The dynamical mass of a classical Cepheid variable star in an eclipsing binary system
The dynamical mass of a classical Cepheid variable star in an eclipsing binary system
复制标题
食双星系统中经典造父变星的动力质量
作者：
G. Pietrzyński;I. B. Thompson;W. Gieren;D. Graczyk;G. Bono;A. Udalski;I. Soszyński;D. Minniti;B. Pilecki
恒星脉动理论提供了一种确定脉动的经典造父变星超巨星质量的方法--正是脉动导致了它们光度的变化。这样的脉动质量被发现比恒星演化理论推导出的质量要小：这就是造父变星的质量差异问题，而这个问题还没有解决。一个独立的，精确的动力学质量测定的经典造父变星星星（相对于第二型造父变星，低质量的恒星有着非常不同的演化历史）在一个联星系统中是需要的，以确定这是正确的。以前从银河系单线非食双星建立造父变星动力学质量的努力的准确度通常是15-30%（参考文献6，7），这不足以解决质量差异问题。尽管进行了许多观测工作，但迄今为止还没有在食双线双星中发现经典造父变星的可靠报道。在这里，我们报告发现一个经典造父变星在一个良好的分离，双线食双星在大麦哲伦云。我们确定的质量精度为1%，并表明它同意其脉动质量，提供了强有力的证据，脉动理论正确和精确地预测经典造父变星的质量。
Stellar pulsation theory provides a means of determining the masses of pulsating classical Cepheid supergiants—it is the pulsation that causes their luminosity to vary. Such pulsational masses are found to be smaller than the masses derived from stellar evolution theory: this is the Cepheid mass discrepancy problem, for which a solution is missing. An independent, accurate dynamical mass determination for a classical Cepheid variable star (as opposed to type-II Cepheids, low-mass stars with a very different evolutionary history) in a binary system is needed in order to determine which is correct. The accuracy of previous efforts to establish a dynamical Cepheid mass from Galactic single-lined non-eclipsing binaries was typically about 15–30% (refs 6, 7), which is not good enough to resolve the mass discrepancy problem. In spite of many observational efforts, no firm detection of a classical Cepheid in an eclipsing double-lined binary has hitherto been reported. Here we report the discovery of a classical Cepheid in a well detached, double-lined eclipsing binary in the Large Magellanic Cloud. We determine the mass to a precision of 1% and show that it agrees with its pulsation mass, providing strong evidence that pulsation theory correctly and precisely predicts the masses of classical Cepheids.