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arxiv: 2604.19918 · v2 · submitted 2026-04-21 · 🌌 astro-ph.EP

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Stability of Multiplanet Systems Through Hot Jupiter Destruction

Donald Liveoak , Tim Hallatt , Sarah Millholland
Authors on Pith no claims yet

Pith reviewed 2026-05-10 00:50 UTC · model grok-4.3

classification 🌌 astro-ph.EP
keywords sub-Jovian deserthot JupitersRoche lobe overflowhigh-eccentricity migrationplanetary stabilityexoplanet companionsdesert dwellers
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The pith

Roche lobe overflow destruction of hot Jupiters clears all companions inside orbital periods of about 4 days.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper examines how the way hot Jupiters are destroyed can be tested by looking for companion planets around the surviving sub-Jovian planets that remain in the desert. If destruction occurs through Roche lobe overflow, the process removes any nearby companions with periods shorter than roughly 4 days, so desert dwellers should orbit alone. A reader would care because this offers a direct observational signature to separate different destruction pathways and understand the final stages of close-in giant planet evolution. The authors calculate stability thresholds across planet masses and distances to show that most known companions to desert dwellers sit safely outside the cleared zone. This stands in contrast to high-eccentricity migration followed by tidal disruption, which would remove companions differently.

Core claim

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, 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.

What carries the argument

Numerical mapping of the dynamical instability threshold in planet mass and orbital distance for systems that include a desert dweller after gas giant destruction.

If this is right

  • Desert dwellers formed by RLO should have no companions inside periods of about 4 days.
  • The majority of currently observed companions to desert dwellers occupy stable orbits.
  • RLO destruction permits companions outside the desert, unlike tidal disruption during HEM.
  • Detailed follow-up observations of desert dweller systems can distinguish between hot Jupiter destruction channels.

Where Pith is reading between the lines

These are editorial extensions of the paper, not claims the author makes directly.

  • Stability calculations provide a practical filter for selecting targets in searches for additional planets around desert dwellers.
  • Systems that show close companions inside the limit would favor HEM or other mechanisms over RLO.
  • The result links the architecture of multiplanet systems to the specific pathway that removes their original gas giants.

Load-bearing premise

The numerical mapping of the instability threshold in planet mass and orbital distance accurately captures real-system dynamics without additional effects such as ongoing migration or tides.

What would settle it

Detection of even one companion planet with orbital period shorter than 4 days around a confirmed desert dweller would show that the RLO clearing process does not operate as mapped.

Figures

Figures reproduced from arXiv: 2604.19918 by Donald Liveoak, Sarah Millholland, Tim Hallatt.

Figure 1
Figure 1. Figure 1: Hot Jupiter Roche lobe overflow evolution tracks, as computed by Hallatt & Millholland (2026) (black data) and our implementation in REBOUND (colored data points). Blue, orange, and green data points correspond to hot Jupiters containing 10, 20, and 30 M⊕ cores respectively, which end mass transfer at differing periods and masses (for our choice of initial planet entropy 8 kB/mH where kB is Boltzmann’s con… view at source ↗
Figure 2
Figure 2. Figure 2: Two example systems (top and bottom panels) comprising an outer gas giant companion (orange curves) to an inner hot Jupiter which undergoes RLO en route to becoming a desert dweller (blue curves). Left panels depict planet mass evolution, middle planet semi-major axis evolution, while right show the mutual inclination between the two planets. Top panels place the outer companion at 0.2 au; the system is on… view at source ↗
Figure 3
Figure 3. Figure 3: Heatmap recording proportion of synthetic systems that are unstable after the inner hot Jupiter undergoes RLO. Each system consists of an outer companion of varying periapse distance (rp, y axis) and mass (x axis), with an inner hot Jupiter that undergoes RLO. Panels use a hot Jupiter of core mass Mcore=10, 20, 30 M⊕ from left to right, respectively. Orange markers indicate the parameters of several observ… view at source ↗
Figure 4
Figure 4. Figure 4: A representative example of orbital instability caused by RLO, with Mcore = 10M⊕. Top to bottom panels: resonant argument associated with the 2:1 commensurabil￾ity, eccentricity of desert dweller (orange) and companion (green), and planet/planet orbital separation normalized by the mean (∆a/a¯=2(a2−a1)/(a2 + a1)) for the planet pair (orange) and the threshold for Hill stability ((∆a/a¯)crit, in green; foll… view at source ↗
Figure 5
Figure 5. Figure 5 [PITH_FULL_IMAGE:figures/full_fig_p008_5.png] view at source ↗
read the original abstract

Recent observational and theoretical work suggests that the sub-Jovian desert (periods ${\lesssim}3$ days, masses ${\sim}10{-}100 \ M_{\oplus}$) hosts the remains of destroyed hot Jupiters (``desert dwellers"). In this work, we explore how differing hot Jupiter destruction mechanisms -- Roche lobe overflow (RLO) vs. 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 ${\lesssim}$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.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

1 major / 0 minor

Summary. The manuscript claims that hot Jupiter destruction via Roche lobe overflow (RLO) clears the sub-Jovian desert of any companion planets with orbital periods ≲4 days, so that desert dwellers formed through this channel should appear isolated within the desert. In contrast, tidal disruption during high-eccentricity migration (HEM) does not impose this isolation. The authors support the claim by numerically mapping the gravitational instability threshold in planet mass and orbital distance via N-body integrations, finding that the majority of observed companions to desert dwellers lie safely outside the unstable region.

Significance. If the central result holds, the work supplies a concrete observational discriminant between RLO and HEM destruction channels that could help explain both the sub-Jovian desert and the apparent isolation of some desert dwellers. The use of independent numerical integrations to locate the stability boundary, rather than fitting to the observational signature itself, is a methodological strength that avoids circularity.

major comments (1)
  1. The numerical mapping of the instability threshold (described in the abstract and the methods section on N-body integrations) is performed under the assumption of isolated gravitational dynamics. The paper should quantify how the ≲4-day boundary shifts when tidal dissipation or disk-driven migration terms are added, because these processes can operate on comparable timescales and could either permit companions inside the quoted cutoff or destabilize systems currently classified as stable. A minimal test would be to rerun a representative subset of the integrations with standard tidal prescriptions included.

Simulated Author's Rebuttal

1 responses · 0 unresolved

We thank the referee for their positive assessment of the manuscript and for identifying a useful avenue to strengthen the numerical results. We address the major comment below and will revise the paper to incorporate the suggested test.

read point-by-point responses

  1. Referee: The numerical mapping of the instability threshold (described in the abstract and the methods section on N-body integrations) is performed under the assumption of isolated gravitational dynamics. The paper should quantify how the ≲4-day boundary shifts when tidal dissipation or disk-driven migration terms are added, because these processes can operate on comparable timescales and could either permit companions inside the quoted cutoff or destabilize systems currently classified as stable. A minimal test would be to rerun a representative subset of the integrations with standard tidal prescriptions included.

    Authors: We agree that the current N-body integrations consider only gravitational dynamics. Our central claim concerns the gravitational clearing of companions during RLO-driven destruction, which occurs on timescales where close encounters dominate. Disk-driven migration is not expected to operate after disk dispersal, but tidal dissipation could in principle alter eccentricities and thus the instability threshold. To quantify any shift, we will rerun a representative subset of the integrations (covering companion masses 1-20 M⊕ and periods 1-6 days) with standard tidal prescriptions included, using a constant time-lag model with Q values typical for gas giants and rocky planets. The revised manuscript will report the updated boundary and any changes to the classification of observed companions. revision: yes

Circularity Check

0 steps flagged

No circularity: stability thresholds obtained via independent N-body integrations

full rationale

The paper derives its central claim—that RLO destruction clears companions inside ≲4 days—by numerically mapping the instability threshold in planet mass and orbital distance through direct N-body integrations. These thresholds are computed from first-principles gravitational dynamics under stated assumptions and are not defined in terms of the target observational signature, fitted to desert-dweller data, or reduced to self-citations. No self-definitional steps, fitted-input predictions, or load-bearing self-citation chains appear in the derivation chain. The mapping is externally falsifiable via independent simulations and does not rename known results or smuggle ansatzes. This is the most common honest non-finding for papers whose core result rests on numerical experiment rather than algebraic closure.

Axiom & Free-Parameter Ledger

1 free parameters · 2 axioms · 0 invented entities

The central claim rests on standard assumptions of N-body gravitational dynamics plus the premise that RLO and HEM are the dominant destruction channels; the 4-day threshold emerges from numerical exploration rather than an analytic derivation.

free parameters (1)
  • instability threshold boundary
    Determined numerically from planet mass and orbital distance mapping; no explicit fitted value given in abstract.
axioms (2)
  • domain assumption RLO and HEM are the two primary hot Jupiter destruction mechanisms under consideration
    Invoked in the abstract to frame the observational test.
  • standard math Standard Newtonian N-body dynamics govern long-term stability of multiplanet systems
    Underlying the numerical mapping of instability thresholds.

pith-pipeline@v0.9.0 · 5485 in / 1363 out tokens · 40999 ms · 2026-05-10T00:50:09.065689+00:00 · methodology

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