Mass-loss through the L2 Lagrange point - Application to main-sequence EMRI

Itai Linial*, Re'Em Sari

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

30 Scopus citations


We consider stable mass transfer from the secondary to the primary of an extreme mass ratio binary system. We show that when the mass transfer is sufficiently fast, mass leakage occurs through the outer Lagrange point L2, in addition to the usual transfer through L1. We provide an analytical estimate for the mass leakage rate through L2 and find the conditions in which it is comparable to the mass transfer rate through L1. Focusing on a binary system of a mainsequence star and a supermassive black hole, driven by the emission of gravitational radiation, we show that it may sustain stable mass transfer, along with mass-loss through L2. If such a mass transferring system occurs at our Galactic Centre, it produces a gravitational wave signal detectable by future detectors, such as Laser Interferometer Space Antenna (LISA). The signal evolves according to the star's adiabatic index and cooling time. For low-mass stars, the evolution is faster than the Kelvin-Helmholtz cooling rate driving the star out of the main-sequence. In some cases, the frequency and amplitude of the signal may both decrease with time, contrary to the standard chirp of a coalescing binary. Mass-loss through L2, when occurs, decreases the evolution time-scale of the emitted gravitational wave signal by up to a few tens of per cent. We conclude that L2 mass ejection is a crucial factor in analysing gravitational waves signals produced by such systems.

Original languageAmerican English
Pages (from-to)2441-2454
Number of pages14
JournalMonthly Notices of the Royal Astronomical Society
Issue number2
StatePublished - 1 Aug 2017

Bibliographical note

Publisher Copyright:
© 2017 Oxford University Press. All rights reserved.


  • Binaries: general
  • Gravitational waves
  • Stars: mass-loss


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