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PRODID:https://murmitoyen.com/events/vanille/udem/
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UID:69dac290f1201
DTSTAMP:20260411T175216
DTSTART:20180201T113000
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URL:https://murmitoyen.com/events/vanille/udem/detail/806555-unveiling-the-
 internal-chemical-stratification-in-white-dwarf-stars
LOCATION:Pavillon Roger-Gaudry \, 2900\, boul. Édouard-Montpetit\, Local M
 -415\, Montréal\, QC\, Canada
SUMMARY:Unveiling the internal chemical stratification in white-dwarf stars
DESCRIPTION:Conférence présentée par Gilles Fontaine du Département de 
 physique de l'Université de Montréal\,
\nRésumé :White-dwarf stars rep
 resent the final products of the evolution of more than 95% of all stars\,
  and their internal constitution bears the imprints of several mechanisms 
 that occur during the previous phases of stellar evolution in general. In 
 particular\, it is expected that the internal chemical stratification of a
  typical white dwarf is shaped\, over time\, by the still uncertain rate o
 f the 12C(α\,γ)16O thermonuclear reaction\, by convection\, semi-convect
 ion\, overshooting\, other mixing processes such as rotational mixing\, an
 d by thermal pulses that occur primarily on the Asymptotic Giant Branch. A
 ll of these notoriously suffer from major uncertainties and are not secure
 ly modeled in current stellar evolution codes\, thus illustrating the nume
 rous shortcomings that still plague our treatments of the physics involved
 . Here we report the unraveling of the internal radial chemical stratifica
 tion (oxygen-carbon-helium) in the pulsating hydrogen-deficient white-dwar
 f star KIC08626021 on the basis of asteroseismic sounding and independentl
 y of stellar evolution calculations. Using a novel approach to describe an
 d test the chemical distribution inside the core and envelope of a pulsati
 ng white dwarf\, we uniquely recover a model whose theoretical pulsation p
 eriods match perfectly the high precision observations of that star obtain
 ed with the Kepler satellite. Our seismic calibration of the oxygen-carbon
 -helium internal stratification in a representative white-dwarf star impli
 es to revisit stellar evolution theory and its constitutive physics in the
  light of this new constraint. It also has repercussions on techniques usi
 ng white dwarfs to derive stellar population ages.
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TZID:America/Montreal
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