* Astronomy

Freinage important de la rotation d'étoiles avant leur stade de naine blanche
Une équipe internationale conduite par un chercheur CNRS du Laboratoire d'Astrophysique Toulouse-Tarbes (LATT : INSU-CNRS, Université Toulouse 3) a effectué le sondage d'une étoile en fin de vie, la naine blanche GW Virginis, en utilisant l'astérosismologie. Les chercheurs démontrent que cette étoile tourne sur elle-même très lentement dans ses régions internes. Cette étoile, à l'origine de type solaire, a donc connu une importante phase de freinage de sa rotation avant d'arriver à son stade final de naine blanche. Ce résultat est publié dans Nature du 24/09/2009.

Read more (French)

Title: Seismic evidence for the loss of stellar angular momentum before the white-dwarf stage
Authors: S. Charpinet, G. Fontaine & P. Brassard

White-dwarf stars represent the final products of the evolution of some 95% of all stars. If stars were to keep their angular momentum throughout their evolution, their white-dwarf descendants, owing to their compact nature, should all rotate relatively rapidly, with typical periods of the order of a few seconds. Observations of their photospheres show, in contrast, that they rotate much more slowly, with periods ranging from hours to tens of years. It is not known, however, whether a white dwarf could 'hide' some of its original angular momentum below the superficial layers, perhaps spinning much more rapidly inside than at its surface. Here we report a determination of the internal rotation profile of a white dwarf using a method based on asteroseismology. We show that the pulsating white dwarf PG 1159-035 rotates as a solid body (encompassing more than 97.5% of its mass) with the relatively long period of 33.61 ± 0.59 h. This implies that it has lost essentially all of its angular momentum, thus favouring theories which suggest important angular momentum transfer and loss in evolutionary phases before the white-dwarf stage.

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