HD38858: a solar type star with a ~10.8 yr activity cycle.

M. FLORES; J. F. GONZÁLEZ; M. JAQUE ARANCIBIA; C. SAFFE; A. BUCCINO; F. M. LÓPEZ; R. V. IBAÑEZ BUSTOS; P. MIQUELARENA

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2018

0004-6361

Context. The detection of chromospheric activity cycles insolar-analogue and twin stars, can be used to put in context the solarcycle. However, there is a relatively low percentage of these stars withactivity cycles detected. It is well known that the cores of Ca IIH&K lines are modulated by stellar activity. The behaviour of Balmerand other optical lines with stellar activity is not yet completelyunderstood. Aims. To search for Ca II H&K, Balmer and Fe II linevariations modulated by the stellar activity. In particular, we apply anovel strategy to detect possible shape variations in the H{alpha}line. Methods. We analyse activity signatures in HD 38858 by using HARPSand CASLEO spectra obtained between 2003 and 2017. We calculate theMount Wilson index (S$_{MW}$), log($mathrm{R}´_mathrm{HK}$) and thestatistical moments of Ca II H&K, Balmer and other optical lines. Wesearch for periodicities by using the generalized Lomb-Scargleperiodogram. Results. We detect a long-term activity cycle of 10.8 yr inCa II H&K and H{alpha}, being HD 38858 one of the most similarstars to the Sun for which a cycle has been detected. In contrast, thiscycle is marginally detected in the Fe II lines. Also, we detect anoticeable radial velocity variation, which seems to be produced bystellar activity. Conclusions. HD 38858 is the second solar-analoguestar where we find a clear activity cycle which is replicated by Balmerlines. Spectral indexes based on the shape of H{alpha} seems to be morerealiable than the fluxes in the same line to detect activityvariations. On the other hand, the cyclic modulation detected givesplace to a radial velocity variation, previously associated to asuper-Earth planet. Finally, due to the similarity of HD 38858 with theSun, we recommend to continue monitoring this star.