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标题：Multi-wavelength variability of the young solar analog ι Horologii
其他标题：X-ray cycle, star spots, flares, and UV emission
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作者：J. Sanz-Forcada ; B. Stelzer ; M. Coffaro 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2019
卷号：631
页码：1-14
DOI：10.1051/0004-6361/201935703
语种：English
出版社：EDP Sciences
摘要：Context.Chromospheric activity cycles are common in late-type stars; however, only a handful of coronal activity cycles have been discovered.ιHor is the most active and youngest star with known coronal cycles. It is also a young solar analog, and we are likely facing the earliest cycles in the evolution of solar-like stars, at an age (~600 Myr) when life appeared on Earth.Aims.Our aim is to confirm the ~1.6 yr coronal cycle and characterize its stability over time. We use X-ray observations ofιHor to study the corona of a star representing the solar past through variability, thermal structure, and coronal abundances.Methods.We analyzed multi-wavelength observations ofιHor usingXMM-Newton, TESS, and HST data. We monitoredιHor throughout almost seven years in X-rays and in two UV bands. The summed RGS and STIS spectra were used for a detailed thermal structure model, and the determination of coronal abundances. We studied rotation and flares in the TESS light curve.Results.We find a stable coronal cycle along four complete periods, more than covered in the Sun. There is no evidence for a second longer X-ray cycle. Coronal abundances are consistent with photospheric values, discarding any effects related to the first ionization potential. From the TESS light curve we derived the first photometric measurement of the rotation period (8.2 d). No flares were detected in the TESS light curve ofιHor. We estimate the probability of having detected zero flares with TESS to be ~2%.Conclusions.We corroborate the presence of an activity cycle of ~1.6 yr inιHor in X-rays, more regular than its Ca IIH&K counterpart. A decoupling of the activity between the northern and southern hemispheres of the star might explain the disagreement. The inclination of the system would result in an irregular behavior in the chromospheric indicators. The more extended coronal material would be less sensitive to this effect.
关键词：Key wordsenstars: activitystars: coronaestars: chromospheresstars: abundancesplanetary systemsstars: individual: ι Hor