Asteroseismology of $\mathsf{\alpha}$ Centauri A

Abstract

Context. Asteroseismology provides a unique tool for studying stellar interiors. Recently p modes have been detected on the bright solar-like star α Cen A thanks to high-precision radial-velocity measurements. However, a better characterisation of these p modes is clearly needed to constrain theoretical models. Aims. We observed α Cen A during five nights using the HARPS spectrograph in order to improve our knowledge of the seismic properties of this star. Methods. We performed high-precision radial-velocity sequences and computed the acoustic spectrum of α Cen A. Results. We identify 34 p modes with angular degree l = 0−3 in the frequency range 1.8-2.9 mHz and amplitude range 13-48 cm s −1 , in agreement with previous seismic studies. We find an enhancement of the frequency scatter with the angular degree l that indicates, considering the high inclination axis of α Cen A, rotational splitting and explains the low values of previously suggested mode lifetimes. We also derive new values for the small separations that take the effect of rotational splitting into account. Conclusions. Our seismic study of α Cen A leads to a list of now well-identified p-mode frequencies and shows the importance of taking the rotation into account in order to properly characterise the p modes even in quite short campaigns.

Planetary detection limits taking into account stellar noise

“…Therefore, activity noise is not fully included. Sousa et al (2008); (b) Bedding et al (2007); (c) Bazot et al (2007); (d) Bouchy et al (2005); (e) Teixeira et al (2009). ST is for spectral type and T exp for exposure time.…”

“…It has been shown that these anomalies are due to a problem in the guiding engine of the telescope, resulting in poor guiding precision (e.g. Teixeira et al 2009;Bedding et al 2007;Bazot et al 2007;Carrier & Eggenberger 2006). The data for α Cen B, taken in 2009, does not exhibit these peaks because of the corrections made to the guiding software.…”

Differential Rotation in Sun-like Stars from Surface Variability and Asteroseismology

“…Therefore, for a slowly rotating Sun-like star we may make the approximation that 4) where Ω/2π is equivalent to the rotational splitting which is often denoted by δν. In most studies this is what is used when fitting oscillation spectra in order to measure the mean rotation of stars (Bazot et al 2007, Appourchaux et al 2008, Lund et al 2014a). …”

Keplerobservations of the asteroseismic binary HD 176465

“…However, few binary systems have solar-like oscillations detected in both components. Three systems exist in which the two components have been observed separately: α Cen A (e.g Bouchy & Carrier 2002;Bedding et al 2004;Fletcher et al 2006;Bazot et al 2007), and B (Carrier & Bourban 2003;Kjeldsen et al 2005), 16 Cyg A and B (KIC 12069424 and KIC 12069449;Metcalfe et al 2012Metcalfe et al , 2015Davies et al 2015), and HD 176071 (KIC 9139151 and KIC 9139163;Appourchaux et al 2012). Additionally, oscillations in both components of HD 177412 (HIP 93511) have been measured while observed as a single Kepler target, KIC 7510397 (Appourchaux et al 2015).…”