Supernova kicks, magnetic braking, and neutron star binaries

V. Kalogera*, U. Kolb, A. R. King

*Corresponding author for this work

Research output: Contribution to journalArticle

22 Scopus citations

Abstract

We consider the formation of low-mass X-ray binaries (LMXBs) containing accreting neutron stars via the helium star supernova channel. The predicted relative number of short-period transients provides a sensitive test of the input physics in this process. We investigate the effect of varying mean kick velocities, orbital angular momentum loss efficiencies, and common-envelope ejection efficiencies on the subpopulation of short-period systems, both transient and persistent. Guided by the thermal-viscous disk instability model in irradiation-dominated disks, we posit that short-period transients have donors close to the end of core hydrogen burning. We find that with increasing mean kick velocity the overall short-period fraction, s, grows, while the fraction r of systems with evolved donors among short-period systems drops. This effect, acting in opposite directions on these two fractions, allows us to constrain models of LMXB formation through comparison with observational estimates of s and r. Without fine tuning or extreme assumptions about evolutionary parameters, consistency between models and current observations is achieved for a regime of intermediate average kick magnitudes of about 100-200 km s-1, provided that (1) orbital braking for systems with donor masses in the range 1-1.5 M is weak, i.e., much less effective than a simple extrapolation of standard magnetic braking beyond 1.0 M would suggest, and (2) the efficiency of common-envelope ejection is low.

Original languageEnglish (US)
Pages (from-to)967-977
Number of pages11
JournalAstrophysical Journal
Volume504
Issue number2 PART I
DOIs
StatePublished - 1998

Keywords

  • Accretion, accretion disks
  • Binaries: close
  • Stars: evolution
  • Stars: neutron
  • Supernovae: general
  • X-rays: stars

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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