학술논문
Expanding the frontiers of cool-dwarf asteroseismology with ESPRESSO. Detection of solar-like oscillations in the K5 dwarf $\epsilon$ Indi
Document Type
Working Paper
Author
Campante, T. L.; Kjeldsen, H.; Li, Y.; Lund, M. N.; Silva, A. M.; Corsaro, E.; da Silva, J. Gomes; Martins, J. H. C.; Adibekyan, V.; Silva, T. Azevedo; Bedding, T. R.; Bossini, D.; Buzasi, D. L.; Chaplin, W. J.; Costa, R. R.; Cunha, M. S.; Cristo, E.; Faria, J. P.; García, R. A.; Huber, D.; Lundkvist, M. S.; Metcalfe, T. S.; Monteiro, M. J. P. F. G.; Neitzel, A. W.; Nielsen, M. B.; Poretti, E.; Santos, N. C.; Sousa, S. G.
Source
A&A, 683, L16 (2024)
Subject
Language
Abstract
Fuelled by space photometry, asteroseismology is vastly benefitting the study of cool main-sequence stars, which exhibit convection-driven solar-like oscillations. Even so, the tiny oscillation amplitudes in K dwarfs continue to pose a challenge to space-based asteroseismology. A viable alternative is offered by the lower stellar noise over the oscillation timescales in Doppler observations. In this letter we present the definite detection of solar-like oscillations in the bright K5 dwarf $\epsilon$ Indi based on time-intensive observations collected with the ESPRESSO spectrograph at the VLT, thus making it the coolest seismic dwarf ever observed. We measured the frequencies of a total of 19 modes of degree $\ell=0$--2 along with $\nu_{\rm max}=5305\pm176\:{\rm \mu Hz}$ and $\Delta\nu=201.25\pm0.16\:{\rm \mu Hz}$. The peak amplitude of radial modes is $2.6\pm0.5\:{\rm cm\,s^{-1}}$, or a mere ${\sim} 14\%$ of the solar value. Measured mode amplitudes are ${\sim} 2$ times lower than predicted from a nominal $L/M$ scaling relation and favour a scaling closer to $(L/M)^{1.5}$ below ${\sim} 5500\:{\rm K}$, carrying important implications for our understanding of the coupling efficiency between pulsations and near-surface convection in K dwarfs. This detection conclusively shows that precise asteroseismology of cool dwarfs is possible down to at least the mid-K regime using next-generation spectrographs on large-aperture telescopes, effectively opening up a new domain in observational asteroseismology.
Comment: Accepted for publication in Astronomy & Astrophysics Letters
Comment: Accepted for publication in Astronomy & Astrophysics Letters