The mass of the white dwarf in YY Dra (=DO Dra): Dynamical measurement and comparative study with X-ray estimates
: Álvarez-Hernández, A.; Torres, M. A. P.; Shahbaz, T.; Rodriguez-Gil, P.; Gazeas, K. D.; Sánchez-Sierras, J.; Jonker, P. G.; Corral-Santana, J. M.; Acosta-Pulido, J. A.; Hakala, P.
Publisher: EDP SCIENCES S A
: LES ULIS CEDEX A
: 2024
: Astronomy and Astrophysics
: ASTRONOMY & ASTROPHYSICS
: ASTRON ASTROPHYS
: A218
: 690
: 12
: 0004-6361
: 1432-0746
DOI: https://doi.org/10.1051/0004-6361/202451094
: https://doi.org/10.1051/0004-6361/202451094
: https://research.utu.fi/converis/portal/detail/Publication/459169450
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 sini=103 +/- 2 kms(-1). Through simultaneous modelling of the radial velocity and light curves, we derived values for the radial velocity semi-amplitude of the donor star, K-2= 188-2+1 K- 2= 188( - 2 )(+ 1) $ K-2 = 188(-2)(+1)km s(-1), the donor to white dwarf mass ratio, q =M-2/M-1 = 0.62 +/- 0.02, and the orbital inclination, i=42 degrees-1 degrees+2 degrees. These binary parameters yield dynamical masses of M-1 = 0.99(-0.09)(+0.10) M-circle dot M-1= 0 . 99( -0.09 )+M- 0.10 (circle dot) M1 = 0.99<^>{+0.10}_{-0.09} \, \mathrm{M}_{\odot} $ and M2 = 0.62-0.06+0.07 M circle dot M 2 = 0 . 62 - 0.06 + 0.07 M circle dot $ M_2 = 0.62<^>{+0.07}_{-0.06} \, \mathrm{M}_{\odot} $ (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.
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This work was supported by the Agencia Estatal de Investigación del Ministerio de Ciencia e Innovación (MCIN/AEI) and the European Regional Development Fund (ERDF) under grant PID2021-124879NB-I00. MAPT acknowledges to have received support via a Ramón y Cajal Fellowship (RYC-2015-17854). PR-G acknowledges support from the Consejería de Economía, Conocimiento y Empleo del Gobierno de Canarias and the European Regional Development Fund (ERDF) under grant with reference ProID2021010132. P.G.J. has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant agreement No. 101095973).
