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No Sun-like dynamo on the active star zeta Andromedae from starspot asymmetry

机译：星点不对称导致活动恒星zeta Andromedae上没有类似太阳的发电机

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摘要

Sunspots are cool areas caused by strong surface magnetic fields that inhibit convection(1,2). Moreover, strong magnetic fields can alter the average atmospheric structure(3), degrading our ability to measure stellar masses and ages. Stars that are more active than the Sun have more and stronger dark spots than does the Sun, including on the rotational pole(4). Doppler imaging, which has so far produced the most detailed images of surface structures on other stars, cannot always distinguish the hemisphere in which the starspots are located, especially in the equatorial region and if the data quality is not optimal(5). This leads to problems in investigating the north-south distribution of starspot active latitudes (those latitudes with more starspot activity); this distribution is a crucial constraint of dynamo theory. Polar spots, whose existence is inferred from Doppler tomography, could plausibly be observational artefacts(6). Here we report imaging of the old, magnetically active star zeta Andromedae using long-baseline infrared interferometry. In our data, a dark polar spot is seen in each of two observation epochs, whereas lower-latitude spot structures in both hemispheres do not persist between observations, revealing global starspot asymmetries. The north-south symmetry of active latitudes observed on the Sun(7) is absent on zeta And, which hosts global spot patterns that cannot be produced by solar-type dynamos(8).
机译：太阳黑子是由强表面磁场引起的冷区域，该磁场会抑制对流（1,2）。此外，强磁场会改变平均大气结构（3），从而降低了我们测量恒星质量和年龄的能力。比太阳活跃的恒星，包括旋转极在内，其暗点也比太阳强得多（4）。到目前为止，多普勒成像技术已经在其他恒星上产生了最详细的表面结构图像，但不能总是分辨出星点所在的半球，特别是在赤道区域，并且如果数据质量不是最佳的（5）。这导致在调查星点活动纬度（那些具有更多星点活动的纬度）的南北分布方面存在问题；这种分布是发电机理论的关键约束。从多普勒断层扫描推断存在的极点可能是观测伪像（6）。在这里，我们报告了使用长基线红外干涉仪对旧的，具有磁性的恒星zeta Andromedae的成像。在我们的数据中，在两个观测纪元中的每个观测纪元都出现了一个暗极点，而两个半球的低纬度点结构在两次观测之间并没有持续存在，从而揭示了整体的星点不对称。 Zeta And上没有观测到在太阳上观测到的活动纬度的南北对称（7），它具有无法由太阳型发电机产生的全局斑点模式（8）。

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  • 来源
    《Nature》 |2016年第7602期|217-220|共4页
  • 作者

    Roettenbacher R. M.; Monnier J. D.; Korhonen H.; Aarnio A. N.; Baron F.; Che X.; Harmon R. O.; Kovari Zs.; Kraus S.; Schaefer G. H.; Torres G.; Zhao M.; ten Brummelaar T. A.; Sturmann J.; Sturmann L.;

  • 作者单位

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA;

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA;

    Univ Turku, Finnish Ctr Astron ESO FINCA, FI-21500 Piikkio, Finland|Univ Copenhagen, Niels Bohr Inst, Dark Cosmol Ctr, Juliane Maries Vej 30, DK-2100 Copenhagen O, Denmark;

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA;

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA|Georgia State Univ, Dept Phys & Astron, Atlanta, GA 30303 USA;

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA;

    Ohio Wesleyan Univ, Dept Phys & Astron, Delaware, OH 48103 USA;

    Hungarian Acad Sci, Konkoly Observ, Res Ctr Astron & Earth Sci, Konkoly Thege Miklos Ut 15-17, H-1121 Budapest, Hungary;

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA|Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England;

    Georgia State Univ, Ctr High Angular Resolut Astron, Mt Wilson, CA 91023 USA;

    Harvard Smithsonian Ctr Astrophys, 60 Garden St, Cambridge, MA 02138 USA;

    Univ Michigan, Dept Astron, Ann Arbor, MI 48109 USA|Penn State Univ, Dept Astron & Astrophys, State Coll, PA 16802 USA;

    Georgia State Univ, Ctr High Angular Resolut Astron, Mt Wilson, CA 91023 USA;

    Georgia State Univ, Ctr High Angular Resolut Astron, Mt Wilson, CA 91023 USA;

    Georgia State Univ, Ctr High Angular Resolut Astron, Mt Wilson, CA 91023 USA;

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