Eccentric millisecond pulsars by resonant convection

Sivan Ginzburg*, Eugene Chiang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Eccentric millisecond pulsars (eMSPs) with white dwarf companions exhibit orbital eccentricities orders of magnitude larger than predicted by turbulent convection in the white dwarfs' red giant progenitors. The orbital periods of eMSPs cluster around P = 20-30 d, remarkably close to the red giant convective eddy turnover time teddy. We propose that the anomalously large eccentricities are resonantly driven by convective flows somehow made coherent when the turnover time matches the tidally locked red giant's spin period, which is also the tidal forcing period. Numerical simulations of rotating red giants and magnetic field studies of stars show some evidence for especially ordered flow patterns when the convective Rossby number P/teddy is of order unity. We show that resonant convection boosts eccentricities by a factor of (tnuc/P)1/2 ≈ 3 × 103 over the random-walk values that characterize conventional MSPs, in good agreement with observations (tnuc is the giant's nuclear burning time-scale). We also show how variations in the eddy turnover time arising from red giant metallicity variations can reproduce the observed effective width of the resonance, ΔP/P ≈ 0.4.

Original languageAmerican English
Pages (from-to)L1-L5
JournalMonthly Notices of the Royal Astronomical Society: Letters
Volume509
Issue number1
DOIs
StatePublished - 1 Jan 2022
Externally publishedYes

Bibliographical note

Publisher Copyright:
© 2022 2021 The Author(s) Published by Oxford University Press on behalf of Royal Astronomical Society.

Keywords

  • binaries: general
  • convection
  • pulsars: general
  • white dwarfs

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