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Asteroseismic Analyses of Slowly Pulsating B Star KIC 8324482: Ultraweak Element Mixing beyond the Central Convective Core
The Astrophysical Journal ( IF 4.9 ) Pub Date : 2020-08-11 , DOI: 10.3847/1538-4357/aba430
Tao Wu 1, 2, 3, 4 , Yan Li 1, 2, 3, 4 , Zhen-min Deng 5 , Gui-fang Lin 1, 2, 3 , Han-feng Song 6 , Chen Jiang 7
Affiliation  

Asteroseismology is a powerful tool for probing the inner structure and determining the evolutionary status and the fundamental parameters of stars. The oscillation spectra of slowly pulsating B (SPB) stars show almost uniform period spans, whose pattern is sensitive to the structure of the μ-gradient shell beyond the central convective core and hence can be used to efficiently describe their shapes and constrain the convective core. The SPB star KIC8324482 was observed by Kepler for over 1470 days with a long-cadence pattern. Nearly equidistant period spacing patterns are found for the 14 connective dipolar modes that are extracted from the oscillation spectrum by Zhangetal. In the present work, we analyze them in depth with the χ-matching method and determine their χ-minimization models (CMMs). Based on those calculated CMMs, we find that KIC8324482 is a young ( = + t 20.96 age 1.28 3.85 Myr), metal-poor ( = + Fe H 0.6.9 0.115 0.176 [ ] dex), and intermediate-mass ( = M M 6.075 0.2500 0.1375 ) star with a convective core of = + M M 1.338 CC 0.091 0.057  in mass and = + R R 0.5175 CC 0.0103 0.0048  in radius and with a surface rotation velocity = + V 2.61 km s eq 0.11 0.13 1. The central hydrogen abundance is of = + X 0.5046 C 0.0074 . Asteroseismic analyses indicate that the “propagation time” of g-mode in KIC8324482 is of L = 0 + 276.85 0.47 1.26 μHz. To well match with the observed period spacing pattern, an extra diffusion mixing ( = + D log 3.125 mix 0.250 ) should be considered, but the normal core overshooting fov must be fixed as zero in the best-fitting model. Such ultraweak mixing beyond the convective core corresponds to a fast rotation that is about 20–30 times the asteroseismic suggested rotation Ωrot;0.2 μHz, if it is thought of as shear mixing induced completely by differential rotation. Unified Astronomy Thesaurus concepts: Asteroseismology (73); Stellar interiors (1606); Stellar oscillations (1617); Stellar structures (1631); Fundamental parameters of stars (555); Stellar rotation (1629); Stellar properties (1624); B stars (128)

中文翻译:

缓慢脉动 B 星 KIC 8324482 的星震分析:超弱元素混合超出中央对流核心

星震学是探测恒星内部结构、确定恒星演化状态和基本参数的有力工具。慢脉动 B (SPB) 星的振荡光谱显示出几乎一致的周期跨度,其模式对中心对流核心以外的 μ 梯度壳结构敏感,因此可用于有效描述它们的形状并约束对流核心. SPB 星 KIC8324482 被开普勒以长节奏模式观测了超过 1470 天。Zhangetal 从振荡谱中提取的 14 种连接偶极模式发现了几乎等距的周期间隔模式。在目前的工作中,我们使用 χ2 匹配方法深入分析它们并确定它们的 χ2 最小化模型(CMM)。基于那些计算出的 CMM,我们发现 KIC8324482 是一个年轻的 (= + t 20.96 age 1.28 3.85 Myr)、贫金属 (= + Fe H 0.6.9 0.115 0.176 [ ] dex) 和中等质量的 (= MM 6.07075 0.2)对流核心= + MM 1.338 CC 0.091 0.057  质量和= + RR 0.5175 CC 0.0103 0.0048  半径和表面旋转速度= + V 2.61 km s eq 0.1110 的恒星。 = + X 0.5046 C 0.0074。星震分析表明KIC8324482中g模式的“传播时间”为L = 0 + 276.85 0.47 1.26 μHz。为了与观察到的周期间隔模式很好地匹配,应该考虑额外的扩散混合 (= + D log 3.125 mix 0.250 ),但在最佳拟合模型中,正常的核心超调 fov 必须固定为零。这种超出对流核心的超弱混合对应于一个快速旋转,大约是星震建议旋转 Ωrot;0.2 μHz 的 20-30 倍,如果它被认为是完全由差动旋转引起的剪切混合。统一天文学词库概念:Asterseismology (73);恒星内部(1606);恒星振荡(1617);恒星结构(1631);恒星的基本参数(555);恒星自转(1629);恒星属性(1624);B 星 (128) 恒星属性(1624);B 星 (128) 恒星属性(1624);B 星 (128)
更新日期:2020-08-11
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