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A global model for the origin of pulsar and runaway OB star velocities

Posted on:1994-11-19Degree:Ph.DType:Dissertation
University:Columbia UniversityCandidate:Terman, James LewisFull Text:PDF
GTID:1472390014493740Subject:Physics
Abstract/Summary:
We have developed a model to explore the theory that supernovas in massive binary systems can produce the high velocity populations of runaway OB stars, High Mass X-ray Binaries (HMXB's), Be stars and radio pulsars seen in the Galaxy. Our model takes a Galactic population of OB stars (8-40 M{dollar}sb{lcub}odot{rcub}{dollar}) and evolves them off the main-sequence. In short period binary systems, the primary will fill its Roche lobe and transfer its mass to the secondary as long as the secondary does not overflow its Roche lobe. If both the primary and the secondary overflow their Roche lobes, common-envelope evolution will occur. Our model has five parameters: (1) the final mass ratio ({dollar}msb1/msb2{dollar}) of the system after mass transfer stops, (2) the fraction of mass lost by the primary that is transferred to the secondary, (3) the fraction of specific angular momentum carried away by mass lost from the system, (4) the magnitude of the kick velocity given to the remnant neutron star after a core collapse supernova explosion, and (5) the minimum core mass that will explode as a core collapse supernova, after the explosion. The first three model parameters, which determine how much of the primary's envelope will be stripped and how much of it is transferred to the secondary, greatly affects the kinematics of the HMXB's, runaway OB and proto-Be stars produced by our model. The velocities of the runaway O stars produced by our model agree well with observations although the velocities of the X-ray binaries produced are too high. The kinematics of the pulsars produced by our model are strongly dependent on the magnitude of the kick velocity used while the effect of the extent of mass transfer is negligible. The kick velocity does not change the runaway OB star velocities greatly, but does strongly affect the number of HMXB's and proto-Be stars produced. We find that a kick velocity of around 150 km s{dollar}sp{lcub}-1{rcub}{dollar} is needed to be consistent with current surveys of pulsar velocities.
Keywords/Search Tags:Runaway OB, Model, Velocities, Velocity, Mass, Star
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