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Mass transfer and eccentric orbit X-ray binary stars
Başlık:
Mass transfer and eccentric orbit X-ray binary stars
Yazar:
Boyle, Charles Burns, author.
ISBN:
9780438061101
Yazar Ek Girişi:
Fiziksel Tanımlama:
1 electronic resource (378 pages)
Genel Not:
Source: Dissertation Abstracts International, Volume: 76-08C.
Advisors: John Brown.
Özet:
The work presented in this thesis is concerned with the effects of an eccentric orbit on the binary model for Galactic X-ray sources. In the first chapter our present understanding of the processes of mass transfer and accretion occurring in close binaries, and in particular those containing a compact companion, are briefly reviewed. This review chapter serves the purpose of setting the scene and introduces the reader to some basic concepts. In Chapter 2, the variations in the mass accretion rate from a steady stellar wind caused by a finite orbital eccentricity are studied in detail and comparisons are made between the resulting modulations for two different stellar wind velocity profiles. In Chapter 3, an approximate analytical description of eccentric orbit 'Roche-lobe' overflow is developed, based on the assumption that the mass transfer rate can be instantaneously described in terms of overflow through a ' Roche-lobe' nozzle, analogously to the usual analyses for circular orbits. In Chapter 4, the dynamical behaviour of gas particles tidally stripped off of the primary star by a close compact companion in an eccentric orbit binary system is investigated by a numerical simulation. Having studied the effects of an eccentric orbit on mass transfer and accretion in the previous chapters, Chapter 5 deals with the resulting variation in optical linear polarization. In particular, the variations in the linear polarization of A0538-66 are discussed. Assuming this system is composed of an early type Be star with a neutron star companion, and that the polarization is produced by Thomson scattering in the envelope of the Be star, it is shown that the features of the polarization variability can be explained by a model in which the neutron star moves in a highly eccentric orbit (e ≥ 0.4) around its more massive companion. The effects of introducing physical variations into an otherwise purely geometric model are briefly studied and it is concluded that, with the exception of variations in the intrinsic optical intensity, the geometric variations of a highly eccentric orbit dominate the modulation of the optical polarization. In Chapter 6 it is pointed out that the eccentric orbit binary model proposed for the pulsating transient X-ray source, A0538-66 imply an apsidal motion period which, according to the "classical" formula, may be as low as 160 years. It is suggested that such a short period should show up as a small but significant difference between the sidereal binary period and the accurately known outburst cycle of 16.6515 +/- 0.0005 days, as the latter is attributed to passage of the neutron star through peri-astron. Therefore, after a single accurate determination of the sidereal binary period, rendered possible by the fast pulsar present the apsidal motion period can be immediately calculated. This would give important information on the internal structure of the massive, post mass-gaining B star in this system. A discussion of the evolutionary stage of A0538-66 is also given in this chapter and it is concluded that the system is rather old in the sense that the X-ray pulsar is spun back up to its present very short rotation period. As far as the fate of this system is concerned it is argued that a spiral in of the binary system in less than a few million years cannot be avoided. In the final chapter the major conclusions of the previous chapters are reviewed and the areas in which future work would be useful are pointed out.
Notlar:
School code: 0547
Konu Başlığı:
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Yer Numarası | Demirbaş Numarası | Shelf Location | Lokasyon / Statüsü / İade Tarihi |
---|---|---|---|
XX(684875.1) | 684875-1001 | Proquest E-Tez Koleksiyonu | Arıyor... |
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