Navegação por Assunto "Stars: evolution"
Resultados 1-20 de 46
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2006 Whole Earth Telescope observations of GD358 : a new look at the prototype DBV
(2009) [Artigo de periódico]We report on the analysis of 436.1 hr of nearly continuous high-speed photometry on the pulsating DB white dwarf GD358 acquired with the Whole Earth Telescope (WET) during the 2006 international observing run, designated ... -
Age distribution of lmc clusters from their integrated ubv colors : history of star formation
(1995) [Artigo de periódico]In this paper we revise the relationship between ages and metallicities of LMC star clusters and their integrated UBV colors. The study stands on the catalog of UBV colors of the Large Magellanic Cloud (LMC) clusters by ... -
Analysis of cool DO-type white dwarfs from the Sloan Digital Sky Survey data release 10
(2014) [Artigo de periódico]We report on the identification of 22 new cool DO-type white dwarfs (WDs) detected in data release 10 (DR10) of the Sloan Digital Sky Survey (SDSS). Among them, we found one more member of the so-called hot-wind DO WDs, ... -
An empirical test of the theory of crystallization in stellar interiors
(1997) [Artigo de periódico]Our theoretical calculations indicate that the massive pulsating DA white dwarf, BPM 37093, has a crystallized ion interior. Our estimates for the crystallized mass fraction depend on our assumption for the interior ... -
An independent method for determining the age of the universe
(1987) [Artigo de periódico]The oldest white dwarf stars in the solar neighborhood are still observable, and their luminosity distribution can be used to determine directly the age of the Galactic disk and, somewhat less directly, the age of the ... -
Asteroseismological measurements on PG 1159-035, the prototype of the GW Virginis variable stars
(2008) [Artigo de periódico]Aims. An asteroseismological study of PG 1159−035, the prototype of the GW Vir variable stars, has been performed on the basis of detailed and full PG1159 evolutionary models presented by Miller Bertolami & Althaus (2006, ... -
Asteroseismological study of massive ZZ Ceti stars with fully evolutionary models
(2013) [Artigo de periódico]We present the first asteroseismological study for 42 massive ZZ Ceti stars based on a large set of fully evolutionary carbon–oxygen core DA white dwarf models characterized by a detailed and consistent chemical inner ... -
Asteroseismology of ZZ Ceti stars with full evolutionary white dwarf models : II. The impact of AGB thermal pulses on the asteroseismic inferences of ZZ Ceti stars
(2018) [Artigo de periódico]Context. The thermally pulsing phase on the asymptotic giant branch (TP-AGB) is the last nuclear burning phase experienced by most low- and intermediate-mass stars. During this phase, the outer chemical stratification above ... -
Asteroseismology of ZZ Ceti stars with fully evolutionary white dwarf models : I. the impact of the uncertainties from prior evolution on the period spectrum
(2017) [Artigo de periódico]Context. ZZ Ceti stars are pulsating white dwarfs with a carbon-oxygen core build up during the core helium burning and thermally pulsing Asymptotic Giant Branch phases. Through the interpretation of their pulsation periods ... -
Blue-violet spectral evolution of young magellanic cloud clusters
(1995) [Artigo de periódico]We study the integrated spectral evolution in the blue-violet range of 97 blue star clusters in the Magellanic Clouds, from those associated with gas emission to those as old as a few hundred Myr. Some clusters are dominated ... -
Carbon stars in lmc clusters revisited
(1996) [Artigo de periódico]Examining the available data for AGB stars in the Large Magellanic Cloud (LMC) clusters, we address the question about the mass interval of low- and intermediate-mass stars which eventually evolve into carbon stars (C ... -
A comparative analysis of the observed white dwarf cooling sequence from globular clusters
(2016) [Artigo de periódico]We report our study of features at the observed red end of the white dwarf cooling sequences for three Galactic globular clusters: NGC 6397, 47 Tucanae and M 4. We use deep colour– magnitude diagrams constructed from ... -
Comparing the asteroseismic properties of pulsating pre-extremely low mass white dwarf and δ Scuti stars
(2018) [Artigo de periódico]Context. Pulsating extremely low-mass pre-white dwarf stars (pre-ELMV), with masses between ~0.15 M⊙ and ~0.30 M⊙, constitute a new class of variable stars showing g- and possibly p-mode pulsations with periods between 320 ... -
Constraining the evolution of ZZ Ceti
(2003) [Artigo de periódico]We report our analysis of the stability of pulsation periods in the DAV star (pulsating hydrogen atmosphere white dwarf ) ZZ Ceti, also called R548. On the basis of observations that span 31 years, we conclude that the ... -
A detection of the evolutionary time scale of the da white dwarf G117-B15A with the Whole Earth Telescope
(1991) [Artigo de periódico]We have detected the time rate of change for the main pulsation period of the 13,000 K DA white dwarf G117-B15A, using the Whole Earth Telescope (WET). The observed rate of period change, P = (12.0 ± 3.5) x 10- 15 s s - ... -
Discovery of an ultramassive pulsating white dwarf
(2013) [Artigo de periódico]We announce the discovery of themostmassive pulsating hydrogen-atmosphere white dwarf (WD) ever discovered, GD 518. Model atmosphere fits to the optical spectrum of this star show it is a 12,030 ± 210 K WD with a log g = ... -
Effects of the 12C(α, γ) 16O reaction rates on single stellar evolution computations
(2022) [Tese]One of the largest uncertainties in stellar evolutionary computations is the accuracy of the considered reaction rates. The 12C(α, γ) 16O reaction is important in stars of all masses, but is of particular importance for ... -
Evidence of thin helium envelopes in PG 1159 stars
(2008) [Artigo de periódico]We present evidence that PG 1159 stars could harbor He-rich envelopes substantially thinner than those predicted by current evolutionary models with current estimates of mass loss, which may be attributable to an extensive ... -
Evolutionary timescale of the pulsating white dwarf G117-B15A : the most stable optical clock known
(2000) [Artigo de periódico]We observe G117-B15A, the most precise optical clock known, to measure the rate of change of the main pulsation period of this blue-edge DAV white dwarf. Even though the obtained value is only within 1 σ, P = (2.3±1.4) x ... -
Ground-based observation of ZZ Ceti stars and the discovery of four new variables
(2019) [Artigo de periódico]We perform ground-based photometric observations of 22 DA white dwarf stars, 10 already known ZZ Cetis and 12 candidates with atmospheric parameters inside the classical instability strip. We report on the discovery of ...
