ﻻ يوجد ملخص باللغة العربية
We consider the formation of low-mass X-ray binaries 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, provided that (i) orbital braking for systems with donor masses in the range 1-1.5 solar masses is weak, i.e., much less effective than a simple extrapolation of standard magnetic braking beyond 1.0 solar mass would suggest, and (ii) the efficiency of common envelope ejection is low.
Angular momentum loss in ultracompact binaries, such as the AM Canum Venaticorum stars, is usually assumed to be due entirely to gravitational radiation. Motivated by the outflows observed in ultracompact binaries, we investigate whether magnetically
We present results from a suite of axisymmetric, core-collapse supernova simulations in which hydrodynamic recoil from an asymmetric explosion produces large proto-neutron star (PNS) velocities. We use the adaptive-mesh refinement code CASTRO to self
The idea that gamma-ray bursts might be a kind of phenomena associated with neutron star kicks was first proposed by Dar & Plaga (1999). Here we study this mechanism in more detail and point out that the neutron star should be a high speed one (with
The birth properties of neutron stars yield important information on the still debated physical processes that trigger the explosion and on intrinsic neutron-star physics. These properties include the high space velocities of young neutron stars with
Some fraction of compact binaries that merge within a Hubble time may have formed from two massive stars in isolation. For this isolated-binary formation channel, binaries need to survive two supernova (SN) explosions in addition to surviving common-