The evolution of low mass, close binary systems with a neutron star component: a detailed grid

M. A. DE VITO, O. G. BENVENUTO

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Oxford; Año: 2012 vol. 421 p. 2206 - 2222

0035-8711

In  close binary  systems  composed of  a  normal, donor  star and  anaccreting  neutron  star,  the  amount  of material  received  by  theaccreting component  is, so  far, a real  intrigue. In  the literaturethere are  available models that  link the accretion  disk surroundingthe neutron star with the amount of material it receives, but there isno model linking  the amount of matter lost by the  donor star to thatfalling onto the neutron star.In  this paper  we explore  the evolutionary  response of  these closebinary systems  when we  vary the amount  of material accreted  by the neutron star.  We consider a parameter beta which  represents the fraction of material  lost by the normal star that  can be accreted by the  neutron  star. Beta  is considered  as  constant  throughoutevolution.   We  have  computed  the  evolution of  a  set  of  modelsconsidering initial  donor star  masses M_i/ msun between  0.5 and3.50,  initial  orbital periods  P_i/days  between  0.175 and  12,initial  masses of  neutron  stars (M_{NS})_i / msun of  0.80,1.00, 1.20 and  1.40 and several values of  beta. We assumed solarabundances.  These  systems evolve to  ultracompact or to  open binary systems, many of which form  low mass helium white dwarfs.  We present a grid of calculations and analyze how these results are affected upon changes in  the value of beta. We find a  weak dependence  of the final donor star  mass with respect to beta. In  most cases this is also true for the final orbital period. The most sensitive quantity is the final mass of the accreting neutron star.As we  do not know the initial  mass and rotation rate  of the neutronstar of  any system, we  find that performing evolutionary  studies isnot helpful for determining beta.