Starspots, chromospheric emission lines, and flares of zero-age main-sequence stars
Starspots, chromospheric emission lines, and flares of zero-age main-sequence stars
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零年龄主序星的星黑子、色球发射线和耀斑
DOI：
10.1093/pasj/psac069
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发表时间：
2022
影响因子：
2.3
通讯作者：
Oasa Yumiko
中科院分区：
文献类型：
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作者：
Yamashita Mai;Itoh Yoichi;Oasa Yumiko
零年龄主序星（ZAMS）被认为有巨大的恒星黑子，并显示出强烈的色球发射线，因为它们的表面磁场很强。我们讨论了ZAMS恒星的发电机活动，相对于它们的周期性的光变化所造成的一个恒星黑子和相对于色球发射线的强度。利用凌日系外行星巡天卫星（TESS）测光数据，获得了IC 2391和IC 2602中33颗ZAMS星的光变曲线。光变曲线可以分为以下四类：单一频率、可能的形状改变器、拍打器和复杂的可变性。光变曲线的振幅为0.001-0.145等，类似于昂宿星团中的ZAMS星。星点的覆盖范围是-。我们发现IC 2391、IC 2602和昴星团中的ZAMS星的光变和CaII发射线强度与最活跃的超耀斑星相当，比太阳大两个数量级，并且位于超耀斑星的外延上。这些结果表明，超级耀斑恒星将太阳的性质与年龄在3000万年到12000万年之间的ZAMS恒星的性质联系起来。光变曲线中具有单一频率或可能形状变化的ZAMS恒星往往具有大的光变化，表明大的光斑覆盖范围，以及饱和的CaII发射线强度。具有拍变或复杂变率的ZAMS星具有小的斑点覆盖范围和微弱的CaII发射线。在IC 2391和IC 2602的12颗ZAMS星的TESS光变曲线中，我们还探测到了21个耀斑，其中大多数恒星都有饱和的色球层CaII发射线。耀斑的能量估计为1033- 1035 erg，与超级耀斑的能量相当。
Zero-age main-sequence (ZAMS) stars are considered to have enormous starspots and show strong chromospheric emission lines because of their strong surface magnetic field. We discuss the dynamo activities of ZAMS stars with respect to their periodic light variation caused by a starspot and with respect to the strength of the chromospheric emission lines. The light curves of 33 ZAMS stars in IC 2391 and IC 2602 were obtained from TESS (Transiting Exoplanet Survey Satellite) photometric data. The light curves can be grouped into the following four categories: single frequency, possible shape changer, beater, and complex variability. The amplitudes of the light curves are 0.001–0.145 mag, similar to those of ZAMS stars in Pleiades. The starspot coverages are–. We found that the light variations and Caiiemission line strength of ZAMS stars in IC 2391, IC 2602, and the Pleiades cluster are as large as those of the most active superflare stars and two orders larger than those of the Sun, and are located on the extensions of the superflare stars. These results suggest that superflare stars link the properties of the Sun to those of the ZAMS stars of ages between 30 and 120 Myr. ZAMS stars with a single frequency or possible shape change in the light curve tend to have both large light variation, indicating large spot coverage, and saturated Caiiemission line strength. ZAMS stars with beat or complex variability have small spot coverage and a faint Caiiemission line. We also detected 21 flares in the TESS light curves of 12 ZAMS stars in IC 2391 and IC 2602, where most of these stars have saturated chromospheric Caiiemission lines. The energies of the flares are estimated to be ∼1033–1035erg, which is comparable with the energy of a superflare.