Solar-like oscillations and magnetic activity of the slow rotator EK Eri

Abstract

We aim to understand the interplay between non-radial oscillations and stellar magnetic activity and test the feasibility of doing asteroseismology of magnetically active stars. We analyze 30 years of photometric time-series data, 3 years of HARPS radial velocity monitoring, and 3 nights of high-cadence HARPS asteroseismic data. We construct a high-S/N HARPS spectrum that we use to determine atmospheric parameters and chemical composition. Spectra observed at different rotation phases are analyzed to search for signs of temperature or abundance variations. An upper limit on the projected rotational velocity is derived from very high-resolution CES spectra. We detect oscillations in EK Eri with a frequency of the maximum power of nu_max = 320+/-32 muHz, and we derive a peak amplitude per radial mode of ~0.15 m/s, which is a factor of ~3 lower than expected. We suggest that the magnetic field may act to suppress low-degree modes. Individual frequencies can not be extracted from the available data. We derive accurate atmospheric parameters, refining our previous analysis. We confirm that the main light variation is due to cool spots, but that other contributions may need to be taken into account. We suggest that the rotation period is twice the photometric period, i.e., P_rot = 2 P_phot = 617.6 d. We conclude from our derived parameters that v sin i < 0.40 km/s. We also link the time series of direct magnetic field measurements available in the literature to our newly derived photometric ephemeris.

11 pages, 10 figures. Accepted by A&A

References in corpus (16)

• ADIPLS -- the Aarhus adiabatic oscillation package
• The HARPS search for southern extra-solar planets. X. A m sin i = 11 Mearth planet around the nearby spotted M dwarf GJ 674
• TW Hydrae: evidence of stellar spots instead of a Hot Jupiter
• Search for exoplanets with the radial-velocity technique: quantitative diagnostics of stellar activity
• Radius determination of solar-type stars using asteroseismology: What to expect from the Kepler mission
• Characteristics of solar-like oscillations in red giants observed in the CoRoT exoplanet field
• A multi-site campaign to measure solar-like oscillations in Procyon. I. Observations, Data Reduction and Slow Variations
• The amplitude of solar oscillations using stellar techniques
• Determination of stellar radii from asteroseismic Data
• Oscillating K giants with the WIRE satellite: determination of their asteroseismic masses
• A spectroscopic study of southern (candidate) gamma Doradus stars. II. Detailed abundance analysis and fundamental parameters
• Discovery of a weak magnetic field in the photosphere of the single giant Pollux
• Bisectors of the cross-correlation function applied to stellar spectra. Discriminating stellar activity, oscillations and planets
• EK Eridani: the tip of the iceberg of giants which have evolved from magnetic Ap stars
• Pulsations in the atmosphere of the roAp star HD 24712 II. Theoretical models
• The Discovery of Stellar Oscillations in the Planet Hosting Giant Star Beta Geminorum

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