Numerical simulations, analytical expressions, and observations of apsidal and nodal superhumps

Details Numerical simulations, analytical expressions, and observations of apsidal and nodal superhumps Numerical simulations, analytical expressions, and observations of apsidal and nodal superhumps

Oct 2004

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004phdt........15m&link_type=abstract

Thesis (PhD). FLORIDA INSTITUTE OF TECHNOLOGY, Source DAI-B 65/04, p. 1909, Oct 2004, 256 pages.

Physics

Scientific paper

We use theory and numerical simulations, as constrained by observations, to better understand nodal and apsidal superhumps in Cataclysmic Variable (CV) systems. We verify the postulated tilted accretion disk theory by generating artificial light curves and associated Fourier transforms containing nodal and/or apsidal superhumps from numerical simulations of tilted accretion disks. We consider main sequence secondaries only. Apsidal superhumps are adequately described by dynamical motions of particles in a progradely precessing accretion disk due to a tidally perturbing secondary less the pressure effects due to the spiral arms. Nodal superhumps are numerically and kinematically described by the secondary tidally inducing a retrograde precession of a disk tilted out of the orbital plane ˜3° 10°. We suggest that disk tilt is neither caused by thermal instabilities nor tidal instabilities that induce apsidal precession. We find that the disk cannot remain tilted by a steady accretion rate typical of SU UMa's that strikes the inner disk. We find that the accretion disk tilt is a pattern that the disk and secondary pass through, and that the secondary maintains facing the minor axis of the elliptical accretion disk. We extend the mass ratio lower to q = 0.025 and the upper limit to q = 0.35 for apsidally precessing systems. We find no mass ratio limit on nodal precession in our simulations with an imposed disk tilt. Our analytical expressions and numerical simulations agree with observations, on average. For nodal precession, we apply the lunisolar precessional theory to CVs. The ratio of our analytical expressions and numerical simulations of apsidal to-nodal precessions is nearly 2:1, the same ratio found in observations and in the lunisolar precessional theory. We question whether V1159 Ori and ER UMa truly are nodally precessing systems. We suggest that TV Col has a non-main sequence secondary and that an extended campaign be conducted. We find that primary mass is the main descriminator in the apsidal and nodal precessions. The different physics to apsidal and nodal precession lead to primary mass estimates within ˜0.2 M&sun; and mass ratios within ˜0.02. We provide ballpark primary and secondary mass estimates of CV apsidally and nodally precessing systems.

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