Poster Open Access
Coffaro M.; Stelzer B.; Orlando S.; Hall J.; Metcalfe T.S.; Wolter U.; Mittag M.; Sanz-Forcada J.; Ducci L.
Epsilon Eri is a young solar-like star with a ~3 yr X-ray activity cycle, detected by us for the first time in a dedicated XMM-Newton long-term monitoring campaign. The magnetic structures on the Sun are intimately linked to the 11-yr activity cycle and they were spatially and temporally resolved throughout the solar cycle. However, for other stars these structures can not be spatially resolved with present-day X-ray instruments. We have, thus, developed a new technique which allows us to reproduce the stellar X-ray variability in terms of time-variations in the coverage of the corona with the same kind of magnetic structures observed on the Sun: active regions (ARs), cores of active regions (COs) and flares (FLs). This poster presents this new method and the results we obtained for the case of Epsilon Eri. Our approach is to simulate a grid of emission measure distributions (EMDs) derived from the analysis of regions observed in the solar corona to artificially reproduce a solar-like corona with the physical characteristics of Epsilon Eri. The three magnetic structures are allowed to contribute to the total coronal EMD with varying area coverage fraction. Thus, from a comparison between these pseudo-solar EMDs and the observations of Epsilon Eri, we are able to associate to each state of the X-ray activity cycle of Epsilon Eri the percentage of ARs, COs and FLs on the corona of the star. The observed amplitude of the X-ray luminosity in the cycle of Epsilon Eri is much smaller than on the Sun. Our analysis provides a physical explanation for this: the simulated EMDs indicate that in all phases of the X-ray cycle a large portion of the corona of Epsilon Eri is covered by active structures. Therefore, there is little space for adding further magnetic structures in the cycle maximum. In the future, this method will be applied to other stars providing an important contribution to better understand the solar-stellar corona connection.
Coffaro et al. 2020; A&A, 636, A49; doi 10.1051/0004-6361/201936479