CoRoT Measures Solar-Like Oscillations and Granulation in Stars Hotter Than the Sun

Michel, E.; Baglin, A.; Auvergne, M.; Catala, C.; Samadi, R.; Baudin, F.; Appourchaux, T.; Barban, C.; Weiß, W. W.; Berthomieu, G.; Boumier, P.; Dupret, Marc‐Antoine; García, Rafael A.; Fridlund, M.; Garrido, R.; Goupil, M. J.; Kjeldsen, H.; Lebreton, Y.; Mosser, B.; Grötsch-Noels, A.; Janot-Pacheco, E.; Provost, J.; Roxburgh, I. W.; Thoul, Anne; Toutain, T.; Tiphéne, D.; Turck‐Chièze, S.; Vauclair, S.; Vauclair, G.; Aerts, C.; Alecian, G.; Ballot, J.; Charpinet, S.; Hubert, A. M.; Lignières, F.; Mathias, P.; Monteiro, M. J. P. F. G.; Neiner, C.; Poretti, E.; Medeiros, J. R. De; Ribas, I.; Rieutord, M.; Cortés, T. Roca; Zwintz, K.

doi:10.1126/science.1163004

Cited by 208 publications

(169 citation statements)

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“…The seismic interpretation of the detected solar oscillations led to a drastic improvement in the knowledge of the internal structure of the Sun 10,11 . Meanwhile, similar acoustic modes have been detected in various types of distant stars [12][13][14] . Gravity modes, on the other hand, probe much deeper layers inside stars and in principle allow the study of the core properties of stars far better than acoustic modes.…”

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confidence: 91%

Deviations from a uniform period spacing of gravity modes in a massive star

Degroote

Aerts

Baglin

et al. 2010

Nature

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The life of a star is dominantly determined by the physical processes in the stellar interior. Unfortunately, we still have a poor understanding of how the stellar gas mixes near the stellar core, preventing precise predictions of stellar evolution 1 . The unknown nature of the mixing processes as well as the extent of the central mixed region is particularly problematic for massive stars 2 . Oscillations in stars with masses a few times that of the Sun offer a unique opportunity to disentangle the nature of various mixing processes, through the distinct signature they leave on period spacings in the gravity mode spectrum 3 . Here we report the detection of numerous gravity modes in a young star with a mass of about seven solar masses. The mean period spacing allows us to estimate the extent of the convective core, and the clear periodic deviation from the mean constrains the location of the chemical transition zone to be at about 10 per cent of the radius and rules out a clearcut profile.The young massive star HD 50230 is poorly studied, but it is known to have spectral type B3V and a visual magnitude of 8.95. HD 50230 is in its central nuclear-burning phase, just like the Sun, transforming hydrogen into helium in its core (the so-called main sequence phase). This important evolutionary phase covers about 90% of the life of the star, and the detailed internal structure of the star during this phase determines its ultimate fate 1,2 . This star is at the limiting mass of ending either as core-collapse supernova or as a white dwarf, enriching the interstellar medium with helium and heavy metals in the former case and carbon in the latter. A highquality continuous photometric light curve with 32-s sampling and with a span of 137 days has been obtained for the star by the Convection Rotation and Planetary Transits (CoRoT 4 ) satellite. A linear downward trend was removed from the data, after outliers were excluded from the light curve. The duty cycle of the final set of measurements analysed here is 88.6% and the noise has an amplitude of 1 mmag (Fig. 1). The light curve reveals the presence of numerous oscillation modes.Stellar oscillations have been found to occur at different stages of stellar life, for a range of stellar masses 5 . The best known case is that of the solar oscillations, which are acoustic modes with periods near 5 min (refs 6-9). The seismic interpretation of the detected solar oscillations led to a drastic improvement in the knowledge of the internal structure of the Sun 10,11 . Meanwhile, similar acoustic modes have been detected in various types of distant stars [12][13][14] . Gravity modes, on the other hand, probe much deeper layers inside stars and in principle allow the study of the core properties of stars far better than acoustic modes. Although such modes have been detected in massive stars similar to HD 50230 15,16 , where they have typical periods of half a day to a few days, their seismic potential could not be exploited because the number of detected modes in one star was far too lo...

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confidence: 91%

Deviations from a uniform period spacing of gravity modes in a massive star

Degroote

Aerts

Baglin

et al. 2010

Nature

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208

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“…Bedding & Kjeldsen 2007, and references thereafter), which was made possible by the development of a new generation of spectrographs with high enough precision to detect the small amplitudes (typically of a few tens of cm/s) of stochastically-driven oscillations, in stars other than the Sun. Since then, observations of pulsating stars from space have also become possible, first with the tiny 5 cm star tracker mounted on the NASA WIRE satellite (Buzasi et al 2000), followed by the 15 cm Canadian-led satellite MOST (Walker et al 2003) and the 27 cm French-led satellite CoRoT (Michel et al 2008). These satellites and high-precision, ground-based, campaigns conducted in the past few years (e.g.…”

Section: Introductionmentioning

confidence: 99%

Probing tiny convective cores with the acoustic modes of lowest degree

Cunha

Brandão

2011

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Solar-like oscillations are expected to be excited in stars of up to about 1.6 solar masses. Most of these stars will have convective cores during their main-sequence evolution. At the edges of these convective cores, there is a rapid variation in the sound speed, which influences the frequencies of acoustic oscillations. In this paper we build on earlier work to investigate the impact that these rapid structural variations have on different p-mode frequency combinations, involving modes of low degree. In particular, we adopt a different expression to describe the sound speed variation at the edge of the core, which we show more closely reproduces the profiles derived from the equilibrium models. We analyse the impact of this change on the frequency perturbation derived for radial modes. Moreover, we consider three different small frequency separations involving modes of degree l = 0, 1, 2, 3, l = 0, 1, and l = 0, 2, and show that they are all significantly affected by the sharp sound speed variation at the edge of the core. In particular, we confirm that the frequency derivative of the diagnostic tool that combines modes of degree up to 3 can potentially be used to infer the amplitude of the relative sound speed variation directly at the edge of the core. We show that at high frequencies the other two diagnostic tools can be up to a few μHz smaller than what would be expected in the absence of the rapid structural variation at the edge of the core. Also, we show that the absolute values of their frequency derivatives are significantly increased, in a manner that strongly depends on stellar age.

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“…Stochastically excited modes have only been predicted and detected in solar-like and red giant stars (see Bedding & Kjeldsen 2007;Michel et al 2008;de Ridder et al 2009, for details). The data gathered by the CoRoT mission has allowed us to report the first detection of solar-like oscillations in a massive star, V1449 Aql (Belkacem et al 2009b).…”

Section: Introductionmentioning

confidence: 99%

Solar-like oscillations in massive main-sequence stars

Belkacem¹,

Dupret²,

Noels³

2010

A&A

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Motivated by the detection of stochastically excited modes in the massive star V1449 Aql, which is already known to be a β Cephei star, we theoretically investigate the driving by turbulent convection. By using a full non-adiabatic computation of the damping rates, together with a computation of the energy injection rates, we provide an estimate of the amplitudes of modes excited by both the convective region induced by the iron opacity bump and the convective core. Despite the uncertainties in the dynamical properties of these convective regions, we demonstrate that both regions are able to efficiently excite p modes above the CoRoT observational threshold and the solar amplitudes. In addition, we emphasise the potential asteroseismic diagnostics provided by each convective region, which we hope will help us to identify the region responsible for solar-like oscillations, and to place constraints on this convective zone. A forthcoming work will be dedicated to an extended investigation of the likelihood of solar-like oscillations across the Hertzsprung-Russell diagram.

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CoRoT Measures Solar-Like Oscillations and Granulation in Stars Hotter Than the Sun

Cited by 208 publications

References 14 publications

Deviations from a uniform period spacing of gravity modes in a massive star

Deviations from a uniform period spacing of gravity modes in a massive star

Probing tiny convective cores with the acoustic modes of lowest degree

Solar-like oscillations in massive main-sequence stars

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