标题： YY Dra（=DO Dra）中白矮星的质量：动力学测量与X射线估计的比较研究 显示英文标题

标题： The mass of the white dwarf in YY Dra (=DO Dra): Dynamical measurement and comparative study with X-ray estimates

摘要： 我们基于在$K$波段的时间序列观测，对中间极性灾变变星 YY Dra 进行了动力学研究，其中已知供体恒星是主要的流量贡献者。 我们覆盖了$3.97$小时的轨道周期，拍摄了在$2020$和$2022$之间的 44 张光谱，以及 2021 年 3 月和 5 月两个时期的测光观测。 其中一条光曲线与光谱同时获得，以更好地考虑供体恒星的照射效应和吸积光的存在。 从光谱中，我们得到了供体恒星金属吸收线的径向速度曲线，将其光谱类型限定为 M0.5$-$M3.5，在恒星被照射和未被照射的半球之间没有有效温度的可测量变化，并测得了其投影旋转速度$v_\mathrm{rot} \sin i = 103 \pm 2 \, \mathrm{km}\,\mathrm{s}^{-1}$。 通过同时建模径向速度和光曲线，我们得到了供体恒星的径向速度半振幅$K_2 = 188^{+1}_{-2} \, \mathrm{km} \, \mathrm{s}^{-1}$，供体与白矮星的质量比$q=M_2/M_1 = 0.62 \pm 0.02$以及轨道倾角，$i={42^{\circ}}^{+2^{\circ}}_{-1^{\circ}}$。 这些双星参数给出了$M_{1} = 0.99^{+0.10}_{-0.09} \, \mathrm{M}_{\odot}$和$M_2 = 0.62^{+0.07}_{-0.06} \, \mathrm{M}_{\odot}$的动力学质量（$68$百分比置信水平）。 如同在中等极性系统 GK Per 和 XY Ari 中发现的那样，YY Dra 中白矮星的动力学质量与通过建模 X 射线谱连续体得到的几个估计值显著不同。 显示英文摘要

摘要： 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 $v_\mathrm{rot} \sin i = 103 \pm 2 \, \mathrm{km}\,\mathrm{s}^{-1}$. Through simultaneous modelling of the radial velocity and light curves, we derived values for the radial velocity semi-amplitude of the donor star, $K_2 = 188^{+1}_{-2} \, \mathrm{km} \, \mathrm{s}^{-1}$, the donor to white dwarf mass ratio, $q=M_2/M_1 = 0.62 \pm 0.02$, and the orbital inclination, $i={42^{\circ}}^{+2^{\circ}}_{-1^{\circ}}$. These binary parameters yield dynamical masses of $M_{1} = 0.99^{+0.10}_{-0.09} \, \mathrm{M}_{\odot}$ and $M_2 = 0.62^{+0.07}_{-0.06} \, \mathrm{M}_{\odot}$ ($68$ 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.