March 24, 2015

Stellar Seismology Results

Solar-type pulsators: a long-expected extension of the Solar experience

Corot reveals a magnetic activity cycle in a Sun-like star, using modulation of the seismic parameters

Solar-like oscillations in the star HD49933
Solar-like oscillations in the star HD49933.

Solar-like oscillations in the star HD49933, have been analyzed for signatures of stellar magnetic activity. Measurements of global changes in the oscillation frequencies and mode amplitudes reveal a modulation of at least 120 days, with the minimum frequency shift corresponding to maximum amplitude as in the Sun. This is interpreted as evidence of a stellar magnetic activity cycle taking place beneath the surface of HD49933.

Associated publications


Intermediate mass stars: where rotation and transport of chemical species hold the scene

HD50844: a new look at delta SCuti stars from Corot space photometry

Amplitude spectrum of the rotational variable HD 292790For comparison purposes, the top panel shows the amplitude spectrum of the rotational variable HD 292790. This star has been observed by Corot simultaneously to HD 50844. The amplitude spectra of HD 50844 shown in the other panels indicate the extreme richness of the pulsational spectrum of this d Sct star: up to 1000 peaks are needed to make the residual spectrum of HD 50844 comparable to the original one of HD 292790.

Associated publications


Hot and massive stars: processing new nucleus and enriching the universe

Corot detects the deviations from a uniform period spacing of gravity modes in a massive star.

This pseudo sinusoidal oscillation of the period spacing of gravity modes in a 7 solar mass star indicates an extension of the convective core of at least 0.2 Hp
This pseudo sinusoidal oscillation of the period spacing of gravity modes in a 7 solar mass star indicates an extension of the convective core of at least 0.2 Hp.

Associated publications


Red giants: The future of our Sun, the history of our Galaxy

Non-radial oscillation modes with long lifetimes in giant stars

Power density spectrum of the red giant candidate Corot-101034881
Power density spectrum of the red giant candidate Corot-101034881 showing a frequency pattern with a regular spacing. This spacing is predicted by the theoretical asymptotic relation for high-order and low-degree oscillations. Using the auto-correlation function of the power spectrum, we derive the large separation to be 4.8 µHz. This value is consistent with what is expected for red giants from scaling laws.

Associated publications


Seismology of rapidly rotating stars (or Very evolved objects?)

Pulsation modes in rapidly rotating stellar models based on the self-consistent field method

Comparison of a pulsation mode
Comparison of a pulsation mode calculated using finite differences (left), a spectral method (centre), and polynomial splines (right) to discretise the equations in the radial direction. These and other similar plots show a meridional cross-section of the Eulerian pressure perturbation divided by the square root of the background density profile so as to bring out near surface regions. The difference on the frequencies is less than 0:1 µHz.

Associated publications


Evolved objects: RR Lyrae, Long period variables and subdwarfs

The long continuous observations of Corot traces the periodic modulation of the amplitude of the pulsation of the RR Lyrae star V 1127 Aquilae.

The amplitude modulation or Blashko effect is not yet understood. This light curve covers 5 cycles, showing a very rich frequency content with non linear behavior and non radial modes.
The amplitude modulation or Blashko effect is not yet understood. This light curve covers 5 cycles, showing a very rich frequency content with non linear behavior and non radial modes.

Associated publications