Bibcode
Blomme, R.; Mahy, L.; Catala, C.; Cuypers, J.; Gosset, E.; Godart, M.; Montalban, J.; Ventura, P.; Rauw, G.; Morel, T.; Degroote, P.; Aerts, C.; Noels, A.; Michel, E.; Baudin, F.; Baglin, A.; Auvergne, M.; Samadi, R.
Referencia bibliográfica
Astronomy and Astrophysics, Volume 533, id.A4, 13 pp.
Fecha de publicación:
9
2011
Revista
Número de citas
95
Número de citas referidas
80
Descripción
Context. The detection of pulsational frequencies in stellar photometry
is required as input for asteroseismological modelling. The second short
run (SRa02) of the CoRoT mission has provided photometric data of
unprecedented quality and time-coverage for a number of O-type stars.
Aims: We analyse the CoRoT data corresponding to three hot O-type
stars, describing the properties of their light curves and search for
pulsational frequencies, which we then compare to theoretical model
predictions. Methods: We determine the amplitude spectrum of the
data, using the Lomb-Scargle and a multifrequency HMM-like technique.
Frequencies are extracted by prewhitening, and their significance is
evaluated under the assumption that the light curve is dominated by red
noise. We search for harmonics, linear combinations, and regular
spacings among these frequencies. We use simulations with the same time
sampling as the data as a powerful tool to judge the significance of our
results. From the theoretical point of view, we use the MAD
non-adiabatic pulsation code to determine the expected frequencies of
excited modes. Results: A substantial number of frequencies is
listed, but none can be convincingly identified as being connected to
pulsations. The amplitude spectrum is dominated by red noise.
Theoretical modelling shows that all three O-type stars can have excited
modes, but the relation between the theoretical frequencies and the
observed spectrum is not obvious. Conclusions: The dominant red
noise component in the hot O-type stars studied here clearly points to a
different origin than the pulsations seen in cooler O stars. The
physical cause of this red noise is unclear, but we speculate on the
possibility of sub-surface convection, granulation, or stellar wind
inhomogeneities being responsible.
The CoRoT space mission was developed and is operated by the French
space agency CNES, with participation of ESA's RSSD and Science
Programmes, Austria, Belgium, Brazil, Germany and Spain.Tables 2-4 are
available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr
(130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/533/A4