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Session 16 - Radio Pulsars.
Display session, Monday, January 15
North Banquet Hall, Convention Center
We model the structure and evolution of the secondary of the Black Widow pulsar. The secondary is being ablated by the pulsar, and the system shows orbital period variations of varying sign. Applegate and Shaham (1994) showed that such period changes can be produced by a variable gravitational quadrupole moment in the secondary star. They hypothesized that the energy needed for such changes was derived from the tidal energy deposited in the secondary.
The evolution of the secondary is driven not by chemical evolution as happens in main-sequence stars, nor by gravitational contraction which controls the evolution of brown dwarfs, but by the mass loss caused by interaction with the pulsar. Tidal energy becomes the dominant source of energy for the secondary as the star loses mass and moves below the hydrogen burning minimum mass. This tidal energy deposition changes the structure of the star with respect to a normal star supported by either nuclear burning or gravitational contraction. We present models of the structure of such a star, and a possible evolutionary track for the secondary of the Black Widow pulsar.
