Issue |
A&A
Volume 690, October 2024
|
|
---|---|---|
Article Number | A218 | |
Number of page(s) | 12 | |
Section | Astrophysical processes | |
DOI | https://doi.org/10.1051/0004-6361/202451094 | |
Published online | 10 October 2024 |
The mass of the white dwarf in YY Dra (=DO Dra): Dynamical measurement and comparative study with X-ray estimates
1
Instituto de Astrofísica de Canarias, E-38205 La Laguna, Tenerife, Spain
2
Departamento de Astrofísica, Universidad de La Laguna, E-38206 La Laguna, Tenerife, Spain
3
Section of Astrophysics, Astronomy and Mechanics, Department of Physics, National and Kapodistrian University of Athens, GR-15784 Zografos, Athens, Greece
4
Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010 6500 GL Nijmegen, The Netherlands
5
European Southern Observatory, Alonso de Córdova 3107, Casilla 19001 Vitacura, Santiago, Chile
6
Finnish Centre for Astronomy with ESO (FINCA), Quantum, University of Turku, Vesilinnantie 5, FI-20014 Turku, Finland
Received:
12
June
2024
Accepted:
18
July
2024
We present a dynamical study of the intermediate polar cataclysmic variable YY Dra based on time-series observations in the K band, where the donor star is known to be the major flux contributor. We covered the 3.97-h orbital cycle with 44 spectra taken between 2020 and 2022 and two epochs of photometry observed in 2021 March and May. One of the light curves was simultaneously obtained with spectroscopy to better account for the effects of irradiation of the donor star and the presence of accretion light. From the spectroscopy, we derived the radial velocity curve of the donor star metallic absorption lines, constrained its spectral type to M0.5–M3.5 with no measurable changes in the effective temperature between the irradiated and non-irradiated hemispheres of the star, and measured its projected rotational velocity vrot sin i = 103 ± 2 km s−1. Through simultaneous modelling of the radial velocity and light curves, we derived values for the radial velocity semi-amplitude of the donor star, K2 = 188−2+1 km s−1, the donor to white dwarf mass ratio, q = M2/M1 = 0.62 ± 0.02, and the orbital inclination, i = 42°−1°+2°. These binary parameters yield dynamical masses of M1 = 0.99−0.09+0.10 M⊙ and M2 = 0.62−0.06+0.07 M⊙ (68 per cent confidence level). As found for the intermediate polars GK Per and XY Ari, the white dwarf dynamical mass in YY Dra significantly differs from several estimates obtained by modelling the X-ray spectral continuum.
Key words: accretion, accretion disks / binaries : close / stars: dwarf novae / novae / cataclysmic variables / white dwarfs
© The Authors 2024
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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