Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452

Neiner, C.; Floquet, M.; Samadi, R.; Lara, F. Espinosa; Frémat, Y.; Mathis, S.; Leroy, B.; Batz, B. de; Rainer, M.; Poretti, E.; Mathias, P.; Fló, J. Guarro; Buil, C.; Ribeiro, José Pancrácio; Alécian, E.; Andrade, L.; Briquet, Maryline; Diago, P. D.; Emílio, M.; Fabregat, J.; Gutiérrez‐Soto, J.; Hubert, A. M.; Janot-Pacheco, E.; Martayan, C.; Semaan, T.; Suso, J.; Zorec, J.

doi:10.1051/0004-6361/201219820

Cited by 71 publications

(85 citation statements)

References 34 publications

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“…Unno et al 1989;Gastine & Dintrans 2008) and stochastic motions in both the bulk of convective regions and at their interfaces with adjacent radiation zones where turbulent convective structures (plumes) penetrate because of their inertia (e.g. Press 1981;Browning et al 2004;Rogers & Glatzmaier 2005;Belkacem et al 2009b;A&A 565, A47 (2014) (Neiner et al 2012). In this star, which rotates close to its critical angular velocity, we discovered gravity modes that are strongly influenced by the Coriolis acceleration that are gravito-inertial modes (Dintrans & Rieutord 2000;Mathis 2009;Ballot et al 2010).…”

Section: Introductionmentioning

confidence: 60%

“…When such waves (or their signatures) are detected by means of helioseismology (Garcia et al 2007) and asteroseismology (e.g. Beck et al 2011;Pápics et al 2012;Neiner et al 2012), they constitute a powerful probe of stellar structure (e.g. Turck-Chièze & Couvidat 2011;Bedding et al 2011) and internal dynamics, for example of differential rotation (Garcia et al 2007;Beck et al 2012;Deheuvels et al 2012;Mosser et al 2012).…”

Section: Introductionmentioning

confidence: 99%

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Impact of rotation on stochastic excitation of gravity and gravito-inertial waves in stars

Mathis

Neiner

Minh

2014

A&A

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Context. Gravity waves (or their signatures) are detected in stars thanks to helio-and asteroseismology, and they may play an important role in the evolution of stellar angular momentum. Moreover, a previous observational study of the CoRoT target HD 51452 demonstrated the potential strong impact of rotation on the stochastic excitation of gravito-inertial waves in stellar interiors. Aims. Our goal is to explore and unravel the action of rotation on the stochastic excitation of gravity and gravito-inertial waves in stars.Methods. The dynamics of gravito-inertial waves in stellar interiors in both radiation and in convection zones is described with a local non-traditional f -plane model. The coupling of these waves with convective turbulent flows, which leads to their stochastic excitation, is studied in this framework. Results. First, we find that in the super-inertial regime in which the wave frequency is twice as high as the rotation frequency (σ > 2Ω), the evanescence of gravito-inertial waves in convective regions decreases with decreasing wave frequency. Next, in the sub-inertial regime (σ < 2Ω), gravito-inertial waves become purely propagative inertial waves in convection zones. Simultaneously, turbulence in convective regions is modified by rotation. Indeed, the turbulent energy cascade towards small scales is slowed down, and in the case of rapid rotation, strongly anisotropic turbulent flows are obtained that can be understood as complex non-linear triadic interactions of propagative inertial waves. These different behaviours, due to the action of the Coriolis acceleration, strongly modify the wave coupling with turbulent flows. On one hand, turbulence weakly influenced by rotation is coupled with evanescent gravitoinertial waves. On the other hand, rapidly rotating turbulence is intrinsically and strongly coupled with sub-inertial waves. Finally, to study these mechanisms, the traditional approximation cannot be assumed because it does not properly treat the coupling between gravity and inertial waves in the sub-inertial regime.Conclusions. Our results demonstrate the action of rotation on stochastic excitation of gravity waves thanks to the Coriolis acceleration, which modifies their dynamics in rapidly rotating stars and turbulent flows. As the ratio 2Ω/σ increases, the couplings and thus the amplitude of stochastic gravity waves are amplified.

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Section: Introductionmentioning

confidence: 60%

Section: Introductionmentioning

confidence: 99%

Impact of rotation on stochastic excitation of gravity and gravito-inertial waves in stars

Mathis

Neiner

Minh

2014

A&A

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“…Such stochastic IGWs have only recently been observed for massive stars (e.g. Blomme et al 2011;Neiner et al 2012b;Aerts et al 2017). In addition, it has become clear from Kepler data that gravitoinertial modes in B-and F-type pulsators with period spacings are dipole modes (Van Reeth et al 2015;Pápics et al 2017).…”

Section: The Pulsating Magnetic Hot Star Hd 43317mentioning

confidence: 99%

Magnetic characterization of the SPB/β Cep hybrid pulsator HD 43317

Buysschaert

Neiner

Briquet

et al. 2017

A&A

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Large-scale magnetic fields at the surface of massive stars do not only influence the outer-most layers of the star, but also have consequences for the deep interior, only observationally accessible through asteroseismology. We performed a detailed characterization of the dipolar magnetic field at the surface of the B3.5V star HD 43317, a SPB/β Cep hybrid pulsator, by studying the rotationally modulated magnetic field of archival and new Narval spectropolarimetry. Additionally, we employed a grid-based approach to compare the Zeeman signatures with model profiles. By studying the rotational modulation of the He lines in both the Narval and HARPS spectroscopy caused by co-rotating surface abundance inhomogeneities, we updated the rotation period to 0.897673 ± 0.000004 d. The inclination angle between the rotation axis and the observer's line of sight remains ill-defined, because of the low level of variability in Stokes V and deformations in the intensity profiles by stellar pulsation modes. The obliquity angle between the rotation and magnetic axes is constrained to β ∈ [67, 90] • , and the strength of the dipolar magnetic field is of the order of 1 kG to 1.5 kG. This magnetic field at the stellar surface is sufficiently strong to warrant a uniformly rotating radiative envelope, causing less convective core overshooting, which should be visible in future forward seismic modeling.

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“…Indeed, theoretical and numerical simulations show that large-scale, low-frequency internal gravity waves are excited by the convective core and can transport angular momentum (Mathis 2013;Rogers et al 2013). Such waves were revealed by high-precision, space-based CoRoT photometric data in several Be (Neiner et al 2012b) and O-type stars. For the latter, a red noise power excess of physical origin was detected by Blomme et al (2011) and then interpreted as internal gravity waves by Aerts & Rogers (2015).…”

Section: Surface N-enrichment In Early B-type Starsmentioning

confidence: 99%

Weak magnetic field, solid-envelope rotation, and wave-induced N-enrichment in the SPB starζCassiopeiae

Briquet¹,

Neiner²,

Petit³

et al. 2016

A&A

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Aims. The main-sequence B-type star ζ Cassiopeiae is known as a N-rich star with a magnetic field discovered with the Musicos spectropolarimeter. We model the magnetic field of the star by means of 82 new spectropolarimetric observations of higher precision to investigate the field strength, topology, and effect. Methods. We gathered data with the Narval spectropolarimeter installed at Télescope Bernard Lyot (TBL; Pic du Midi, France) and applied the least-squares deconvolution technique to measure the circular polarisation of the light emitted from ζ Cas. We used a dipole oblique rotator model to determine the field configuration by fitting the longitudinal field measurements and by synthesizing the measured Stokes V profiles. We also made use of the Zeeman-Doppler imaging technique to map the stellar surface and to deduce the difference in rotation rate between the pole and equator. Results. ζ Cas exhibits a polar field strength B pol of 100−150 G, which is the weakest polar field observed so far in a massive mainsequence star. Surface differential rotation is ruled out by our observations and the field of ζ Cas is strong enough to enforce rigid internal rotation in the radiative zone according to theory. Thus, the star rotates as a solid body in the envelope. Conclusions. We therefore exclude rotationally induced mixing as the cause of the surface N-enrichment. We discuss that the transport of chemicals from the core to the surface by internal gravity waves is the most plausible explanation for the nitrogen overabundance at the surface of ζ Cas.

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Stochastic gravito-inertial modes discovered by CoRoT in the hot Be star HD 51452

Cited by 71 publications

References 34 publications

Impact of rotation on stochastic excitation of gravity and gravito-inertial waves in stars

Impact of rotation on stochastic excitation of gravity and gravito-inertial waves in stars

Magnetic characterization of the SPB/β Cep hybrid pulsator HD 43317

Weak magnetic field, solid-envelope rotation, and wave-induced N-enrichment in the SPB starζCassiopeiae

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