Journal Article

Distances and absolute magnitudes of dwarf novae: murmurs of period bounce

Joseph Patterson

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 4, pages 2695-2716
Published in print March 2011 | ISSN: 0035-8711
Published online March 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17881.x
Distances and absolute magnitudes of dwarf novae: murmurs of period bounce

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We redetermine the relationship between absolute magnitude and orbital period for dwarf novae, based on 46 stars with good distance estimates. This improves upon Warner’s previous relation, building upon today’s improved estimates of distance and binary inclination, and greater wavelength coverage. Together with other distance and dynamical constraints, this calibration is then applied to a set of ∼300 known or likely dwarf novae of short orbital period, to study the dependence of quiescent Mv, time-averaged Mv, mass ratio q and white-dwarf temperature TWD, on Porb. These distributions show that stars become much fainter as they approach the minimum Porb, and appear to show evolutionary tracks as the secondary is whittled down by mass-loss. Stars on the lower branch have the expected properties of ‘period bouncers’– with a feeble secondary, faint accretion light, cool white dwarf and long recurrence time between eruptions. Period bounce seems to occur at a mass of 0.058 ± 0.008 Mo. Stars on the lower branch may also have higher velocities and heights above the Galactic plane, consistent with a greater age. Some are very nearby, despite strong selection effects discriminating against the discovery of these faint binaries accreting at very low rates. Period bouncers appear to be very common, and probably would dominate a complete census of cataclysmic variables.

Keywords: accretion, accretion discs; catalogues; stars: distances; stars: dwarf novae; stars: evolution

Journal Article.  18645 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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