO, in this Letter we examine how planet-to-star mass and angular momentum transfer manifests in the distribution of stellar obliquities. We find that RLO tilts host stars into spin–orbit alignment (within a few ∼tens of degrees) regardless of initial conditions. Obliquity damping by RLO can only be reversed by the presence of misaligned companion planets within ≲2 au. While tides and mass transfer usually produce stellar spin-up, host stars can also emerge from RLO slowly rotating if systems begin strongly retrograde; retrograde RLO reconciles theory with the anomalously slow rotation of the desert-dweller host, LTT 9779. Predicted spin–orbit alignment may differentiate RLO from alternative giant planet destruction mechanisms, in particular hot Jupiter disruption during high-eccentricity migration (which tends to produce broadly distributed stellar obliquities). We summarize other population-level predictions that can further distinguish RLO from high-eccentricity migration. Our work suggests that follow-up obliquity measurements may reveal the formation pathways of desert dwellers and potentially open a window into gas giants’ exposed interiors.
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This content will become publicly available on April 30, 2027
Stability of Multiplanet Systems through Hot Jupiter Destruction
Abstract Recent observational and theoretical work suggests that the sub-Jovian desert (periods ≲3 days, masses ∼10–100M⊕) hosts the remains of destroyed hot Jupiters (“desert dwellers”). In this work, we explore how differing hot Jupiter destruction mechanisms—Roche lobe overflow (RLO) versus tidal disruption during high-eccentricity migration (HEM)—may be discerned observationally based on the presence of companion planets to desert dwellers. We show that gas giant destruction via RLO clears out the desert of any companions inside orbital periods ≲4 days; desert dwellers should sit alone in the desert if they form through this mechanism. Numerically mapping the instability threshold in planet mass and orbital distance, we find that the majority of observed companions to desert dwellers are safely in the stability region. RLO therefore does not preclude the existence of nearby companions beyond the desert, in contrast to gas giant tidal disruption during HEM. Further characterization of desert dweller systems may therefore elucidate the fates of hot Jupiters.
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- Award ID(s):
- 2306391
- PAR ID:
- 10702345
- Publisher / Repository:
- IOP Publishing
- Date Published:
- Journal Name:
- The Astrophysical Journal Letters
- Volume:
- 1002
- Issue:
- 1
- ISSN:
- 2041-8205
- Page Range / eLocation ID:
- L30
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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