Hot-Jupiter core mass from Roche lobe overflow

Sivan Ginzburg*, Re'em Sari

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

14 Scopus citations


The orbits of many observed hot Jupiters are decaying rapidly due to tidal interaction, eventually reaching the Roche limit.We analytically study the ensuing coupled mass-loss and orbital evolution during the Roche lobe overflow and find two possible scenarios. Planets with light cores Mc ≲ 6M⊕ (assuming a nominal tidal dissipation factor Q ∼ 106 for the host star) are transformed into Neptune-mass gas planets, orbiting at a separation (relative to the stellar radius) a/R∗≈3.5. Planets with heavier coresMc ≳6M⊕ plunge rapidly until they are destroyed at the stellar surface. Remnant gas Neptunes, which are stable to photoevaporation, are absent from the observations despite their unique transit radius (5-10 R⊕). This result suggests that Mc ≳ 6M⊕, providing a useful constraint on the poorly known core mass that may distinguish between different formation theories of gas giants. Alternatively, if one assumes a prior of Mc ≈ 6M⊕ from the core-accretion theory, our results suggest that Q does not lie in the range 106 ≲ Q ≲ 107.

Original languageAmerican English
Pages (from-to)278-285
Number of pages8
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
StatePublished - 1 Jul 2017

Bibliographical note

Publisher Copyright:
© 2017 The Authors.


  • Planet-star interactions
  • Planets and satellites: Composition
  • Planets and satellites: Gaseous planets


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