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arXiv 2103.03644astro-ph.SR
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再论食双星。纸张IV。演化的G-型系统AN Camelopardalis

Rediscussion of eclipsing binaries. Paper IV. The evolved G-type system AN Camelopardalis

John Southworth

备注：
Accepted for publication in The Observatory. 14 pages, 5 black and white figures, 4 tables
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摘要：

安凸轮是一个很少研究的食双星包含有点演变的组成部分，在轨道上的周期为21.0 d和偏心率为0.47。1977年发表了基于光电径向速度的光谱轨道。使用TESS卫星在三个部分观测了AN Cam：数据是以长节奏模式获得的，涵盖九次日食。通过模拟这些数据和公布的径向速度，我们得到的质量为1.380 +/- 0.021 Msun和1.402 +/- 0.025 Msun，半径为2.159 +/- 0.012 Rsun和2.646 +/- 0.014 Rsun。我们还从这些数据和最近的最低光时间得到了精确的轨道星历，但发现假设一个恒定的轨道周期，旧的最低光时间不能拟合。这可能是由天体物理或仪器效应引起的;即将到来的TESS观测将有助于调查这一问题。我们使用盖亚EDR 3视差和光学/红外视星等来测量6050 +/- 150 K和5750 +/- 150 K的有效温度：主星比它的伴星更热，但更小，质量更小。与理论模型的比较表明，该系统具有近似太阳的化学成分，年龄为3.3 Gyr。尽管它们的质量相似，但这两颗恒星处于不同的演化状态：主星接近主序星寿命的终点，而主星现在是亚巨星。AN凸轮是一个有前途的候选人约束的对流核心过冲在1.4 Msun星的强度。

英文摘要：

AN Cam is a little-studied eclipsing binary containing somewhat evolved components in an orbit with a period of 21.0 d and an eccentricity of 0.47. A spectroscopic orbit based on photoelectric radial velocities was published in 1977. AN Cam has been observed using the TESS satellite in three sectors: the data were obtained in long-cadence mode and cover nine eclipses. By modelling these data and published radial velocities we obtain masses of 1.380 +/- 0.021 Msun and 1.402 +/- 0.025 Msun, and radii of 2.159 +/- 0.012 Rsun and 2.646 +/- 0.014 Rsun. We also derive a precise orbital ephemeris from these data and recent times of minimum light, but find that the older times of minimum light cannot be fitted assuming a constant orbital period. This could be caused by astrophysical or instrumental effects; forthcoming TESS observations will help the investigation of this issue. We use the Gaia EDR3 parallax and optical/infrared apparent magnitudes to measure effective temperatures of 6050 +/- 150 K and 5750 +/- 150 K: the primary star is hotter but smaller and less massive than its companion. A comparison with theoretical models indicates that the system has an approximately solar chemical composition and an age of 3.3 Gyr. Despite the similarity of their masses the two stars are in different evolutionary states: the primary is near the end of its main-sequence lifetime and the secondary is now a subgiant. AN Cam is a promising candidate for constraining the strength of convective core overshooting in 1.4 Msun stars.

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