scholarly journals Quadratic and Cubic Couplings of Oscillation Modes of Stars

1995 ◽  
Vol 155 ◽  
pp. 287-288
Author(s):  
T. Van Hoolst
Keyword(s):  
Main Sequence ◽  
Oscillation Mode ◽  
The Self ◽  
Nonlinear Interactions ◽  
Nonlinear Coupling ◽  
Coupling Coefficients ◽  
Main Sequence Stars ◽  
Evolved Stars ◽  
Oscillation Modes ◽  
Nonradial Oscillation

The strength of nonlinear interactions of oscillation modes of stars is determined by the amplitudes as well as by the eigenfunctions of the oscillation modes. The intrinsic couplings of modes through their eigenfunctions can be described by coupling coefficients. Here, we concentrate on quadratic and cubic coupling coefficients that describe the nonlinear coupling of modes with itself and are called self-coupling coefficients.We considered radial and nonradial oscillation modes of polytropic models with degrees of central condensation that correspond to central condensations of main sequence stars to highly condensed evolved stars. We study the influence of the radial order and the degree of the oscillation mode on the self- coupling coefficients.

scholarly journals Oscillation mode linewidths and heights of 23 main-sequence stars observed byKepler

2014 ◽  
Vol 566 ◽  
pp. A20 ◽  
Author(s):  
T. Appourchaux ◽  
H. M. Antia ◽  
O. Benomar ◽  
T. L. Campante ◽  
G. R. Davies ◽  
...  
Keyword(s):  
Main Sequence ◽  
Oscillation Mode ◽  
Main Sequence Stars

scholarly journals TESS Giants Transiting Giants. I.: A Noninflated Hot Jupiter Orbiting a Massive Subgiant

2022 ◽  
Vol 163 (2) ◽  
pp. 53
Author(s):  
Nicholas Saunders ◽  
Samuel K. Grunblatt ◽  
Daniel Huber ◽  
Karen A. Collins ◽  
Eric L. N. Jensen ◽  
...  
Keyword(s):  
Main Sequence ◽  
Planetary System ◽  
Scattered Light ◽  
Image Data ◽  
Velocity Measurements ◽  
Main Sequence Stars ◽  
Transiting Planets ◽  
Depth Difference ◽  
Evolved Stars ◽  
Hot Jupiter

Abstract While the population of confirmed exoplanets continues to grow, the sample of confirmed transiting planets around evolved stars is still limited. We present the discovery and confirmation of a hot Jupiter orbiting TOI-2184 (TIC 176956893), a massive evolved subgiant (M ⋆ = 1.53 ± 0.12 M ⊙, R ⋆ = 2.90 ± 0.14 R ⊙) in the Transiting Exoplanet Survey Satellite (TESS) Southern Continuous Viewing Zone. The planet was flagged as a false positive by the TESS Quick-Look Pipeline due to periodic systematics introducing a spurious depth difference between even and odd transits. Using a new pipeline to remove background scattered light in TESS Full Frame Image data, we combine space-based TESS photometry, ground-based photometry, and ground-based radial velocity measurements to report a planet radius of R p = 1.017 ± 0.051 R J and mass of M p = 0.65 ± 0.16 M J . For a planet so close to its star, the mass and radius of TOI-2184b are unusually well matched to those of Jupiter. We find that the radius of TOI-2184b is smaller than theoretically predicted based on its mass and incident flux, providing a valuable new constraint on the timescale of post-main-sequence planet inflation. The discovery of TOI-2184b demonstrates the feasibility of detecting planets around faint (TESS magnitude > 12) post-main-sequence stars and suggests that many more similar systems are waiting to be detected in the TESS FFIs, whose confirmation may elucidate the final stages of planetary system evolution.

scholarly journals Oscillation mode linewidths and heights of 23 main-sequence stars observed byKepler(Corrigendum)

2016 ◽  
Vol 595 ◽  
pp. C2 ◽  
Author(s):  
T. Appourchaux ◽  
H. M. Antia ◽  
O. Benomar ◽  
T. L. Campante ◽  
G. R. Davies ◽  
...  
Keyword(s):  
Main Sequence ◽  
Oscillation Mode ◽  
Main Sequence Stars

scholarly journals Magnetic inhibition of convection in O-star envelopes

2019 ◽  
Vol 487 (3) ◽  
pp. 3904-3913 ◽  
Author(s):  
James MacDonald ◽  
Véronique Petit
Keyword(s):  
Magnetic Field ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Lower Field ◽  
Dipole Strength ◽  
Evolved Stars ◽  
Hydrostatic Balance ◽  
Stellar Envelopes ◽  
Stars Evolution ◽  
Good Agreement

ABSTRACT It has been suggested that the absence of macroturbulence in the atmosphere of NGC 1624−2 is due its strong magnetic field (the strongest known for a massive O star) suppressing convection in its outer layers, removing the mechanism thought responsible for the observed macroturbulence in stars with lower field strengths. Here, we develop and apply a criterion for a uniform magnetic field to suppress convection in stellar envelopes in which radiation pressure is a significant contributor to hydrostatic balance. We find upper mass limits of ∼55 and ∼30 M⊙ for magnetic suppression to be possible in zero-age main-sequence and terminal-age main-sequence stars, respectively. For evolved stars, magnetic suppression of convection can significantly alter the stars’ evolution. For NGC 1624−2, we find that a polar dipole strength of 16.5 ± 5.9 kG is required to suppress convection, in good agreement with the value ∼20 kG measured by spectropolarimetry.

scholarly journals Wind Properties of Young Stars

1987 ◽  
Vol 115 ◽  
pp. 398-398
Author(s):  
Nino Panagia
Keyword(s):  
Star Formation ◽  
Mass Loss ◽  
Main Sequence ◽  
Young Stars ◽  
Statistical Properties ◽  
Main Sequence Stars ◽  
Evolved Stars

The statistical properties of winds form young stars are summarized and discussed. One and the same mechanism, possibly related to the process of star formation, appears to be responsible for mass loss in all pre-main-sequence stars. Moreover, evidence is found that the ionization and the acceleration of the winds of very young stars are produced by processes different from those operating in main sequence and more evolved stars.

Nonlinear propagation of the ordinary mode in a hot magnetoplasma

1977 ◽  
Vol 18 (3) ◽  
pp. 433-449 ◽  
Author(s):  
Tu Khiet ◽  
Y. Furutani ◽  
Y. H. Ichikawa
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Kinetic Theory ◽  
The Self ◽  
Nonlinear Propagation ◽  
Ordinary Wave ◽  
Nonlinear Coupling ◽  
Zero Temperature ◽  
Coupling Coefficients ◽  
Maxwellian Plasma

Kinetic theory of the self-modulation of a quasi-monochromatic ordinary wave propagating across an external magnetic field is presented. Explicit expressions of the dispersion and the nonlinear coupling coefficients are given for a Maxwellian plasma. In the limit of zero-temperature, a Karpman–Kruskal linear stability of the O-mode envelope is discussed.

scholarly journals Fast and Automated Peak Bagging with DIAMONDS (FAMED)

2020 ◽  
Vol 640 ◽  
pp. A130
Author(s):  
E. Corsaro ◽  
J. M. McKeever ◽  
J. S. Kuszlewicz
Keyword(s):  
Main Sequence ◽  
Oscillation Mode ◽  
Asymptotic Giant Branch ◽  
Helium Burning ◽  
Mode Identification ◽  
Wide Range ◽  
Oscillation Modes ◽  
Red Giant ◽  
Stellar Properties ◽  
Subgiant Stars

Stars of low and intermediate mass that exhibit oscillations may show tens of detectable oscillation modes each. Oscillation modes are a powerful tool to constrain the internal structure and rotational dynamics of the star, hence allowing one to obtain an accurate stellar age. The tens of thousands of solar-like oscillators that have been discovered thus far are representative of the large diversity of fundamental stellar properties and evolutionary stages available. Because of the wide range of oscillation features that can be recognized in such stars, it is particularly challenging to properly characterize the oscillation modes in detail, especially in light of large stellar samples. Overcoming this issue requires an automated approach, which has to be fast, reliable, and flexible at the same time. In addition, this approach should not only be capable of extracting the oscillation mode properties of frequency, linewidth, and amplitude from stars in different evolutionary stages, but also able to assign a correct mode identification for each of the modes extracted. Here we present the new freely available pipeline FAMED (Fast and AutoMated pEak bagging with DIAMONDS), which is capable of performing an automated and detailed asteroseismic analysis in stars ranging from the main sequence up to the core-helium-burning phase of stellar evolution. This, therefore, includes subgiant stars, stars evolving along the red giant branch (RGB), and stars likely evolving toward the early asymptotic giant branch. In this paper, we additionally show how FAMED can detect rotation from dipolar oscillation modes in main sequence, subgiant, low-luminosity RGB, and core-helium-burning stars.

Chromospheric activity as a function of age in main-sequence stars

1966 ◽  
Vol 24 ◽  
pp. 40-43
Author(s):  
O. C. Wilson ◽  
A. Skumanich
Keyword(s):  
Main Sequence ◽  
The Sun ◽  
Main Sequence Stars ◽  
Tentative Conclusion ◽  
Chromospheric Activity ◽  
General Field ◽  
Large Clusters

Evidence previously presented by one of the authors (1) suggests strongly that chromospheric activity decreases with age in main sequence stars. This tentative conclusion rests principally upon a comparison of the members of large clusters (Hyades, Praesepe, Pleiades) with non-cluster objects in the general field, including the Sun. It is at least conceivable, however, that cluster and non-cluster stars might differ in some fundamental fashion which could influence the degree of chromospheric activity, and that the observed differences in chromospheric activity would then be attributable to the circumstances of stellar origin rather than to age.

On The Radii of Ap Stars

1976 ◽  
Vol 32 ◽  
pp. 49-55 ◽  
Author(s):  
F.A. Catalano ◽  
G. Strazzulla
Keyword(s):  
Observational Data ◽  
Line Width ◽  
Main Sequence ◽  
Main Sequence Stars ◽  
Ap Stars

SummaryFrom the analysis of the observational data of about 100 Ap stars, the radii have been computed under the assumption that Ap are main sequence stars. Radii range from 1.4 to 4.9 solar units. These values are all compatible with the Deutsch's period versus line-width relation.

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