The impact of pre-white dwarf evolution on the pulsational properties and asteroseismological inferences of ZZ Ceti stars

ALTHAUS, LEANDRO GABRIEL; SOUZA OLIVEIRA, KEPLER; CÓRSICO, ALEJANDRO HUGO; DE GERÓNIMO, FRANCISCO CÉSAR; ROMERO, ALEJANDRA DANIELA

Austin, Texas

Conferencia; 21st European Workshop on White Dwarfs; 2018

The University of Texas at Austin

ZZ Ceti stars are pulsating white dwarfs with acarbon-oxygen core (or possibly ONe for the mostmassive stars) build up during the core heliumburning (CHeB) and thermally pulsing AsymptoticGiant Branch (TP-AGB) phases. Through the interpretationof their pulsation periods by means of asteroseismology,details about their origin and evolutioncan be inferred. The whole pulsation spectrumexhibited by ZZ Ceti stars strongly dependon the inner chemical structure. At present, thereare several processes affecting the chemical profilesthat are still not accurately determined. Wepresent a study of the impact of current uncertaintiesin the evolution of white dwarf progenitor onthe expected pulsation properties and on the stellarparameters inferred from asteroseismologicalfits of ZZ Ceti stars. Our analysis is based on aset of carbon-oxygen core white dwarf models thatare derived from full evolutionary computationsfrom the ZAMS to the ZZ Ceti domain. We consideredmodels in which we varied the number ofthermal pulses, the amount of overshooting, andthe carbon-alpha reaction rate within their uncertainties.We explore the impact of these major uncertaintiesin prior evolution on the chemical structureand expected pulsation spectrum. We find thatthese uncertainties yield significant changes in theg-mode pulsation periods being those found duringthe TP-AGB phase the most relevant for the pulsationalproperties and the asteroseismological derivedstellar parameters of ZZ Ceti stars. We concludethat the uncertainties in the white dwarf progenitorevolution should be taken into account indetailed asteroseismological analyses of these pulsatingstars.