The Donor Stars of Cataclysmic Variables

We construct a complete, semi-empirical donor sequence for CVs with orbital periods less than 6 hrs. All key physical and photometric parameters of CV secondaries (along with their spectral types) are given as a function of P_orb along this sequence. The main observational basis for our donor sequence is an empirical mass-radius relation for CV secondaries. We present an optimal estimate for this relation that ensures consistency with the observed locations of the period gap and the period minimum. We also present new determinations of these periods, finding P_{gap, upper edge} = 3.18 +/- 0.04 hr, P_{gap, lower edge} = 2.15 +/- 0.03 hr and P_{min} = 76.2 +/- 1.0 min. We then test the donor sequence by comparing observed and predicted spectral types (SpTs) as a function of orbital period. To this end, we update the SpT compilation of Beuermann et al. and show explicitly that CV donors have later SpTs than main sequence (MS) stars at all orbital periods. The semi-empirical donor sequence matches the observed SpTs very well, implying that the empirical M2-R2 relation predicts just the right amount of radius expansion. We finally apply the donor sequence to the problem of distance estimation. Based on a sample of 22 CVs with trigonometric parallaxes, we show that the donor sequence correctly traces the envelope of the observed M_{JHK}-P_{orb} distribution. Thus robust lower limits on distances can be obtained from single-epoch infrared observations.

[1]  J. R. Thorstensen,et al.  PARALLAX AND DISTANCE ESTIMATES FOR TWELVE CATACLYSMIC VARIABLE STARS , 2008, 0809.1550.

[2]  K. Pearson.  Superhumps: confronting theory with observation , 2006, astro-ph/0605743.

[3]  Cambridge,et al.  The dynamics of eccentric accretion discs in superhump systems , 2006, astro-ph/0602492.

[4]  J. Davy Kirkpatrick,et al.  New spectral types L and T , 2005 .

[5]  U. Southampton,et al.  ULTRACAM photometry of the eclipsing cataclysmic variables XZ Eri and DV UMa , 2004, astro-ph/0409184.

[6]  H. Ritter,et al.  Long-term evolution of compact binaries with irradiation feedback , 2004, astro-ph/0403306.

[7]  B. Gaensicke,et al.  An HST parallax of the distant cataclysmic variable V1223 Sgr, its system parameters, and accretion rate , 2004, astro-ph/0402548.

[8]  J. J. Johnson,et al.  An Astrometric Calibration of the MV-Porb Relationship for Cataclysmic Variables based on Hubble Space Telescope Fine Guidance Sensor Parallaxes , 2004 .

[9]  C. Mauche.  Accretion-powered Compact Binaries , 2003 .

[10]  G. F. Benedict,et al.  A precise HST parallax of the cataclysmic variable EX Hydrae, its system parameters, and accretion rate , 2003, astro-ph/0309530.

[11]  L. Bildsten,et al.  Measuring White Dwarf Accretion Rates via Their Effective Temperatures , 2003, astro-ph/0309208.

[12]  J. Thorstensen,et al.  Superhumps in Cataclysmic Binaries. XXIV. Twenty More Dwarf Novae , 2003, astro-ph/0309100.

[13]  F. Allard,et al.  Evolutionary models for cool brown dwarfs and extrasolar giant planets. The case of HD 209458 , 2003, astro-ph/0302293.

[14]  H. Ritter,et al.  Catalogue of Cataclysmic Binaries, Low-Mass X-Ray Binaries and Related Objects , 1984, astro-ph/0301444.

[15]  R. Nichol,et al.  Cataclysmic Variables from The Sloan Digital Sky Survey. I. The First Results , 2004 .

[16]  W. H. Fenton,et al.  QZ Serpentis: A Dwarf Nova with a 2 Hour Orbital Period and an Anomalously Hot, Bright Secondary Star , 2002, astro-ph/0206435.

[17]  R. Mennickent,et al.  A search for brown dwarf like secondaries in cataclysmic variables – II , 2002, astro-ph/0206343.

[18]  R. Webbink,et al.  Cataclysmic variable evolution: AM Her binaries and the period gap , 2002, astro-ph/0204351.

[19]  W. H. Fenton,et al.  1RXS J232953.9+062814: A Dwarf Nova with a 64 Minute Orbital Period and a Conspicuous Secondary Star , 2002, astro-ph/0201487.

[20]  F. Allard,et al.  Evolutionary models for low-mass stars and brown dwarfs: uncertainties and limits at very young ages , 2001, astro-ph/0111385.

[21]  S. Rappaport,et al.  Cataclysmic variables with evolved secondaries and the progenitors of AM CVn stars , 2001, astro-ph/0109171.

[22]  W. Jefferys,et al.  Interferometric Astrometry with Hubble Space Telescope Fine Guidance Sensor 3: The Parallax of the Cataclysmic Variable TV Columbae , 2001, astro-ph/0107026.

[23]  F. Allard,et al.  The Limiting Effects of Dust in Brown Dwarf Model Atmospheres , 2001, astro-ph/0104256.

[24]  J. Carpenter.  Color Transformations for the 2MASS Second Incremental Data Release , 2001, astro-ph/0101463.

[25]  J. Huston,et al.  Uncertainties of predictions from parton distribution functions. I. The Lagrange multiplier method , 2001, hep-ph/0101051.

[26]  P. H. Hauschildt,et al.  Infrared Spectra and Spectral Energy Distributions of Late M and L Dwarfs , 2000, astro-ph/0010174.

[27]  U. Kolb,et al.  Mass estimates in short-period compact binaries , 2000, astro-ph/0009458.

[28]  F. Allard,et al.  TiO and H2O Absorption Lines in Cool Stellar Atmospheres , 2000, astro-ph/0008465.

[29]  F. Allard,et al.  Evolutionary Models for Very Low-Mass Stars and Brown Dwarfs with Dusty Atmospheres , 2000, astro-ph/0005557.

[30]  U. Kolb,et al.  On the late spectral types of cataclysmic variable secondaries , 2000, astro-ph/0004310.

[31]  D. Ciardi,et al.  Infrared spectroscopy of cataclysmic variables — III. Dwarf novae below the period gap and nova-like variables , 2000, astro-ph/0001525.

[32]  K. Beuermann.  Secondary stars in CVs - the observational picture , 1999, astro-ph/9909141.

[33]  U. Kolb,et al.  Secondary stars in CVs: the theoretical perspective , 1999, astro-ph/9906449.

[34]  H. Duerbeck.  Hipparcos parallaxes of cataclysmic binaries and the quest for their absolute magnitudes , 1999 .

[35]  U. Kolb,et al.  Brown dwarfs and the cataclysmic variable period minimum , 1999, astro-ph/9906448.

[36]  W. Jefferys,et al.  Astrometry with Hubble Space Telescope Fine Guidance Sensor 3: The Parallax of the Cataclysmic Variable RW Triangulum , 1999, astro-ph/9905284.

[37]  David A. Smith,et al.  The secondary stars in cataclysmic variables and low-mass X-ray binaries , 1998 .

[38]  J. Patterson.  Late Evolution of Cataclysmic Variables , 1998 .

[39]  F. Allard,et al.  The NextGen Model Atmosphere Grid for 3000 ≤ Teff ≤ 10,000 K , 1998, astro-ph/9807286.

[40]  Graham Berriman,et al.  Infrared Spectra of Low-Mass Stars: Toward a Temperature Scale for Red Dwarfs , 1996 .

[41]  H. Ritter,et al.  An analytic approach to the secular evolution of cataclysmic variables , 1996 .

[42]  B. Warner.  The Cataclysmic Variable Stars , 1996 .

[43]  B. Warner.  Cataclysmic Variable Stars by Brian Warner , 1995 .

[44]  Pierre Bergeron,et al.  PHOTOMETRIC CALIBRATION OF HYDROGEN- AND HELIUM-RICH WHITE DWARF MODELS , 1995 .

[45]  T. Ramseyer.  The K-band surface brightness of late-type stars and the distance to cataclysmic variables , 1994 .

[46]  Todd J. Henry,et al.  The mass-luminosity relation for stars of mass 1.0 to 0.08 solar mass , 1993 .

[47]  D. Jones,et al.  The 8190-A sodium doublet in cataclysmic variables III. Too cool for credibility. , 1990 .

[48]  D. Jones,et al.  The 8190-A sodium doublet in cataclysmic variables - II. Too cool for comfort. , 1990 .

[49]  G. Rieke,et al.  The interstellar extinction law from 1 to 13 microns. , 1985 .

[50]  J. Patterson,et al.  The evolution of cataclysmic and low-mass X-ray binaries. , 1984 .

[51]  S. Rappaport,et al.  A new technique for calculations of binary stellar evolution, with application to magnetic braking , 1983 .

[52]  G. Neugebauer,et al.  Erratum - Infrared Standard Stars , 1982 .

[53]  G. Neugebauer,et al.  Infrared standard stars , 1982 .

[54]  J. Bailey.  The distances of cataclysmic variables , 1981 .

[55]  Bohdan Paczynski,et al.  Evolutionary Processes in Close Binary Systems , 1971 .