The turn-on of mass transfer in AM CVn binaries: Implications for RX J0806 +1527 and RX J1914+2456

Christopher J. Deloye*, Ronald E. Taam

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

15 Scopus citations


We report on evolutionary calculations of the onset of mass transfer in AM CVn binaries, treating the donor's evolution in detail. We show that during the early contact phase, while the mass transfer rate, Ṁ, is increasing, gravity wave emission continues to drive the binary to shorter orbital period, Porb. We argue that the phase where M > 0 and v̇ > 0 (v = 1//Jorb) can last between 103 and 106 yr, significantly longer than previously estimated. These results are applied to RX J0806+1527 (Porb = 321 s) and RX J914+2456 (Porb = 569 s), both of which have measured v̇ > 0. Thus, a v̇ > 0 does not select between the unipolar inductor and accretion-driven models proposed as the source of X-rays in these systems. For the accretion model, we predict for RX J0806 that v̈ ≈ (1.0-1.5) × 10-28 Hz s-2 and argue that timing observations can probe v̈ at this level with a total ≈20 yr baseline. We also place constraints on each system's initial parameters given current observational data.

Original languageEnglish (US)
Pages (from-to)L99-L102
JournalAstrophysical Journal
Issue number2 II
StatePublished - Oct 1 2006


  • Binaries: close
  • Gravitational waves
  • White dwarfs

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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