@article{b5413f0403434aa3999b5146afe74310,
title = "Effective temperatures of cataclysmic-variable white dwarfs as a probe of their evolution",
abstract = "We present HST spectroscopy for 45 cataclysmic variables (CVs), observed with HST/COS and HST/STIS. For 36 CVs, the white dwarf is recognisable through its broad Ly α absorption profile and we measure the white dwarf effective temperatures (Teff) by fitting the HST data assuming log g = 8.35, which corresponds to the average mass for CV white dwarfs (≃0.8M⊙). Our results nearly double the number of CV white dwarfs with an accurate temperature measurement. We find that CVs above the period gap have, on average, higher temperatures (〈 Teff〉 ≃ 23 000 K) and exhibit much more scatter compared to those below the gap (〈Teff〉 ≃ 15 000 K). While this behaviour broadly agrees with theoretical predictions, some discrepancies are present: (i) all our new measurements above the gap are characterized by lower temperatures (Teff ≃ 16 000-26 000 K) than predicted by the present-day CV population models (Teff ≃ 38 000-43 000 K); (ii) our results below the gap are not clustered in the predicted narrow track and exhibit in particular a relatively large spread near the period minimum, which may point to some shortcomings in the CV evolutionary models. Finally, in the standard model of CV evolution, reaching the minimum period, CVs are expected to evolve back towards longer periods with mean accretion rates M ≲ 2 × 10-11M⊙ yr-1, corresponding to Teff ≲ 11 500 K. We do not unambiguously identify any such system in our survey, suggesting that this major component of the predicted CV population still remains elusive to observations.",
keywords = "Novae, cataclysmic variables, Stars: fundamental parameters, Ultraviolet: stars, White dwarfs",
author = "Pala, {A. F.} and G{\"a}nsicke, {B. T.} and D. Townsley and D. Boyd and Cook, {M. J.} and {De Martino}, D. and P. Godon and Haislip, {J. B.} and Henden, {A. A.} and I. Hubeny and Ivarsen, {K. M.} and S. Kafka and C. Knigge and LaCluyze, {A. P.} and Long, {K. S.} and Marsh, {T. R.} and B. Monard and Moore, {J. P.} and G. Myers and P. Nelson and D. Nogami and A. Oksanen and R. Pickard and G. Poyner and Reichart, {D. E.} and {Rodriguez Perez}, D. and Schreiber, {M. R.} and J. Shears and Sion, {E. M.} and R. Stubbings and P. Szkody and M. Zorotovic",
note = "Funding Information: This work is based on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with programme GO-9357, GO-9724, GO-12870 and GO-13807. We gratefully acknowledge the variable star observations from the AAVSO International Database contributed by observers worldwide and used in this research. We are indebted to the global amateur community for their outstanding support, which made the HST survey possible. We are also extremely grateful for the tireless efforts of the operations and COS teams at STScI, including Amber Armstrong, Elena Mason, Charles Proffitt, Nolan Walborn and Alan Welty, in implementing this challenging programme. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement no. 320964 (WDTracer). DDM acknowledges support from ASI-INAF I/037/12/0. MRS thanks for support from Fondecyt (1141269). TRM acknowledges STFC ST/L000733. PG is pleased to thank William (Bill) Blair for his kind hospitality at the Rowland Department of Physics and Astronomy at the Johns Hopkins University, Baltimore, MD. This research has made use of the APASS data base, located at the AAVSO web site. Funding for APASS has been provided by the Robert Martin Ayers Sciences Fund. This research has made use of the NASA/IPAC Extragalactic Database (NED), which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration. Publisher Copyright: {\textcopyright} 2016 The Authors.",
year = "2017",
month = apr,
day = "21",
doi = "10.1093/mnras/stw3293",
language = "English (US)",
volume = "466",
pages = "2855--2878",
journal = "Monthly Notices of the Royal Astronomical Society",
issn = "0035-8711",
publisher = "Oxford University Press",
number = "3",
}