CAN NEUTRON-STARS ABLATE THEIR COMPANIONS

Ablation of stars by energetic photons from a compact companion is considered for general parameters. It is concluded that pulsars with conventional parameters cannot ablate their companions with gamma rays at orbital separation of 3 x 10(10) cm or more. It is estimated that in the absence of heat conductivity, line cooling is important when the incident radiation flux is less than 10(15) ergs s-1 cm-2. It is proposed that millisecond pulsars may be able to ablate their companions more readily than in previous scenarios if even a small fraction of the kilohertz radiation is absorbed by the atmosphere/wind of the companion and the heat conducted to the surface. It is noted that there are several scenarios in which low-mass companions can evolve from m > 0.1 M. to m < 0.05 M. provided the companion nearly fills its Roche lobe. If contact with the Roche lobe is not constantly maintained by angular momentum loss, and if self-sustained accretion cannot occur without this contact, then the lack of fading LMXBs can be attributed to accretion nulling, punctuated by periods of vigorous accretion.