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Abstract
Context: Red giants are evolved stars that exhibit solar-like oscillations. Although a multitude of stars have been observed with space
telescopes, only a handful of red giant stars were targets of spectroscopic asteroseismic observing projects.
Aims: We search for solar-like oscillations in the two bright red giant stars γ Psc and θ1 Tau from a time series of ground-based
spectroscopy and determine the frequency of the excess of oscillation power νmax and the mean large frequency separation Δν for both
stars. Seismic constraints on the stellar mass and radius will provide robust input for stellar modelling.
Methods: The radial velocities of γ Psc and θ1 Tau were monitored for 120 and 190 days, respectively. Nearly 9000 spectra were
obtained. To reach accurate radial velocities, we used simultaneous thorium-argon and iodine-cell calibration of our optical spectra.
In addition to the spectroscopy, we acquired interferometric observations of γ Psc for an independent estimate of the radius. We also
analysed 22 days of observations of θ1 Tau with the MOST satellite.
Results: The frequency analysis of the radial velocity data of γ Psc revealed an excess of oscillation power around 32 μHz and a
large frequency separation of 4.1 ± 0.1 μHz. θ1 Tau exhibits oscillation power around 90 μHz, with a large frequency separation
of 6.9 ± 0.2 μHz. Scaling relations indicate that γ Psc is a star of about 1 M⊙ and 10 R⊙. The object θ1 Tau appears to be a massive
star of about 2.7 M⊙ and 10 R⊙. The radial velocities of both stars were found to be modulated on timescales much longer than the
oscillation periods.
Conclusions: The estimated radii from seismology are in agreement with interferometric observations and also with estimates based
on photometric data. While the mass of θ1 Tau is in agreement with results from dynamical parallaxes, we find a lower mass for γ Psc
than is found in the literature. The long periodic variability agrees with the expected timescales of rotational modulation.
Original language | English |
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Article number | A138 |
Number of pages | 15 |
Journal | Astronomy and Astrophysics |
Volume | 573 |
DOIs | |
Publication status | Published - 15 Jan 2015 |
Keywords
- astro-ph.SR
- asteroseismology
- stars: rotation
- techniques: interferometric
- techniques: spectroscopic
- stars: general
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Dive into the research topics of 'Detection of solar-like oscillations in the bright red giant stars γ Piscium and θ1 Tauri from a 190-day high-precision spectroscopic multi-site campaign'. Together they form a unique fingerprint.Projects
- 1 Finished
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Sounding the Stars---The Birmingham and Queen Mary Seismology Programme
Elsworth, Y., Chaplin, B. & Miglio, A.
SCIENCE & TECHNOLOGY FACILITIES COUNCIL
1/04/12 → 31/03/15
Project: Research Councils