Asymmetries in the Envelopes of Wolf-Rayet Components of Close Binaries

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view Abstract Citations (3) References (6) Co-Reads Similar Papers Volume Content Graphics Metrics Export Citation NASA/ADS Asymmetries in the Envelopes of Wolf-Rayet Components of Close Binaries Limber, D. Nelson Abstract Idealized dynamical models, based upon different ad hoc -centered force laws for both the radiative and hydrodynamic forces, are used to study the effects of close companions in giving rise to geometrical and dynamical asymmetries in W-R envelopes These effects are found to be significant for the envelopes of that important class of dynamical models that now appears most promising for describing the phenomenon: envelopes for which the outward velocities increase from photospheric values that are small to values at five or more KR radii that are large, both relative to the absolute orbital speed of the W-R component. This same class of models appears to be consistent with the observations presently available insofar as these asymmetries are concerned and insofar as occultation effects are concerned. I. INTkODUCTION Castor has pointed out in a recent paper (1970) that ilson's transit-time effect ( rilson 1942) for the ?\ ( V-R) components of close binaries does not exist, at least not in the form presented by riIson in which the effect would exist even in the absence of inhomogeneities in the gravitational field of the companion. Castor has further shown that, even when such inhomogeneities are taken into account, the dynamical and geometrical asymmetnes in the envelope of the important V-R component of the close-binary system V444 Cygni are small-being comfortably helow the limits of detectability in the existing observations-4or the case in which the envelope matter is assumed to he radially ejected with speeds greater than 1000 km sec ' from a surface centered on the W-R component with a radius of about 5 o and is assumed to he suhjected, subsequently, only to the gravitational forces of the two stars. In the present paper the problem of the dynamical and geometrical asymmetries in the envelopes of the J-R components of close binaries will he carried further. The primary aim of this study is to ohtain estimates of the envelope asymmetries to he expected on the assumption that the dynamics of the envelopes of ? J-R stars corresponds more closely to accelerated outward motions from initial velocities at the surfaces of the V-R stars that are smaller than 1000 km sec ' to velocities at five or more V-R radii that are about 1500 km than to high-speed ejection from the V-R surfaces at 1000 km sec-1 or more followed by gravitational deceleration due to the J-R stars. However, before we turn to this study, it should be noted that there is the possibility that there are significant forces per unit mass arising from the companion that are very different for the envelope matter than for the V-R star. Such forces would include the mechanical force due to the radiation field of the companion. If such forces were of the order of the gravitational force due to the companion, they could play a significant role in introducing asymmetries into the envelope dynamics. If, as an extreme example, the forces on elements of mass in the envelopes resulting from the radiation and gravitational fields of both the V-R star and the companion exactly canceled one another, then-if eclipse effects by the -R star on the radiation field of the companion are neglected-the net force exerted on the envelope matter would vanish, and the envelope kinematics would be just those postulated in Wilson's simple treatment of the transittime effect. There will be some effect of this kind operating in the actual systems. However, its magniftide could not closely approach that of the extreme example just considered. Such effects will not be further considered here. 337 Publication: The Astrophysical Journal Pub Date: January 1971 DOI: 10.1086/150773 Bibcode: 1971ApJ...163..337L full text sources ADS | data products SIMBAD (2)