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Evolutionary Sequences For Low- And-Intermediate-Mass X-Ray Binaries Ph. Podsiadlowski S. Rappaport E. D. Pfahl
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Introduction LMXBs: discovered 40 yr ago Porb<10 days No luminous companion stars The only one case confirmed: Cyg X-2 LMXBs may descend from IMXBs
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Binary Calculations Roche lobe radius: Mass transfer rate: Angular momentum loss:
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Binary Calculations
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(1): Systems evolving to long periods (2): Systems evolving to short periods (3): More massive systems Experiencing dynamical mass transfer and spiral-in Very few systems should be observable in the early rapid phase and X-ray binaries are mostly likely to have a relatively low mass secondary when they are observerd at the present epoch
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Thermal Timescale Mass Transfer Mass-radius exponents:
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In radiative stars, a large fraction of the envelope (in radius) contains very little mass
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The systems becomes temporarily detached when the H-burning shell stars to move into the region with a gradient in hydrogen abundance, established during the hydrogen core burning phase and the giant shrinks significantly
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The early mass transfer phase can be divided into two separate phases: (1):a phase of atmospheric Roche lobe overflow where the mass transfer rate increases exponentially, (2): a phase where the high-entropy material in the low-density envelope of the secondary is lost
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The drop in Pmin at 13 hr occurs for a model where the secondary has just exhausted hydrogen in the center at the beginning of mass transfer
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Application to The Population of X-Ray Binaries Issues: (1) how unique are the evolutionary paths we have found, (2) are types of systems suggested by other resonably long-lived phases of our binary evolutions represented in the observed binary X- ray source population (3) is our complete ensemble of binary evoltuion models consistent with the overall population of observed LMXBs and IMXBs?
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Application to Binary Millisecond Pulsars In the Galaxy plane, binary radio pulsars classes: (1):one major class involves systems with low-mass companions. (2):the ones with substantially more massive white dwarf companions (3):systems containing planetary mass companions (4):systems consist of a pair of neutron stars
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A outstanding problem: the birthrate problem Application to Binary Millisecond Pulsars
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