Search

Your search keyword '"Córsico, A. H."' showing total 468 results
Start Over Author "Córsico, A. H."
468 results on '"Córsico, A. H."'

252. 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
Full Text
View/download PDF

254. The white dwarf cooling age of NGC 6791

Author

García-Berro, Enrique, primary, Althaus, Leandro G., additional, Torres, Santiago, additional, Lorén-Aguilar, Pablo, additional, Renedo, Isabel, additional, Córsico, Alejandro H., additional, Isern, Jordi, additional, Salaris, Maurizio, additional, Rohrmann, René D., additional, Werner, Klaus, additional, and Rauch, T., additional

Published
2010
Full Text
View/download PDF

271. The pulsation modes of the pre-white dwarf PG 1159-035

Author

Costa, J. E. S., primary, Kepler, S. O., additional, Winget, D. E., additional, O'Brien, M. S., additional, Kawaler, S. D., additional, Costa, A. F. M., additional, Giovannini, O., additional, Kanaan, A., additional, Mukadam, A. S., additional, Mullally, F., additional, Nitta, A., additional, Provençal, J. L., additional, Shipman, H., additional, Wood, M. A., additional, Ahrens, T. J., additional, Grauer, A., additional, Kilic, M., additional, Bradley, P. A., additional, Sekiguchi, K., additional, Crowe, R., additional, Jiang, X. J., additional, Sullivan, D., additional, Sullivan, T., additional, Rosen, R., additional, Clemens, J. C., additional, Janulis, R., additional, O'Donoghue, D., additional, Ogloza, W., additional, Baran, A., additional, Silvotti, R., additional, Marinoni, S., additional, Vauclair, G., additional, Dolez, N., additional, Chevreton, M., additional, Dreizler, S., additional, Schuh, S., additional, Deetjen, J., additional, Nagel, T., additional, Solheim, J.-E., additional, Gonzalez Perez, J. M., additional, Ulla, A., additional, Barstow, M., additional, Burleigh, M., additional, Good, S., additional, Metcalfe, T. S., additional, Kim, S.-L., additional, Lee, H., additional, Sergeev, A., additional, Akan, M. C., additional, Çakırlı, Ö., additional, Paparo, M., additional, Viraghalmy, G., additional, Ashoka, B. N., additional, Handler, G., additional, Hürkal, Ö., additional, Johannessen, F., additional, Kleinman, S. J., additional, Kalytis, R., additional, Krzesinski, J., additional, Klumpe, E., additional, Larrison, J., additional, Lawrence, T., additional, Meištas, E., additional, Martinez, P., additional, Nather, R. E., additional, Fu, J.-N., additional, Pakštienė, E., additional, Romero-Colmenero, E., additional, Riddle, R., additional, Seetha, S., additional, Silvestri, N. M., additional, Vučković, M., additional, Warner, B., additional, Zola, S., additional, Althaus, L. G., additional, Córsico, A. H., additional, and Montgomery, M. H., additional

Published
2007
Full Text
View/download PDF

281. Pulsations driven by the ϵ-mechanism in post-merger remnants: First results.

Author

Miller Bertolami, M. M., Córsico, A. H., Zhang, X., Althaus, L. G., and Jeffery, C. S.

Subjects
*STELLAR oscillations, *DWARF stars, *HELIUM, *GALAXIES, *ASTRONOMY
Abstract

Helium-rich subdwarfs are a rare subclass of hot subdwarf stars which constitute a small and inhomogeneous group showing varying degrees of helium enrichment. Only one star, LS IV °14 116 has been found to show multiperiodic luminosity variations. The variability of LS IV °14 116 has been explained as the consequence of nonradial g-mode oscillations, whose excitation is difficult to understand within the frame of the standard κ-mechanism driving pulsations in sdBV stars. In a recent study, we have proposed that the pulsations of LS IV °14 116 might be driven through the ϵ-mechanism acting in unstable Heburning zones in the interior of the star, that appear before the quiescent He-burning phase. One of the few accepted scenarios for the formation of He-rich subdwarfs is the merger of two He-core white dwarfs. As part of this project, we present a study of the ϵ-mechanism in post-merger remnants, and discuss the results in the light of the pulsations exhibited by LS IV °14 116. [ABSTRACT FROM AUTHOR]

Published
2013
Full Text
View/download PDF

291. Exploring the internal rotation of GW Vir stars through asteroseismology.

Author

Córsico, Alejandro H. and Althaus, Leandro G.

Subjects
*STELLAR rotation, *ASTEROSEISMOLOGY, *PULSATING stars, *HARMONIC analysis (Mathematics), *RIGID bodies, *SPHERICAL astronomy, *SYMMETRY (Physics), *WHITE dwarf stars
Abstract

Stellar rotation breaks the spherical symmetry of a star, and in the case of a pulsating star, it removes the intrinsic mode degeneracy of a nonradial g-mode characterized by an harmonic degree ℓ and a radial order κ. As a result, each pulsation frequency is split into multiplets of frequencies specified by different values of the azimuthal index m. Here, we explore the potential of asteroseismology to place constraints on the internal rotation of pulsating PG1159 stars, also known as GW Vir variables. We employ dedicated seismological models for the pulsating PG1159 stars PG 0122+200, PG 1159-035, and RX J2117+3412 in order to accurately assess the expected frequency splittings induced by rotation, and compare them with the observed ones. To this end, we assume different types of very simplified internal rotation profiles. We found that while PG 1159-035 definitely rotates as a rigid body, PG 0122+200 and RX J2117+3412 appear to be spinning with a rotation rate that depends on the depth. [ABSTRACT FROM AUTHOR]

Published
2010
Full Text
View/download PDF

292. The white dwarf cooling age of NGC 6791.

Author

García-Berro, Enrique, Althaus, Leandro G., Torres, Santiago, Lorén-Aguilar, Pablo, Renedo, Isabel, Córsico, Alejandro H., Isern, Jordi, Salaris, Maurizio, and Rohrmann, René D.

Subjects
WHITE dwarf stars, COOLING, AGE of stars, STELLAR luminosity function, STAR observations, OPEN clusters of stars, CRYSTALLIZATION
Abstract

NGC 6791 is a metal-rich ([Fe/H] = +0.4), well populated (∼3,000 stars) and nearby (m-M = 13.44mag) open cluster that has been imaged down to luminosities below those of the faintest white dwarfs, allowing us to obtain a reliable white dwarf luminosity function. The main-sequence turn-off age (∼8 Gyr) and the age derived from the termination of the white dwarf cooling sequence (∼6 Gyr) are very different. One possible explanation is that as white dwarfs cool, one of the ashes of helium burning, 22Ne, sinks in the deep interior of these stars. At lower temperatures, white dwarfs are expected to crystallize and phase separation of 12C and 16O is expected to occur. This sequence of events is expected to introduce significant delays in the cooling times. Using the white dwarf luminosity function of the metal-rich galactic cluster NGC 6791, we present the first solid observational evidence that indeed both gravitational sedimentation and phase separation upon crystallization occur in white dwarfs. [ABSTRACT FROM AUTHOR]

Published
2010
Full Text
View/download PDF

293. 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
Full Text
View/download PDF

300. The gravitational wave radiation of pulsating white dwarfs.

Author

Lorén-Aguilar, P., Isern, J., Althaus, L. G., Córsico, A. H., Lobo, J. A., and García-Berro, E.

Subjects
WHITE dwarf stars, GRAVITATIONAL waves, GENERAL relativity (Physics), GRAVITATION, ASTROPHYSICS
Abstract

We compute the emission of gravitational radiation from pulsating white dwarfs. This is done for a standard 0.6M⊙ white dwarf with a liquid CO core and a H-rich envelope, for a massive DA white dwarf with a partially crystallized core for which various l = 2 modes have been observed (BPM 37093) and for PG 1159-035 for which several quadrupole modes have been observed as well. We find that these stars do not radiate sizeable amounts of gravitational waves through their observed g-modes. We also explore the possibility of detecting gravitational waves radiated by the f-mode and the p-modes. We find that in this case the gravitational wave signal is very large. We also discuss the possible implications for the detection of gravitational waves from pulsating white dwarfs within the framework of future space-borne interferometers like LISA. © 2006 American Institute of Physics [ABSTRACT FROM AUTHOR]

Published
2006
Full Text
View/download PDF

Catalog

Books, media, physical & digital resources
See catalog results