Wyniki wyszukiwania - BazTech

Ograniczanie wyników

3 Acta Astronomica

Znaleziono wyników: 3

Liczba wyników na stronie

Wyniki wyszukiwania

Wyszukiwano:
w słowach kluczowych: stars: interiors

Sortuj według:

Ogranicz wyniki do:

Sounding Interiors of Four Pulsating Subdwarf B Stars with Stellar Pulsations

Baran A., Sanjayan S.

Acta Astronomica

2023

Vol. 73, No. 1

21--34

We present the results of asteroseismic modeling of four pulsating sdB stars KIC 2438324, KIC 2569576, KIC 2991403 and KIC 11159657. We used fully evolutionary models and this is the first attempt of seismic modeling of sdB stars using the MESA models and GYRE. We adopted an already reported list of periods identified with dipole modes. Additionally, we used two spectroscopic parameters, i.e., Teff and log g, and, only for KIC 2438324 and KIC 2569576, we used cluster parameters, i.e., total age and metallicity, to further filter the outcome of matching observed and theoretical pulsation periods. In the case of a spectroscopically constrained approach we derived a unique solution only for KIC 2438324. For two stars we derived unique input parameters except for the hydrogen and progenitor mass, respectively for KIC 2569576 and KIC 2991403. All input parameters except for the convective core and progenitor masses are unique for KIC 11179657. Except for KIC 11179657, our fits, measured by a relative period difference (ΔP/P), are well within 1%. These results sound very promising and more asteroseismic modeling of sdB stars should be done in future.

Ground-Based Observations of the ZZ Ceti Star HS~1625+1231

Kalup Cs., Bognár Zs., Sódor Á.

Acta Astronomica

2021

Vol. 71, No. 4

281--295

We present the results of our detailed light curve analysis of the ZZ Ceti star HS 1625+1231. We collected photometric time series data at Konkoly Observatory on 14 nights, and performed Fourier analysis of these data sets. We detected 11 significant frequencies, where six of them are found to be independent pulsation modes in the 514-881 s period range. By utilizing these frequencies, we performed preliminary asteroseismic investigations to give constraints on the main physical parameters, and to derive seismic distances for the star. Finally, we compared the astrometric distance provided by the Gaia EDR3 data with those seismic distances. Our selected model, considering both the spectroscopic measurements and the distance value provided by Gaia, has Teff=11 000 K and M*=0.60 M☉.

Nonradial Modes in RR Lyr Stars

Dziembowski W. A., Cassisi S.

Acta Astronomica

1999

Vol. 49, No. 3

371--382

We present a survey of nonradial mode properties in evolutionary sequences of RR Lyr star models. Attention is focused on the modes that may be driven by the opacity mechanism and on those that may be excited as a consequence of the 1:1 resonance with the radial pulsation. Qualitatively, all the models share the same properties of nonradial modes. At the quantitative level, the properties are to a large extent determined by the radial mode periods. There is only weak dependence on the star metallicity and no apparent dependence on the evolutionary status, that is on the helium exhaustion in the convective core. In the whole range of RRab and RRc star parameters we find unstable nonradial modes driven by the opacity mechanism. An instability of radial pulsation to a resonant excitation of nonradial oscillations is also a common phenomenon in both types. We discuss a possible role of nonradial modes in amplitude modulation observed in certain RR Lyr stars.