Detection of solar-like oscillations in the red giant star ε Ophiuchi by MOST spacebased photometry - Université Paris Cité Accéder directement au contenu
Article Dans Une Revue Astronomy and Astrophysics - A&A Année : 2007

Detection of solar-like oscillations in the red giant star ε Ophiuchi by MOST spacebased photometry

Résumé

Context: Solar-like oscillations have been discovered in a few red giants, including ε Oph, through spectroscopy. Acoustic modes around 60 muHz were clearly seen in this star, but daily aliasing of the groundbased data made it impossible to unambiguously isolate the p-mode frequencies in the eigenspectrum, and hence the correct value of the large spacing, to asteroseismically constrain the mass of this pulsating star.
Aims: We obtained about 28 days of contiguous high-precision photometry of ε Oph in May-June 2005 with the MOST (Microvariability & Oscillations of STars) satellite. The thorough time sampling removes the ambiguity of the frequency identifications based on the groundbased discovery data.
Methods: We identify equidistant peaks in the Fourier spectrum of the MOST photometry in the range where the p-modes were seen spectroscopically. Those peaks are searched by autocorrelation of the power spectrum to estimate the value of the large separation in the p-mode eigenspectrum. Having isolated the oscillation modes, we determine their mode parameters (frequency, amplitude and line width) by fitting the distribution of peaks to Lorentzian profiles.
Results: The clear series of equidistant peaks in the power spectrum, with amplitudes from about 30 to 130 ppm, are consistent with radial modes spaced by a mean value of ( 5.3 ± 0.1) muHz. This large separation matches one of the two possibilities allowed by the groundbased observations thus constraining the stellar models to a much greater extent than previously possible. The line widths and Lorentzian fits indicate a rather short average mode lifetime: (2.7+0.6-0.8}) days.
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hal-03801078 , version 1 (13-10-2022)

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Caroline Barban, Jaymie M. Matthews, Joris de Ridder, Frederic Baudin, R. Kuschnig, et al.. Detection of solar-like oscillations in the red giant star ε Ophiuchi by MOST spacebased photometry. Astronomy and Astrophysics - A&A, 2007, 468, pp.1033-1038. ⟨10.1051/0004-6361:20066716⟩. ⟨hal-03801078⟩
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