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54 results on '"Romero, Alejandra D."'

52. New cooling sequences for old hydrogen-rich white dwarfs

Author

Renedo, Isabel, primary, Althaus, Leandro G., additional, Córsico, Alejandro H., additional, Romero, Alejandra D., additional, Miller Bertolami, Marcelo M., additional, Rohrmann, René D., additional, García-Berro, Enrique, additional, Werner, Klaus, additional, and Rauch, T., additional

Published
2010
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53. New cooling sequences for old hydrogen-rich white dwarfs.

Author

Renedo, Isabel, Althaus, Leandro G., Córsico, Alejandro H., Romero, Alejandra D., Miller Bertolami, Marcelo M., Rohrmann, René D., and García-Berro, Enrique

Subjects
COOLING, WHITE dwarf stars, INTERSTELLAR hydrogen, AGE of stars, ASYMPTOTIC giant branch stars, STELLAR mass, NUCLEAR reactions, STELLAR evolution
Abstract

We present fully evolutionary white dwarf cooling tracks for hydrogen-rich DA white dwarfs. Our cooling sequences have been obtaind evolving white dwarf progenitors from the zero age main sequence, through the core hydrogen burning phase, the helium burning phase and the thermally pulsing asymptotic giant branch phase. Moreover, our evolutionary sequences are computed for a wide range of stellar masses and for two different metallicities: Z = 0.01 and Z = 0.001. The cooling sequences described here incorporate nuclear reactions during the early phases of white dwarf evolution, diffusion of the elements in the outer layers and, finally, all the relevant energy sources in the deep interior of the white dwarf, like the release of latent heat and the release of gravitational energy due to carbon-oxygen phase separation upon crystallization. We also provide colors and magnitudes for these sequences, computed using non-gray atmospheres, which include the Lyα quasi-molecular opacity. The calculations are extended down to an effective temperature of 2,500 K. [ABSTRACT FROM AUTHOR]

Published
2010
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54. Probing the Structure of Kepler ZZ Ceti Stars with Full Evolutionary Models-based Asteroseismology

Author

Gianninas, Hermes, Romero, Alejandra D., Kepler, Kawka, Koester, Córsico, Bonato, Gerónimo, F. C. De, Castanheira, and Althaus

Subjects
13. Climate action, 7. Clean energy
Abstract

We present an asteroseismological analysis of four ZZ Ceti stars observed with the Kepler spacecraft: GD 1212, SDSS J113655.17+040952.6, KIC 11911480, and KIC 4552982, based on a grid of full evolutionary models of DA white dwarf (WD) stars. We employ a grid of carbon-oxygen core models, characterized by a detailed and consistent chemical inner profile for the core and the envelope. In addition to the observed periods, we take into account other information from the observational data, such as amplitudes, rotational splittings, and period spacing, as well as photometry and spectroscopy. For each star, we present an asteroseismological model that closely reproduces their observed properties. The asteroseismological stellar mass and effective temperature of the target stars are (0.632 ± 0.027 M, 10737 ± 73 K) for GD 1212, (0.745 ± 0.007 M, 11110 ± 69 K) for KIC 4552982, (05480 ± 0.01 M, 12,721 ± 228 K) for KIC11911480, and (0.570 ± 0.01 M, 12,060 ± 300 K) for SDSS J113655.17+040952.6. In general, the asteroseismological values are in good agreement with the spectroscopy. For KIC 11911480 and SDSS J113655.17+040952.6 we derive a similar seismological mass, but the hydrogen envelope is an order of magnitude thinner for SDSS J113655.17+040952.6, which is part of a binary system and went through a common envelope phase.

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