Introducing Asteroseismology

Aerts, C.; Christensen‐Dalsgaard, J.; Kurtz, D. W.

doi:10.1007/978-1-4020-5803-5_1

Cited by 9 publications

(14 citation statements)

References 1,317 publications

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“…On or near the main sequence, these pulsations are usually driven by a heat mechanism acting in the metal opacity bump at a temperature near 200 000 degrees (e.g., Cox et al 1992;Pamyatnyh 1999). In the recent and rapidly growing research field of asteroseismology, observed pulsations are exploited by scientists to probe the poorly known physical processes inside stars (e.g., Cunha et al 2007;Aerts et al 2009), as was done in helioseismology for the Sun (e.g., Gough et al 1996). Asteroseismology was proven to be a valid tool to study the interior of massive main-sequence stars (e.g., and may be a unique opportunity to probe the internal layers, including the deep convection zone around the hydrogenburning shell, of evolved stars as well.…”

Section: Computations Of Pulsationally Broadened Spectral Line Profilesmentioning

confidence: 99%

“…The discovery of gravitymode pulsations in the B1Ib supergiant HD 163899 from spacebased high-precision photometry measured with the Canadian space mission MOST (Saio et al 2006) and in a sample of 40 B supergiants (Lefever et al 2007) are steps in this direction. We refer the reader to Aerts et al (2009) for a thorough description of stellar pulsation in all of its aspects, including the particular properties of the eigenfrequencies and eigenfunctions of pressure and gravity modes. It is well known that stellar pulsations imply a timedependent variation of the shape of spectral lines (e.g., Aerts & De Cat 2003, for a review, Chaps.…”

Section: Computations Of Pulsationally Broadened Spectral Line Profilesmentioning

confidence: 99%

“…We considered all modes up to degree ten, as it is well-known that partial geometrical cancellation effects increase with increasing mode degree (e.g., Chap. 6 of Aerts et al 2009, for a full description of these effects) and, moreover, we needed to keep the computation time feasible. We found 241 modes with degree from 1 to 10 to be excited.…”

Section: Input For the Simulationsmentioning

confidence: 99%

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Collective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars

Aerts

Puls²,

Godart

et al. 2009

A&A

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137

195

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Aims. We aimed at finding a physical explanation for the occurrence of macroturbulence in the atmospheres of hot massive stars, a phenomenon found in observations for more than a decade but that remains unexplained. Methods. We computed time series of line profiles for evolved massive stars broadened by rotation and by hundreds of low-amplitude nonradial gravity-mode pulsations which are predicted to be excited for evolved massive stars. Results. In general, line profiles based on macrotubulent broadening can mimic those subject to pulsational broadening. In several cases, though, good fits require macroturbulent velocities that pass the speed of sound for realistic pulsation amplitudes. Moreover, we find that the rotation velocity can be seriously underestimated by using a simple parameter description for macroturbulence rather than an appropriate pulsational model description to fit the line profiles. Conclusions. We conclude that macroturbulence is a likely signature of the collective effect of pulsations. We provide line diagnostics and their typical values to decide whether or not pulsational broadening is present in observed line profiles, as well as a procedure to avoid an inaccurate estimation of the rotation velocity.

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Section: Computations Of Pulsationally Broadened Spectral Line Profilesmentioning

confidence: 99%

Section: Computations Of Pulsationally Broadened Spectral Line Profilesmentioning

confidence: 99%

Section: Input For the Simulationsmentioning

confidence: 99%

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Collective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars

Aerts

Puls²,

Godart

et al. 2009

A&A

Self Cite

137

195

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“…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).…”

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confidence: 99%

“…17). The oscillation period content in the data was extracted using classical and short-time Fourier analysis techniques, combined with nonlinear fitting of the light curve 5 , and a search for a recurrent period spacing was conducted 18 . A group of eight consecutive periods with an almost constant spacing of 9,418 s was detected in the data (Fig.…”

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confidence: 99%

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

Degroote

Aerts

Baglin

et al. 2010

Nature

163

211

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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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Prospects for asteroseismology

Christensen‐Dalsgaard

Houdek

2009

Astrophys Space Sci

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The observational basis for asteroseismology is being dramatically strengthened, through more than two years of data from the CoRoT satellite, the flood of data coming from the Kepler mission and, in the slightly longer term, from dedicated ground-based facilities. Our ability to utilize these data depends on further development of techniques for basic data analysis, as well as on an improved understanding of the relation between the observed frequencies and the underlying properties of the stars. Also, stellar modelling must be further developed, to match the increasing diagnostic potential of the data. Here we discuss some aspects of data interpretation and modelling, focussing on the important case of stars with solar-like oscillations.Comment: Proc. HELAS Workshop on 'Synergies between solar and stellar modelling', eds M. Marconi, D. Cardini & M. P. Di Mauro, Astrophys. Space Sci., in the press Revision: correcting abscissa labels on Figs 1 and

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Introducing Asteroseismology

Cited by 9 publications

References 1,317 publications

Collective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars

Collective pulsational velocity broadening due to gravity modes as a physical explanation for macroturbulence in hot massive stars

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

Prospects for asteroseismology

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