ιHorologi, the first coronal activity cycle in a young solar-like star

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  • J. Sanz-Forcada, Departamento de Astrofísica, Centro de Astrobiología (CSIC-INTA
  • ,
  • B. Stelzer, INAF - Osservatorio Astronomico di Palermo G. S. Vaiana, Piazza del Parlamento 1, 90134, Palermo, Italy stelzer@oapa.inaf.it
  • ,
  • T. S. Metcalfe
Context. The shortest chromospheric (Ca ii H&K) activity cycle (1.6 yr) has been recently discovered in the young (~600 Myr) solar-like star ι Hor. Coronal X-ray activity cycles have only been discovered in a few stars other than the Sun, all of them with an older age and a lower activity level than ι Hor. Aims: We intended to find the X-ray coronal counterpart of the chromospheric cycle for ι Hor. This represents the first X-ray cycle observed in an active star, as well as the paradigm of the first coronal cycles in the life of a solar-like star. Methods: We monitored ι Hor with XMM-Newton observations spanning almost two years. The spectra of each observation are fit with two-temperature coronal models to study the long-term variability of the star. Results: We find a cyclic behavior in X-rays very similar to the contemporaneous chromospheric cycle. The continuous chromospheric monitoring for more than three cycle lengths shows a trend toward decreasing amplitude, apparently modulated by a longer term trend. The second cycle is disrupted prior to reaching its maximum, followed by a brief episode of chaotic variability before the cyclic behavior resumes, only to be disrupted again after slightly more than one cycle. Conclusions: We confirm the presence of an activity cycle of ~1.6 yr in ι Hor both in X-rays and Ca ii H&K. It is likely subject to the modulation of a longer, not yet constrained second cycle. The 1.6 yr cycle is the shortest coronal one observed to date, and ι Hor represents the most active star for which a coronal activity cycle has been found. This cycle is probably representative of the first coronal cycles in the life of a solar-like star, at the age when life started on Earth. Table 2 is available in electronic form at http://www.aanda.org
OriginalsprogEngelsk
ArtikelnummerL6
TidsskriftAstronomy & Astrophysics
Vol/bind553
Antal sider5
ISSN0004-6361
DOI
StatusUdgivet - 2013

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