The minimum mass ratio for contact close binary systems of W Ursae Majoris-type

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The minimum mass ratio for contact close binary systems of W Ursae Majoris-type

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dc.contributor.advisor Atanacković, Olga
dc.contributor.author Arbutina, Bojan
dc.date.accessioned 2010-05-18T09:59:13Z
dc.date.available 2010-05-18T09:59:13Z
dc.date.issued 2009-06-26
dc.identifier.uri http://hdl.handle.net/123456789/716
dc.description.abstract The main research topic of this dissertation are extreme mass ratio contact close binary systems, q 0.1, of W Ursae Majoris (W UMa) type. These close binaries (CBs) represent an interesting class of objects in which ”normal”, approximately one solar mass main-sequence star is in contact with a significantly less massive companion, M2 ∼ 0.1 M . Earlier theoretical investigations of these systems found that there is a minimum mass ratio qmin = M2/M1 ≈ 0.085 − 0.095 (obtained for n = 3 polytrope - fully radiative primary) above which these CBs are stable and could be observed. If the mass ratio is lower than qmin, or, equivalently, if orbital angular momentum is only about three times larger than the spin angular momentum of a massive primary, a tidal instability develops (Darwin’s instability) forcing eventually the stars to merge into a single, rapidly rotating object (such as FK Com-type stars or blue stragglers). However, there appear to be some W UMa-type CBs with empirically obtained values for the mass ratio below the theoretical limit for stability. The aim of this dissertation is to try to resolve the discrepancy between theory and observations by considering rotating polytropes. By including in theory the effects of higher central condensation due to rotation we were able to reduce qmin to the new theoretical value qmin = 0.070 − 0.074, for the overcontact degree f = 0 − 1, which is more consistent with the observed population. Other candidate systems for stellar mergers such as AM CVn-type stars have also been discussed in the dissertation. en_US
dc.description.provenance Submitted by Dusan Vasiljevic (vdusan@matf.bg.ac.rs) on 2010-05-18T09:59:13Z No. of bitstreams: 1 phdBojanArbutina.pdf: 6326465 bytes, checksum: de32884ad7c76c61cbe20469b1c35765 (MD5) en
dc.description.provenance Made available in DSpace on 2010-05-18T09:59:13Z (GMT). No. of bitstreams: 1 phdBojanArbutina.pdf: 6326465 bytes, checksum: de32884ad7c76c61cbe20469b1c35765 (MD5) Previous issue date: 2009-06-26 en
dc.format.extent 300 en_US
dc.format.mimetype pdf en_US
dc.language.iso sr en_US
dc.publisher Faculty of Mathematics, University of Belgrade en_US
dc.title The minimum mass ratio for contact close binary systems of W Ursae Majoris-type en_US
mf.author.birth-date 1977
mf.title.original Minimalni odnos masa za kontaktne tesne dvojne sisteme tipa W Ursae Majoris en_US
mf.subject.area Astrophysics, Close Binary Systems en_US
mf.subject.keywords instabilities - binaries, close - blue stragglers - stars, late-type en_US
mf.contributor.committee Angelov, Trajko
mf.contributor.committee Đuraševic, Gojko
mf.university.en University of Belgrade en_US
mf.university.faculty Faculty of Mathematics en_US
mf.document.references 99 en_US
mf.document.pages vi + 100 en_US

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