A comprehensive study of young B stars in NGC 2264

Zwintz, K.; Moravveji, E.; Pápics, P. I.; Tkachenko, A.; Przybilla, N.; Nieva, M. F.; Kuschnig, R.; Antoci, V.; Lorenz, D.; Themeßl, Nathalie; Fossati, L.; Barnes, Thomas G.

doi:10.1051/0004-6361/201630327

Cited by 17 publications

(23 citation statements)

References 77 publications

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“…More gravity-mode pulsators than those treated here are under study, but they either have too few unambiguously identified modes to derive Ω core (e.g., Zwintz et al 2017) or they have not been observed in spectroscopy to derive their v sin i and log g (e.g., Ouazzani et al 2017). Including all those with identified modes but without a spectroscopic log g in Fig.…”

Section: Discussionmentioning

confidence: 98%

The Interior Angular Momentum of Core Hydrogen Burning Stars from Gravity-mode Oscillations

Aerts

Reeth

Tkachenko

2017

ApJL

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A major uncertainty in the theory of stellar evolution is the angular momentum distribution inside stars and its change during stellar life. We compose a sample of 67 stars in the core-hydrogen burning phase with a log g value from high-resolution spectroscopy, as well as an asteroseismic estimate of the near-core rotation rate derived from gravity-mode oscillations detected in space photometry. This assembly includes 8 B-type stars and 59 AF-type stars, covering a mass range from 1.4 to 5 M ⊙ , i.e., it concerns intermediate-mass stars born with a well-developed convective core. The sample covers projected surface rotation velocities v sin i ∈ [9, 242] km s −1 and core rotation rates up to 26µHz, which corresponds to 50% of the critical rotation frequency. We find deviations from rigid rotation to be moderate in the single stars of this sample. We place the near-core rotation rates in an evolutionary context and find that the core rotation must drop drastically before or during the short phase between the end of the core-hydrogen burning and the onset of core-helium burning. We compute the spin parameter, which is the ratio of twice the rotation rate to the mode frequency (also known as the inverse Rossby number), for 1682 gravity modes and find the majority (95%) to occur in the subinertial regime. The ten stars with Rossby modes have spin parameters between 14 and 30, while the gravito-inertial modes cover the range from 1 to 15.

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Section: Discussionmentioning

confidence: 98%

The Interior Angular Momentum of Core Hydrogen Burning Stars from Gravity-mode Oscillations

Aerts

Reeth

Tkachenko

2017

ApJL

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“…Separate regressions for the log g subgroups are given for KIC and Huber et al (2014) values. been found to be almost rigidly rotating or have weak differential rotation (Degroote et al 2010;Kurtz et al 2014;Pápics et al 2014;Saio et al 2015;Van Reeth et al 2015a;Triana et al 2015;Murphy et al 2016;Ouazzani et al 2017;Pápics et al 2017;Zwintz et al 2017;Van Reeth et al 2018).…”

Section: Low-frequency Variability In δ Sct Starsmentioning

confidence: 99%

Characterizing the observational properties of δ Sct stars in the era of space photometry from the Kepler mission

Bowman

Kurtz

2018

Monthly Notices of the Royal Astronomical Society

121

102

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The δ Sct stars are a diverse group of intermediate-mass pulsating stars located on and near the main sequence within the classical instability strip in the Hertzsprung-Russell diagram. Many of these stars are hybrid stars pulsating simultaneously with pressure and gravity modes that probe the physics at different depths within a star's interior. Using two large ensembles of δ Sct stars observed by the Kepler Space Telescope, the instrumental biases inherent to Kepler mission data and the statistical properties of these stars are investigated. An important focus of this work is an analysis of the relationships between the pulsational and stellar parameters, and their distribution within the classical instability strip. It is found that a non-negligible fraction of main sequence δ Sct stars exist outside theoretical predictions of the classical instability boundaries, which indicates the necessity of a mass-dependent mixing length parameter to simultaneously explain low-and high-radial order pressure modes in δ Sct stars within the Hertzsprung-Russell diagram. Furthermore, a search for regularities in the amplitude spectra of these stars is also presented, specifically the frequency difference between pressure modes of consecutive radial order. In this work, it is demonstrated that an ensemble-based approach using space photometry from the Kepler mission is not only plausible for δ Sct stars, but that it is a valuable method for identifying the most promising stars for mode identification and asteroseismic modelling. The full scientific potential of studying δ Sct stars is as yet unrealised. The ensembles discussed in this paper represent a high-quality data set for future studies of rotation and angular momentum transport inside A and F stars using asteroseismology.

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“…The detection of internal gravity waves, which propagate to the bottom of a star's radiative zone, provides precious information about the cores and interiors of massive stars (e.g., Zwintz et al 2017;Ouazzani et al 2019). Bowman et al (2019a, hereafter B19) detected low-frequency variability in a large population of mas-sive stars (following similar detections in fewer stars by, e.g., Blomme et al 2011).…”

Section: Introductionmentioning

confidence: 99%

Low-frequency Variability in Massive Stars: Core Generation or Surface Phenomenon?

Lecoanet

Cantiello

Quataert

et al. 2019

ApJL

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Bowman et al. (2019a) reported low-frequency photometric variability in 164 O-and B-type stars observed with K2 and TESS. They interpret these motions as internal gravity waves, which could be excited stochastically by convection in the cores of these stars. The detection of internal gravity waves in massive stars would help distinguish between massive stars with convective or radiative cores, determine core size, and would provide important constraints on massive star structure and evolution. In this work, we study the observational signature of internal gravity waves generated by core convection. We calculate the wave transfer function, which links the internal gravity wave amplitude at the base of the radiative zone to the surface luminosity variation. This transfer function varies by many orders of magnitude for frequencies 1 d −1 , and has regularly-spaced peaks near 1 d −1 due to standing modes. This is inconsistent with the observed spectra which have smooth "red noise" profiles, without the predicted regularly-spaced peaks. The wave transfer function is only meaningful if the waves stay predominatly linear. We next show that this is the case: low frequency traveling waves do not break unless their luminosity exceeds the radiative luminosity of the star; and, the observed luminosity fluctuations at high frequencies are so small that standing modes would be stable to nonlinear instability. These simple calculations suggest that the observed low-frequency photometric variability in massive stars is not due to internal gravity waves generated in the core of these stars. We finish with a discussion of (sub)surface convection, which produces low-frequency variability in low-mass stars, very similar to that observed in Bowman et al. (2019a) in higher mass stars.

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A comprehensive study of young B stars in NGC 2264

Cited by 17 publications

References 77 publications

The Interior Angular Momentum of Core Hydrogen Burning Stars from Gravity-mode Oscillations

The Interior Angular Momentum of Core Hydrogen Burning Stars from Gravity-mode Oscillations

Characterizing the observational properties of δ Sct stars in the era of space photometry from the Kepler mission

Low-frequency Variability in Massive Stars: Core Generation or Surface Phenomenon?

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