HZ HER: STELLAR RADIUS FROM X-RAY ECLIPSE OBSERVATIONS, EVOLUTIONARY STATE, AND A NEW DISTANCE
HZ HER: STELLAR RADIUS FROM X-RAY ECLIPSE OBSERVATIONS, EVOLUTIONARY STATE, AND A NEW DISTANCE
复制标题
DOI：
10.1088/0004-637x/793/2/79
复制
发表时间：
2014-06
期刊：
影响因子：
--
通讯作者：
Denis A. Leahy;M. H. Abdallah
中科院分区：
文献类型：
--
作者：
Denis A. Leahy;M. H. Abdallah
本文分析了罗西x射线定时探测器（RXTE）对HZ Her/Her X-1中子星高月食的观测。日食的模型被用来测量中子星的伴星HZ Her的半径和大气尺度高度。半径为2.58-3.01 × 1011 cm，取决于系统倾角和质量比(q)，给定倾角和质量比的精度为1000分之一。我们将库鲁兹模型恒星大气模型拟合到存档的光学观测中。其未加热表面的有效温度（Teff）被确定在7720 K - 7865 K的2σ范围内，金属丰度（log （Z/Z☉））在−0.27到+ 0.03的范围内。模式大气表面通量和新半径产生到HZ Her/Her X-1的新距离，取决于系统倾角和q：最佳拟合值为6.1 kpc，上限为5.7 kpc，下限为7.0 kpc。我们计算了恒星演化模型的允许质量范围（从轨道参数）和允许金属丰度（从光谱拟合）。恒星模型与Teff和HZ Her的半径一致，有两个较窄的质量范围：2.15-2.20 M☉和2.35-2.45 M☉。这个较低的质量范围意味着中子星质量较低（1.3 M☉），而较高的质量范围意味着中子星质量较高（1.5-1.7 M☉）。
Observations of HZ Her/Her X-1 by the Rossi X-Ray Timing Explorer (RXTE) covering high state eclipses of the neutron star are analyzed here. Models of the eclipse are used to measure the radius and atmospheric scale height of HZ Her, the stellar companion to the neutron star. The radius is 2.58–3.01 × 1011 cm, depending on system inclination and mass ratio (q), with an accuracy of ∼1 part in 1000 for given inclination and q. We fit Kurucz model stellar atmosphere models to archival optical observations. The resulting effective temperature (Teff) of the unheated face of HZ Her is determined to be in the 2σ range of 7720 K–7865 K, and metallicity (log (Z/Z☉)) in the range of −0.27 to +.03. The model atmosphere surface flux and new radius yield a new distance to HZ Her/Her X-1, depending on system inclination and q: a best-fit value of 6.1 kpc with upper and lower limits of 5.7 kpc and 7.0 kpc. We calculate stellar evolution models for the range of allowed masses (from orbital parameters) and allowed metallicities (from optical spectrum fits). The stellar models agree with Teff and the radius of HZ Her for two narrow ranges of mass: 2.15–2.20 M☉ and 2.35–2.45 M☉. This lower mass range implies a low neutron star mass (1.3 M☉), whereas the higher mass range implies a high neutron star mass (1.5–1.7 M☉).