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arXiv 2410.06142astro-ph.SR
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HD 4915中不存在蒙德极小期阶段

No Maunder Minimum phase in HD 4915

M. Flores-Trivigno, A. P. Buccino, E. González, P. D. Colombo, C. González, M. Jaque-Arancibia, R. V. Ibáñez Bustos, C. Saffe, P. Miquelarena, J. Alacoria, A. Collado

AI总结:

本研究针对类太阳恒星HD 4915是否处于蒙德极小期的问题,通过分析HARPS与HIRES的380余条光谱,排除了其进入蒙德极小期的可能,提出其活动模式由4.8年短周期受长周期调制的多重周期主导。

摘要:

由发电机机制维持的太阳长期磁活动及其周期性行为,对天体物理学而言仍是具有挑战性的课题。其中,1645年至1715年间发生了一次非典型事件:当时太阳活动显著减弱,太阳黑子数量大幅减少,但太阳周期在此期间的具体变化仍不明确。在冷星中发现更长的活动极小期,或许能揭示太阳-恒星发电机长期行为所涉及复杂机制的本质。我们的研究目标是,探究G5V型类太阳恒星HD 4915是否可作为真正的蒙德极小期(以下简称MM)候选体;此前一项基于HIRES数据的研究显示,该恒星呈现出显著的色球活动模式。我们分析了2003年至2022年间使用HARPS和HIRES光谱仪获取的380余条光谱,通过威尔逊山活动指数与巴耳末H$_α$活动指数,对HD 4915的活动特征开展了详细搜寻,这项工作借助GLS周期图完成。新的HARPS数据显示,HD 4915的色球活动并未减弱。实际上,在持续三年的宽极小期后,活动水平回升至该阶段之前的活动水平,表明它并未进入MM阶段。HD 4915最初被认为可能处于MM初期阶段的独特活动行为,在新增的HARPS数据支持下,我们排除了该恒星处于MM的可能。我们的分析表明,HD 4915的复杂活动模式可能由多重活动周期主导:一个4.8年的较短周期受到一个潜在更长周期的调制。开展更多拥有长期记录与合适采样频率的活动巡天,对于准确识别处于磁大极小期的恒星至关重要。

英文摘要:

The long-term solar magnetic activity and its cyclical behaviour, which is maintained by a dynamo mechanism, are both still challenging for the astrophysics. In particular, an atypical event occurred between 1645 and 1715 when the solar activity was remarkably decreased and the number of sunspots got extremely reduced. However, it is still unclear what happened to the solar cycle. The discovery of longer activity minima in cool stars may shed light on the nature of the complex mechanisms involved in the long-term behaviour of the solar-stellar dynamo. Our aim is to explore if the G5V solar-like star HD 4915, which showed a striking chromospheric activity pattern in a previous study performed with HIRES data, could be considered a bona fide Maunder Minimum (hereafter MM) candidate. We have analyzed over 380 spectra acquired between 2003 and 2022 using HARPS and HIRES spectrographs. We carried out a detailed search of activity signatures in HD 4915 by using the Mount Wilson and the Balmer H$_α$ activity indexes. This task was performed by means of the GLS periodogram. The new HARPS data show that the chromospheric activity of HD 4915 is not decreasing. In fact, the rise of the activity after the broad minimum in three years gets to the level of activity before that phase, suggesting that it is not entering into a MM phase. HD 4915 shows a distinctive activity behaviour initially attributed to a possible and incipient MM phase. The additional HARPS data allow us to discard a MM in the star. Our analysis shows that the complex activity pattern of HD 4915 could be ruled by a multiple activity cycle, being a shorter cycle of 4.8-yr modulated by a potential longer one. More activity surveys with extensive records and suitable cadence are crucial for accurate identification of stars in Magnetic Grand Minima.

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