[论文解读] Absolute dimensions of eclipsing binaries. XXIV. The Be star system DW Carinae, a member of the open cluster Collinder 228

J. Southworth, J. V. Clausen|ArXiv.org|Oct 13, 2006

Stellar, planetary, and galactic studies参考文献 53被引用 40

一句话总结

本研究利用斯特罗姆伦测光和高分辨率光谱学，对疏散星团科林德228中的食双星DW Carinae给出了精确的绝对物理参数。通过结合光曲线建模与光谱分解及径向速度分析，得到了两颗恒星的质量（11.34 ± 0.12 M☉ 和 10.63 ± 0.14 M☉）、半径（4.558 ± 0.045 R☉ 和 4.297 ± 0.055 R☉）、有效温度（27,900 ± 1,000 K 和 26,500 ± 1,000 K）以及距离模数（12.24 ± 0.12 mag），从而首次基于实测数据确定了科林德228星团的年龄（≈6 Myr）和金属量（Z ≈ 0.01）。

ABSTRACT

DW Carinae is a close but detached early B-type eclipsing binary in the young open cluster Cr 228. We have measured accurate physical properties of its components (masses and radii to 1%) and used these to derive the age, metallicity and distance of Cr 228. The rotational velocities of both components of DW Car are high, so we have investigated the performance of double-Gaussian fitting, one- and two-dimensional cross-correlation and spectral disentangling for measuring radial velocities in the presence of strong line blending. Gaussian and cross-correlation analyses require substantial corrections for the effects of line blending, which are only partially successful for cross-correlation. Disentangling is to be preferred because it does not assume anything about the shapes of spectral lines, and is not significantly affected by blending. Complete Stromgren uvby light curves have been obtained and accurate radii have been measured from them using the Wilson-Devinney program, constrained by an accurate spectroscopic light ratio. The Teffs and reddening have been found from Stromgren photometric calibrations. The masses and radii of DW Car are M_A = 11.34 +/- 0.12 Msun, R_A = 4.558 +/- 0.045 Rsun, M_B = 10.63 +/- 0.14 Msun and R_B = 4.297 +/- 0.055 Rsun. The Teffs are Teff_A = 27900 +/- 1000 K and Teff_B = 26500 +/- 1000 K, and the reddening is E(b-y) = 0.18 +/- 0.02 mag. Using empirical bolometric corrections we find a distance modulus of 12.24 +/- 0.12 mag for DW Car, which is in agreement with, and more accurate than, literature values for Cr 228. A comparison between the properties of DW Car and theoretical predictions is undertaken in the mass--radius and mass--Teff diagrams. Good agreement is found for an age of about 6 Myr and a metal abundance of Z approx 0.01 (abridged).

研究动机与目标

• 精确测定分离食双星DW Carinae的绝对物理参数。
• 利用该双星在疏散星团科林德228中的成员关系，独立推导星团的年龄、金属量和距离。
• 将理论恒星演化模型的准确性与来自同年龄、同金属量星团系统的实测数据进行对比验证。
• 评估并比较在强谱线重叠（由于高速自转）条件下，不同光谱径向速度测量技术的表现。

提出的方法

• 获取并建模了完整的斯特罗姆伦 uvby 光曲线，使用Wilson-Devinney程序确定半径和轨道参数。
• 对高分辨率FEROS光谱进行光谱分解，以获得径向速度，避免对谱线轮廓的假设。
• 测试了双高斯拟合及一维和二维互相关函数方法，但发现这些方法在谱线重叠情况下需进行显著修正。
• 利用精确的光谱亮度比约束Wilson-Devinney解，以减少参数空间中的局部极小值。
• 通过斯特罗姆伦测光校准确定有效温度，消光量为 E_{b-y} = 0.18 ± 0.02。
• 采用经验玻尔兹曼修正计算距离模数，并与文献值进行比较。

实验结果

研究问题

• RQ1 食双星DW Carinae两颗恒星的精确质量、半径和有效温度是多少？
• RQ2 基于该双星系统，疏散星团科林德228的距离、年龄和金属量是多少？
• RQ3 在高速自转且谱线严重重叠的恒星中，不同光谱径向速度测量技术的表现如何？
• RQ4 给定特定年龄和金属量时，理论恒星演化模型与DW Carinae实测性质的符合程度如何？
• RQ5 周围星周物质对光曲线有何贡献？是否影响所推导的物理参数？

主要发现

• DW Carinae中恒星A的质量为11.34 ± 0.12 M☉，半径为4.558 ± 0.045 R☉。
• 恒星B的质量为10.63 ± 0.14 M☉，半径为4.297 ± 0.055 R☉。
• 有效温度分别为A星27,900 ± 1,000 K，B星26,500 ± 1,000 K，由斯特罗姆伦测光校准得出。
• DW Carinae的距离模数为12.24 ± 0.12 mag，与先前文献估计一致且更为精确。
• 基于模型比较，星团科林德228的年龄约为6 Myr，金属量Z ≈ 0.01。
• 光谱分解法提供的径向速度最可靠，在谱线重叠情况下优于互相关与高斯拟合方法。