标题： 确定相互作用双星的光谱质量比：应用于X射线新星天蝎座1994 显示英文标题

标题： Determining the spectroscopic mass ratio in interacting binaries: Application to X-Ray Nova Sco 1994

摘要： 我们提出一种模型，通过直接拟合观测光谱与合成光谱来确定相互作用双星的质量比。 我们直接使用NextGen模型大气强度，这些是目前针对冷恒星最全面和详细的模型。 我们通过将合成光谱纳入次级星的Roche几何结构中，充分考虑次级星光球层上温度和重力的变化。 因此，我们确定了次级星的确切旋转展宽光谱，从而消除了对边缘暗化定律的需求及其相关不确定性。 作为示例，我们确定了广泛研究的软X射线暂现源Nova Sco 1994的质量比。 为了获得不依赖于旋转速度分布和边缘暗化系数假设的更精确的质量比测定，我们使用模型计算出确切的旋转展宽模型光谱，并将其直接与Nova Sco 1994的中等分辨率观测光谱进行比较。 我们确定Nova Sco 1994的质量比为0.419±0.028（90%置信度），这是X射线双星中最为精确的质量比测定结果。 这一结果结合双星质量函数和倾斜角给出了一个改进的黑洞质量为5.99±0.42 Mo（90%置信度）。 我们还进行了模拟，结果显示，对于F型次级星，标准旋转速度分布以及线边缘暗化系数的零值和连续谱值给出的q值会将使用完整几何处理得到的值包含在内。 显示英文摘要

摘要： We present a model for determining the mass ratio in interacting binaries by directly fitting the observed spectrum with synthetic spectra. We make direct use of NextGen model atmospheres intensities which are the most comprehensive and detailed models available for cool stars. We fully take into account the varying temperature and gravity across the secondary star's photosphere, by incorporating the synthetic spectra into the secondary star's Roche geometry. As a result, we determine the exact rotationally broadened spectrum of the secondary star and so eliminate the need for a limb-darkening law, and the uncertainties associated with it. As an example we determine the mass ratio for the well studied soft X-ray transient Nova Sco 1994. In order to obtain a more accurate determination of the mass ratio, which does not depend on assumptions about the rotation profile and limb-darkening coefficients, we use our model to compute the exact rotationally broadened model spectrum, which we compare directly with the observed intermediate resolution spectrum of Nova Sco 1994. We determine the mass ratio of Nova Sco 1994 to be 0.419+/-0.028 (90 percent confidence), which is the most accurate determination of the binary mass ratio in an X-ray binary. This result combined with the binary mass function and inclination angle gives a refined black hole mass of 5.99+\-0.42 Mo (90 percent confidence). We also perform simulations which show that, for an F-type secondary star, the standard rotation profile with zero and continuum value for the line limb-darkening coefficient gives a value for q that brackets the value found using the full geometrical treatment.