Pulsating white dwarfs: new insights

CÓRSICO, A.H.; ALTHAUS, L. G.; MILLER BERTOLAMI, M. M.; KEPLER, S O

ASTRONOMY AND ASTROPHYSICS REVIEW

SPRINGER

Lugar: Berlin; Año: 2019 vol. 27 p. 7 - 7

0935-4956

Stars are extremely important astronomical objects that constitute the pillars on whichthe Universe is built, and as such, their study has gained increasing interest overthe years. White dwarf stars are not the exception. Indeed, these stars constitute thefinal evolutionary stage for more than 95% of all stars. The Galactic population ofwhite dwarfs conveys a wealth of information about several fundamental issues andare of vital importance to study the structure, evolution and chemical enrichment ofour Galaxy and its components?including the star formation history of the MilkyWay. Several important studies have emphasized the advantage of using white dwarfsas reliable clocks to date a variety of stellar populations in the solar neighborhoodand in the nearest stellar clusters, including the thin and thick disks, the Galacticspheroid and the system of globular and open clusters. In addition, white dwarfs aretracers of the evolution of planetary systems along several phases of stellar evolution.Not less relevant than these applications, the study of matter at high densities hasbenefitedfrom our detailedknowledgeabout evolutionaryandobservational propertiesof white dwarfs. In this sense, white dwarfs are used as laboratories for astro-particlephysics, being their interest focused on physics beyond the standard model, that is,neutrino physics, axion physics and also radiation from ?extra dimensions?, and even crystallization. The last decade has witnessed a great progress in the study of whitedwarfs. In particular, a wealth of information of these stars from different surveys hasallowed us to make meaningful comparison of evolutionary models with observations.While some information like surface chemical composition, temperature and gravity ofisolated white dwarfs can be inferred from spectroscopy, and the total mass and radiuscan be derived as well when they are in binaries, the internal structure of these compactstars can be unveiled only by means of asteroseismology, an approach based on thecomparison between the observed pulsation periods of variable stars and the periodspredicted by appropriate theoretical models. The asteroseismological techniques allowus to infer details of the internal chemical stratification, the total mass, and even thestellar rotation profile. In this review, we first revise the evolutionary channels currentlyaccepted that lead to the formation of white-dwarf stars, and then, we give a detailedaccount of the different sub-types of pulsating white dwarfs known so far, emphasizingthe recent observational and theoretical advancements in the study of these fascinatingvariable stars.