伴随行星的白矮星对次巨行星埃帕星网室的演化限制
Evolutionary Constraints on the Planet-Hosting Subgiant Epsilon Reticulum from its White Dwarf Companion
摘要：
从演化程度更高的白矮星次级恒星的角度研究了行星宿主和双星系统网壳星（HD 27442）。恒星的参数是由巴耳末线光谱，引力红移和立体角的组合。这三种方法合在一起产生了迄今为止最准确的伴星物理描述：Teff= 15，310 \pm 350 K和M=0.60 \pm 0.02 Msol。主序星后的质量损失表明，当前的双星距离已经从当前主序星形成行星时的原始状态增加了1.6倍，这意味着a0 > 150 AU，并将稳定的行星限制在15-20 AU内，而双星的离心率为e=0.5。自从第一次探测到伴星以来已经过去了近80年，在双星系统中，边缘轨道运动可能是明显的，这表明它是一个接近边缘的配置，i > 70度，尽管有很大的不确定性。如果正确的话，所有已知的天体都是共面的，那么行星HD 27442 b的质量将在1.66到1.77兆焦耳之间。在DA白矮星中寻找光球金属没有发现，因此没有明确的迹象表明现存的行星系统绕着以前更大质量的次级行星运行。然而，如果通过光谱拟合得出的白矮星质量是正确的，那么它的演化可能受到渐近巨星分支期间与内行星相互作用的影响。根据巨行星和星周碎片的频率与恒星质量的函数关系，原始主星不太可能没有行星，因为至少有一颗行星绕着它的质量较小的兄弟轨道运行。
英文摘要：
The planet-hosting and Sirius-type binary system epsilon Reticulum (HD 27442) is examined from the perspective of its more evolved white dwarf secondary. The stellar parameters are determined from a combination of Balmer line spectroscopy, gravitational redshift, and solid angle. These three methods conspire to yield the most accurate physical description of the companion to date: Teff=15,310 \pm 350 K and M=0.60 \pm 0.02 Msol. Post-main sequence mass loss indicates the current binary separation has increased by a factor of 1.6 from its primordial state when the current primary was forming its planet(s), implying a0 > 150 AU and constraining stable planets to within 15-20 AU for a binary eccentricity of e=0.5. Almost 80 years have passed since the first detection of the stellar companion, and marginal orbital motion may be apparent in the binary, suggesting a near edge-on configuration with i > 70 deg, albeit with substantial uncertainty. If correct, and all known bodies are coplanar, the mass of the planet HD 27442b is bound between 1.66 and 1.77 Mjup. A search for photospheric metals in the DA white dwarf yields no detections, and hence there is no clear signature of an extant planetary system orbiting the previously more massive secondary. However, if the white dwarf mass derived via spectral fitting is correct, its evolution could have been influenced by interactions with inner planets during the asymptotic giant branch. Based on the frequency of giant planets and circumstellar debris as a function of stellar mass, it is unlikely that the primordial primary would be void of planets, given at least one orbiting its less massive sibling.
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