First long-term activity study of AU Microscopii: a possible chromospheric cycle

IBAÑEZ BUSTOS, R V; BUCCINO, A P; FLORES, M; MARTINEZ, C I; MAIZEL, D; MESSINA, SERGIO; MAUAS, P J D

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2018

0035-8711

M stars are ideal targets to search for Earth-like planets. However, they usually have high levels of magnetic activity, which could affect their habitabilityand make difficult the detection of exoplanets orbiting around them. Unfortunately, long-term variability of dM stars has not been extensively studied,due to their low intrinsic brightness. For this reason, in 1999 we started theHKα project, which systematically observes the spectra of a large numberof stars, in particular dM stars, at the Complejo Astron´omico El Leoncito(CASLEO). In this work, we study the long-term activity of the young activedM1 star AU Microscopii. We analyze the Mount Wilson index S derived fromCASLEO spectra obtained between 2004 and 2016, which we complement withthe S-index derived from HARPS, FEROS and UVES public spectra. We alsoanalyze the simultaneous photometric counterpart provided by the ASAS public database for this star between 2000 and 2009, and our own photometry.In both totally independent time series, we detect a possible activity cycleof period ∼ 5 years. We also derived a precise rotation period for this starProt = 4.85 days, consistent with the literature. This activity cycle reflectsthat an αΩ dynamo could be operating in this star.