Massive variable main sequence stars have frequency spectra dominated by acoustic modes excited by the κ mechanism at work in layers where partial ionization of iron group elements produce a peak in opacity.
In addition the most advanced of these stars present mixed modes i.e. modes with a g-character in deep layers and p-character in the envelope.
Hydrogen burning takes place in a convective core surrounded by a region of varying chemical composition and an envelope mostly radiative except for tiny convective layers related to partial ionization of helium and/or iron group elements.
As in lower mass stars the extent of the fully or partially mixed region located just above the convective core (extra-mixed zone) is one of the main uncertainties affecting theoretical modeling.

β Cephei stars: Seismic analyses of β Cephei stars show that it is not obvious to derive a one-to-one extent of this extra-mixed zone.
A rather large extent seems to be required to model θ Ophiuchi while a much smaller one is favored for HD 129929, for β Canis Majoris, for δ Ceti, and for 12 Lacertae.
This extra-mixed zone could even be absent in the structure of V1449 Aquilae (HD 180642) and ν Eridani.
It would be extremely interesting to establish a relation between the extent of this zone and the rotation velocity and/or the magnetic field of the star.
Seismic analysis of V2052 Ophiuchi shows that this star although rapidly rotating, which would favor extra-mixing, could be devoid of such a region.
The magnetic field detected in this star could be the reason of this lack of extra-mixing.

Be stars: Late Be type stars HD 181231 and HD 175869 are very rapid rotators, about 20 times more rapid than the Sun.
Their seismic analysis seems to require a centrally mixed zone about 20% larger than what is expected from convection only.
Another Be star, HD 49330, had a very exciting surprise in store.
Observed by CoRoT during an outburst of matter towards its circumstellar disk, which is typical of such stars, its frequency spectrum suffered drastic changes.
Firstly dominated by acoustic modes the spectrum showed the appearance of gravity modes with amplitudes strictly in line with the outburst.
Such a link between the nature of the excited modes and a dynamical phenomenon is of course a gold mine in our quest for the internal structure of Be stars.

O stars: A bunch of O stars have been observed by CoRoT. Among them HD 46150 and HD 46223 (members of the galactic cluster NGC 2264) and HD 46966 (member of the OB association Mon OB2) do not seem to pulsate, which is in agreement with stellar modeling of stars with similar global parameters.
The frequency spectrum of the Plaskett's star HD 47129 on the contrary shows a peak with six harmonics in the frequency range expected from theoretical modeling.

Another unexpected CoRoT discovery was the presence of solar-like oscillations in massive stars.
The small convective shell related to the opacity peak resulting from the ionization of iron group elements at about 200 000 K (iron opacity peak) could indeed be responsible for the stochastic excitation of acoustic modes like those observed in our Sun.

V1449 Aquilae (HD 180642): This CoRoT target is a β Cephei star whose frequency spectrum reveals high frequency and very small amplitude acoustic modes.
A careful analysis has shown that they were solar-like oscillations excited by turbulent bubbles origination from this convective iron opacity peak zone or even from the convective core.
This is indeed a major discovery since it was the first time that pulsations excited by the κ mechanism acting in the iron opacity peak zone were present side by side in the same star with pulsations stochastically excited by this very same zone.
This is the reason why Kevin Belkacem, main discoverer of these solar-like oscillations in V1449 Aquilae, added a new baptismal certificate to this β Cephei star and named it Chimera.
The figure illustrates the behavior of the frequency versus time for two modes in the frequency spectrum of Chimera, a solar-like mode (top) and a β Cephei mode (b
Massive variable main sequence stars have frequency spectra dominated by acoustic modes excited by the κ mechanism at work in layers where partial ionization of iron group elements produce a peak in opacity. In addition the most advanced of these stars present mixed modes i.e. modes with a g-character in deep layers and p-character in the envelope. Hydrogen burning takes place in a convective core surrounded by a region of varying chemical composition and an envelope mostly radiative except for tiny convective layers related to partial ionization of helium and/or iron group elements. As in lower mass stars the extent of the fully or partially mixed region located just above the convective core (extra-mixed zone) is one of the main uncertainties affecting theoretical modeling.
β Cephei stars: Seismic analyses of β Cephei stars show that it is not obvious to derive a one-to-one extent of this extra-mixed zone. A rather large extent seems to be required to model θ Ophiuchi while a much smaller one is favored for HD 129929, for β Canis Majoris, for δ Ceti, and for 12 Lacertae. This extra-mixed zone could even be absent in the structure of V1449 Aquilae (HD 180642) and ν Eridani. It would be extremely interesting to establish a relation between the extent of this zone and the rotation velocity and/or the magnetic field of the star. Seismic analysis of V2052 Ophiuchi shows that this star although rapidly rotating, which would favor extra-mixing, could be devoid of such a region. The magnetic field detected in this star could be the reason of this lack of extra-mixing.
Be stars: Late Be type stars HD 181231 and HD 175869 are very rapid rotators, about 20 times more rapid than the Sun. Their seismic analysis seems to require a centrally mixed zone about 20% larger than what is expected from convection only. Another Be star, HD 49330, had a very exciting surprise in store. Observed by CoRoT during an outburst of matter towards its circumstellar disk, which is typical of such stars, its frequency spectrum suffered drastic changes. Firstly dominated by acoustic modes the spectrum showed the appearance of gravity modes with amplitudes strictly in line with the outburst. Such a link between the nature of the excited modes and a dynamical phenomenon is of course a gold mine in our quest for the internal structure of Be stars.
O stars: A bunch of O stars have been observed by CoRoT. Among them HD 46150 and HD 46223 (members of the galactic cluster NGC 2264) and HD 46966 (member of the OB association Mon OB2) do not seem to pulsate, which is in agreement with stellar modeling of stars with similar global parameters. The frequency spectrum of the Plaskett's star HD 47129 on the contrary shows a peak with six harmonics in the frequency range expected from theoretical modeling.
Another unexpected CoRoT discovery was the presence of solar-like oscillations in massive stars. The small convective shell related to the opacity peak resulting from the ionization of iron group elements at about 200 000 K (iron opacity peak) could indeed be responsible for the stochastic excitation of acoustic modes like those observed in our Sun.
V1449 Aquilae (HD 180642): This CoRoT target is a β Cephei star whose frequency spectrum reveals high frequency and very small amplitude acoustic modes. A careful analysis has shown that they were solar-like oscillations excited by turbulent bubbles origination from this convective iron opacity peak zone or even from the convective core. This is indeed a major discovery since it was the first time that pulsations excited by the κ mechanism acting in the iron opacity peak zone were present side by side in the same star with pulsations stochastically excited by this very same zone. This is the reason why Kevin Belkacem, main discoverer of these solar-like oscillations in V1449 Aquilae, added a new baptismal certificate to this β Cephei star and named it Chimera. The figure illustrates the behavior of the frequency versus time for two modes in the frequency spectrum of Chimera, a solar-like mode (top) and a β Cephei mode (b
CoRoT