Deciphering the oscillation spectrum of <i>γ</i> Doradus and SPB stars

Christophe, S.; Ballot, J.; Ouazzani, R. M.; Antoci, V.; Salmon, Sébastien

doi:10.1051/0004-6361/201832782

Cited by 64 publications

(86 citation statements)

References 63 publications

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“…For fast rotators, as in the majority of γ Dor stars, the period spacings change quasi-linearly with period and can be used to fit the near-core rotation rate (e.g. Van Reeth et al 2016;Christophe et al 2018). Now, splittings or period spacings of g modes from tens of γ Dor stars were found, both in single stars and binaries, whose rotation profiles are almost uniform (e.g.…”

Section: Introductionmentioning

confidence: 99%

Gravity-mode period spacings and near-core rotation rates of 611 γ Doradus stars with Kepler

Reeth

Bedding

et al. 2019

Monthly Notices of the Royal Astronomical Society

115

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We report our survey of γ Dor stars from the 4-yr Kepler mission. These stars pulsate mainly in g modes and r modes, showing period-spacing patterns in the amplitude spectra. The period-spacing patterns are sensitive to the chemical composition gradients and the near-core rotation, hence they are essential for understanding the stellar interior. We identified period-spacing patterns in 611 γ Dor stars. Almost every star pulsates in dipole g modes, while about 30% of stars also show clear patterns for quadrupole g modes and 16% of stars present r mode patterns. We measure periods, period spacings, and the gradient of the period spacings. These three observables guide the mode identifications and can be used to estimate the near-core rotation rate. We find many stars are hotter and show longer period-spacing patterns than theory. Using the Traditional Approximation of Rotation (TAR), we inferred the asymptotic spacings, the near-core rotation rates, and the radial orders of the g and r modes. Most stars have a near-core rotation rate around 1 d −1 and an asymptotic spacing around 4000 s. We also find that many stars rotate more slowly than predicted by theory for unclear reasons. 11 stars show rotational splittings with fast rotation rates. We compared the observed slope-rotation relation with the theory and find a large spread. We detected rotational modulations in 58 stars and used them to derive the core-tosurface rotation ratios. The interiors rotate faster than the cores in most stars, but by no more than 5%.

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Section: Introductionmentioning

confidence: 99%

Gravity-mode period spacings and near-core rotation rates of 611 γ Doradus stars with Kepler

Reeth

Bedding

et al. 2019

Monthly Notices of the Royal Astronomical Society

115

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“…However, most γ Dor stars rotate rapidly and the period spacings change significantly with period (e.g. Bedding et al 2015;Van Reeth et al 2015a;Saio et al 2018b;Christophe et al 2018). Besides g-modes, r-modes were also found in γ Dor stars by Van Reeth et al (2016) and Saio et al (2018a).…”

Section: Introductionmentioning

confidence: 99%

Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars

Reeth

Bedding

et al. 2019

Monthly Notices of the Royal Astronomical Society

110

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Rossby modes are the oscillations in a rotating fluid, whose restoring force is the Coriolis force. They provide an additional diagnostic to understand the rotation of stars, which complicates asteroseismic modelling. We report 82 γ Doradus stars for which clear period spacing patterns of both gravity and Rossby modes have been detected. The period spacings of both show a quasi-linear relation with the pulsation period but the slope is negative for the gravity modes and positive for the Rossby modes. Most Rossby modes have k = −2, m = −1. For only one star a series of k = −1, m = −1 modes is seen. For each pattern, the mean pulsation period, the mean period spacing, and the slope are measured. We find that the slope correlates with the mean period for Rossby mode patterns. The traditional approximation of rotation is used to measure the near-core rotation rate, assuming the star rotates rigidly. We report the near-core rotation rates, the asymptotic period spacings, and the radial orders of excited modes of these 82 main-sequence stars. The near-core rotation rates lie between 0.6 d −1 and 2.3 d −1 . Six stars show surface rotation modulations, among which only KIC 3341457 shows differential rotation while the other five stars have uniform rotations. The radial orders of excited modes show different distributions for the dipole and quadrupole gravity modes versus the Rossby modes.

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“…Van Reeth et al (2016), for example, use a large grid of evolutionary models with an assumed range of rotation rates to find the bestfitting parameters for their sample of stars, including the rotation rates. On the other hand, Christophe et al (2018) propose a model-independent method based on the discrete Fourier transform. The basic idea is that the pulsation periods will be evenly spaced even when the star is rapidly rotating if the period coordinate is stretched appropriately.…”

Section: Introductionmentioning

confidence: 99%

A diagnostic diagram for γ Doradus variables and slowly pulsating B-type stars

Takata

Ouazzani

Saio

et al. 2020

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Pulsating variables of γ Doradus type (γ Dor) and slowly pulsating B-type (SPB) stars are found on and near the main sequence with typical periods varying between one and several days, making them rather hard to detect from the ground. It is only with space missions such as CoRoT and Kepler that we became truly capable of determining their oscillation frequencies with enough precision to perform in-depth analyses. Here we present an efficient and easy-to-implement seismic tool, in which the frequency (ν) and the square root of the frequency difference ($ \sqrt{\Delta \nu} $) are plotted against each other as the abscissa and the ordinate, respectively. This allows us to immediately (1) perform mode identification; (2) estimate the average rotation rate and the characteristic period of gravity modes; and (3) recognise certain physical effects, including buoyancy glitches and avoided crossings. This diagnostic tool can only be applied to prograde sectoral g modes. To validate the tool presented here, we used stellar models and also applied it to three γ Dor (KIC 12066947, KIC 5608334 and KIC 4846809) and one SPB star (KIC 3459297), all observed with Kepler. Furthermore, we show that the rotation rates determined using this new tool are consistent with the results of previous studies.

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Deciphering the oscillation spectrum of γ Doradus and SPB stars

Cited by 64 publications

References 63 publications

Gravity-mode period spacings and near-core rotation rates of 611 γ Doradus stars with Kepler

Gravity-mode period spacings and near-core rotation rates of 611 γ Doradus stars with Kepler

Period spacings of γ Doradus pulsators in the Kepler field: Rossby and gravity modes in 82 stars

A diagnostic diagram for γ Doradus variables and slowly pulsating B-type stars

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