Observations of Spin-down in Post-mass-transfer Stars and the Possibility for Blue Straggler Gyrochronology
Observations of Spin-down in Post-mass-transfer Stars and the Possibility for Blue Straggler Gyrochronology
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DOI：
10.3847/2041-8213/aaf4ed
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发表时间：
2018-12-20
影响因子：
7.9
通讯作者：
Sills, Alison
中科院分区：
文献类型：
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作者：
Leiner, Emily;Mathieu, Robert D.;Sills, Alison
蓝离散星和其他质量转移/碰撞产物可能由于质量转移、合并或碰撞形成期间的角动量转移而具有快速旋转速率。然而，人们对这些恒星随着年龄的增长角动量的演化知之甚少。在这里，我们比较旋转速率和形成后的质量转移产品的角动量演化模型的主序（MS）恒星和碰撞形成的蓝色离散。在我们的样本中，我们包括在集群NGC 188和后质量转移GK MS星的领域，所有的双星与白色矮星（WD）的同伴的F-和G-型蓝离散。我们比较年龄来自WD冷却模型的光度旋转周期和/或光谱V正弦测量。我们证明，这些系统具有快速的旋转速率后不久形成。然后它们随着年龄的增长而旋转，就像标准的太阳型MS星一样。我们讨论了这一结果的物理意义，这表明，自旋后质量转移的明星可以描述的标准磁制动处方。这开启了使用陀螺年代学作为确定蓝离散星和其他后质量转移双星形成时间的方法的可能性。
Blue stragglers and other mass transfer/collision products are likely born with rapid rotation rates due to angular momentum transfer during mass-transfer, merger, or collisional formation. However, less is known about the angular momentum evolution of these stars as they age. Here we compare rotation rates and post-formation ages of mass-transfer products to models of angular momentum evolution for normal main-sequence (MS) stars and collisionally formed blue stragglers. In our sample, we include both F-and G-type blue stragglers in the cluster NGC 188 and post-mass-transfer GK MS stars in the field, all binaries with white dwarf (WD) companions. We compare ages derived from WD cooling models to photometric rotation periods and/or spectral v sin i measurements. We demonstrate that these systems have rapid rotation rates soon after formation. They then spin down as they age, much like standard solar-type MS stars do. We discuss the physical implications of this result, which suggests that the spin-down of post-mass transfer stars can be described by standard magnetic-braking prescriptions. This opens up the possibility of using gyrochronology as a method to determine the time since formation of blue straggler stars and other post-mass-transfer binaries.