Title: Detection of solar-like oscillations in the red giant star epsilon Ophiuchi by MOST spacebased photometry
Authors: Barban, C ×
Matthews, J. M
De Ridder, Joris
Baudin, F
Kuschnig, R
Mazumdar, A
Samadi, R
Guenther, D. B
Moffat, A. F. J
Rucinski, S. M
Sasselov, D
Walker, G. A. H
Weiss, W. W #
Issue Date: Jun-2007
Publisher: Edp sciences s a
Series Title: Astronomy & astrophysics vol:468 issue:3 pages:1033-1038
Abstract: Context: Solar-like oscillations have been discovered in a few red giants, including ɛ Oph, through spectroscopy. Acoustic modes around 60 μHz 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 ɛ 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) μHz. 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.
ISSN: 0004-6361
Publication status: published
KU Leuven publication type: IT
Appears in Collections:Institute of Astronomy
× corresponding author
# (joint) last author

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