Oscillations in rapidly rotating stars

Reese, D. R.

doi:10.1002/asna.201011452

Cited by 13 publications

(9 citation statements)

References 80 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Finally, we note that all of these methods can also be used to account for the effects of rotation or magnetic fields (e.g. Shibahashi & Takata 1993;Reese 2010). Coupling between modes of different also occurs in rotating stars, but the axisymmetry of that problem means that the mode amplitude is not modulated with rotational phase.…”

Section: Mathematical Formalismmentioning

confidence: 99%

Tidally trapped pulsations in binary stars

Fuller

Kurtz

Handler

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

A new class of pulsating binary stars was recently discovered, whose pulsation amplitudes are strongly modulated with orbital phase. Stars in close binaries are tidally distorted, so we examine how a star’s tidally induced asphericity affects its oscillation mode frequencies and eigenfunctions. We explain the pulsation amplitude modulation via tidal mode coupling such that the pulsations are effectively confined to certain regions of the star, e.g., the tidal pole or the tidal equator. In addition to a rigorous mathematical formalism to compute this coupling, we provide a more intuitive semi-analytic description of the process. We discuss three resulting effects: 1. Tidal alignment, i.e., the alignment of oscillation modes about the tidal axis rather than the rotation axis; 2. Tidal trapping, e.g., the confinement of oscillations near the tidal poles or the tidal equator; 3. Tidal amplification, i.e., increased flux perturbations near the tidal poles where acoustic modes can propagate closer to the surface of the star. Together, these phenomena can account for the pulsation amplitude and phase modulation of the recently discovered class of “tidally tilted pulsators.” We compare our theory to the three tidally tilted pulsators HD 74423, CO Cam, and TIC 63328020, finding that tidally trapped modes that are axisymmetric about the tidal axis can largely explain the first two, while a non-axisymmetric tidally aligned mode is present in the latter. Finally, we discuss implications and limitations of the theory, and we make predictions for the many new tidally tilted pulsators likely to be discovered in the near future.

show abstract

Section: Mathematical Formalismmentioning

confidence: 99%

Tidally trapped pulsations in binary stars

Fuller

Kurtz

Handler

et al. 2020

Monthly Notices of the Royal Astronomical Society

View full text Add to dashboard Cite

show abstract

“…3.1.2), to model the non-radial pulsations of the two rapidly rotating Be stars. This code includes the effects of the centrifugal acceleration (which breaks the spherical symmetry of the star as described above) and of the Coriolis acceleration, which have to be taken into account in our seismic modelling since Ω Ω c = 0.9 (see Lee 2008;Reese 2010). With this non-adiabatic oscillation code, we performed a non-radial pulsation stability analysis for rapidly rotating star models, whose evolutionary track passes close to the position of the Be stars in the HR diagram.…”

Section: Tohoku Non-adiabatic Oscillation Codementioning

confidence: 99%

Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

Neiner

Mathis

Saio

et al. 2012

A&A

View full text Add to dashboard Cite

Context. HD 181231 and HD 175869 are two late rapidly rotating Be stars, which have been observed using high-precision photometry with the CoRoT satellite during about five consecutive months and 27 consecutive days, respectively. An analysis of their light curves, by Neiner and collaborators and Gutiérrez-Soto and collaborators respectively, showed that several independent pulsation g-modes are present in these stars. Fundamental parameters have also been determined by these authors using spectroscopy. Aims. We aim to model these results to infer seismic properties of HD 181231 and HD 175869, and constrain internal transport processes of rapidly rotating massive stars. Methods. We used an adiabatic (NRO) and a non-adiabatic (Tohoku) oscillation code that accounts for the combined action of Coriolis and centrifugal accelerations on stellar pulsations as needed for rapid rotator modelling. We coupled these codes with a 2D (ROTORC) stellar structure model to take the rotational deformation of the star into account. The action of transport processes was parametrised with the mixing parameter α ov , which represents the "non-standard" extension of the convective core, and determined by matching observed pulsation frequencies assuming a single star evolution scenario. In a second step, we used (Geneva) evolution models to evaluate the contribution of the secular rotational transport and mixing processes in the radiative envelope. A Monte Carlo analysis of spectropolarimetric data was also performed to examine the role of a potential fossil magnetic field. Finally, based on state-of-the-art modelling of penetrative convection and internal waves, we unravelled their respective contribution to the needed "non-standard" mixing.Results. We find that extra mixing of α ov = 0.3−0.35H p is needed in HD 181231 and HD 175869 to match the observed frequencies with those of prograde sectoral g-modes. We also detect the possible presence of r-modes. We investigated the respective contributions of several transport processes to this mixing: the hydrodynamical processes in particular the meridional circulation and shear-induced turbulence caused by the radiative envelope differential rotation, the possible magnetic field, the penetrative convection at the top of the convective core, and the transport by internal waves. Conclusions. We showed that the extension of the convective core needed to match observations and models may be explained by mixing induced by the penetrative movements at the bottom of the radiative envelope and by the secular hydrodynamical transport processes induced by the rotation in the envelope. We showed how asteroseismology opens a new door to probe transport processes in stellar interiors.

show abstract

“…Also, the rotational splitting becomes comparable with the frequency separation between different multiplets (n, l), greatly complicating the interpretation of the observed spectra. As reviewed by Reese (2010) the perturbative description, in which Eq. (3) is the lowest order, breaks down for sufficiently rapid rotation, leading to more complex types of oscillation; in practice this happens at rotation rates such as to be relevant for many asteroseismically interesting stars.…”

Section: Effects Of Rotationmentioning

confidence: 99%

Seismological challenges for stellar structure

Christensen‐Dalsgaard

2010

Astron Nachr

View full text Add to dashboard Cite

Helioseismology has provided very detailed information about the solar interior, and extensive data on a large number of stars, although at less detail, are promised by the ongoing and upcoming asteroseismic projects. In the solar case there remain serious challenges in understanding the inferred solar structure, particularly in the light of the revised determinations of the solar surface composition. Also, a secure understanding of the origins of solar rotation as inferred from helioseismology, both in the radiative interior and in the convection zone, is still missing. In the stellar case challenges are certain to appear as the data allow more detailed inferences of the properties of stellar cores. Large remaining uncertainties in modelling concern the properties of convective cores and other processes that may cause mixing. As a result of developing asteroseismic signatures addressing these and other issues, we can look forward to a highly challenging, and hence exciting, era of stellar astrophysics.

show abstract

Oscillations in rapidly rotating stars

Cited by 13 publications

References 80 publications

Tidally trapped pulsations in binary stars

Tidally trapped pulsations in binary stars

Seismic modelling of the late Be stars HD 181231 and HD 175869 observed with CoRoT: a laboratory for mixing processes

Seismological challenges for stellar structure

Contact Info

Product

Resources

About