Asteroseismic inferences from red-giant stars

Themeẞl, Nathalie

dc.contributor.advisor	Hekker, Saskia Dr.
dc.contributor.author	Themeẞl, Nathalie
dc.date.accessioned	2019-03-29T10:30:32Z
dc.date.available	2019-03-29T10:30:32Z
dc.date.issued	2019-03-29
dc.identifier.uri	http://hdl.handle.net/11858/00-1735-0000-002E-E5F1-E
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-7375
dc.identifier.uri	http://dx.doi.org/10.53846/goediss-7375
dc.language.iso	eng	de
dc.rights.uri	http://creativecommons.org/licenses/by-nc-nd/4.0/
dc.subject.ddc	530	de
dc.title	Asteroseismic inferences from red-giant stars	de
dc.type	doctoralThesis	de
dc.contributor.referee	Hekker, Saskia Dr.
dc.date.examination	2018-09-28
dc.subject.gok	Physik (PPN621336750)	de
dc.description.abstracteng	The analysis of high-precision long-term photometric time-series of data from the NASA Kepler space mission (2008 − 2012) has revolutionized the field of red-giant seismology. Solar-like oscillations could be detected in several thousands of pulsating red-giant stars that cover a wide range of stellar properties and different evolutionary stages. This thesis presents a dedicated study of oscillating red giants that belong to eclipsing binary systems (EBs) and open clusters. Through the study of stellar oscillation modes it is possible to draw inferences on the interior structure and evolution of stars, which is called asteroseismology. In the case of oscillating binary and cluster stars, the stellar parameters can be determined either by analysing the asteroseismic signal or through orbital analysis (EBs), and through stellar isochrones (clusters). The comparison between stellar parameters derived from independent analyses provides the means to test the reliability and accuracy of asteroseismic methods. The research presented in this thesis provides improvements to already existing asteroseismic concepts to allow high-precision asteroseismology. The first part of this thesis focuses on three oscillating red-giant components in EBs. Consistencies between the asteroseismic and dynamical stellar parameters using Kepler’s laws were found in cases where the asteroseismic methods accounted for the stellar mass, temperature, and metallicity dependence, as well as the so-called surface effect. The second part of this thesis discusses an asteroseismic ensemble study with the main objective of determining asteroseismic age estimates of about 60 oscillating red-giant stars that are members of the open clusters NGC 6791 and NGC 6819. Individual age determinations for the cluster giants led to a fairly large age span, although stars in open clusters are assumed to be coeval. The spread in the asteroseismic ages could be reduced by using the clusters’ metallicity from isochrone fitting as constraints for the asteroseismic modelling of the observed cluster giants. The global metallicity of the stars was shown to have a large impact on the age determinations. Improving the accuracy of this parameter would be helpful in obtaining more accurate asteroseismic ages. Among the stars that were targeted by Kepler for open cluster studies was a rare case of a Fourier power density spectrum showing solar-like oscillations of two red giants. The similar asteroseismic ages and masses of the two stars provided indications that they could be physically bound into a rare case of a multiple star system, while different distance estimates could point to an even rarer case of a chance alignment. This study is presented in the third part of this thesis.	de
dc.contributor.coReferee	Dreizler, Stefan Prof. Dr.
dc.subject.eng	asteroseismology	de
dc.subject.eng	red-giant stars	de
dc.subject.eng	data analysis	de
dc.subject.eng	eclipsing binary system	de
dc.subject.eng	open cluster	de
dc.subject.eng	solar-like oscillations	de
dc.subject.eng	stellar interior	de
dc.subject.eng	stellar evolution	de
dc.subject.eng	photometric time series of data	de
dc.subject.eng	stellar fundamental parameters	de
dc.subject.eng	binary analysis	de
dc.subject.eng	isochrone fitting	de
dc.subject.eng	stellar modelling	de
dc.subject.eng	global oscillation parameters	de
dc.subject.eng	asteroseismic scaling relations	de
dc.subject.eng	grid-based modelling	de
dc.subject.eng	Gaia distances	de
dc.subject.eng	ground-based photometry	de
dc.subject.eng	ground-based spectroscopy	de
dc.subject.eng	Kepler space mission	de
dc.subject.eng	power density spectrum	de
dc.subject.eng	ensemble study	de
dc.subject.eng	light curve analysis	de
dc.identifier.urn	urn:nbn:de:gbv:7-11858/00-1735-0000-002E-E5F1-E-8
dc.affiliation.institute	Fakultät für Physik	de
dc.identifier.ppn	1666649805

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