<> "The repository administrator has not yet configured an RDF license."^^ . <> . . "Characterization of stellar and sub-stellar atmospheres"^^ . "In this work I aim characterize a number of (sub)-stellar companions. When studying isolated brown\r\ndwarfs, very low-mass stars, and directly imaged exoplanets with insignificant orbital motion, we have to\r\nrely on theoretical models to determine basic parameters such as mass, age, and consequently, effective\r\ntemperature and surface gravity. While stellar and atmospheric models are rapidly evolving, we need a\r\npowerful tool to test and calibrate them.\r\nOne way to test models is to compare theoretical isochrones produced by interior and atmospheric models\r\nwith observed sequences in open clusters. Open clusters contain many objects of the same chemical\r\ncomposition and age, and spanning a range of masses. Using our own Lucky imaging observations and\r\nliterature data, I constructed a single-star sequence for the Hyades open cluster. I compare the obtained\r\nsequence to a set of theoretical isochrones identifying systematic offsets and revealing probable issues in\r\nthe models.\r\nHowever, there are many cases when it is impossible to test models before applying them to observations.\r\nOne example is applying atmospheric models for constraining parameters of the coolest known Y dwarf\r\nWISE 0855-07. I demonstrate the limits of constraining effective temperature and the presence/absence\r\nof water clouds that are introduced by unknown systematic effects in models and observations.\r\nIn the final chapter I introduce a novel method to take into account the above-mentioned systematics.\r\nI construct a ”systematics vector” that allows us to reveal problematic wavelength ranges when fitting\r\natmospheric models to observed near-infrared spectra of brown dwarfs and directly imaged exoplanets.\r\nThis approach plays a crucial role when retrieving abundances of brown dwarfs and exoplanets, in particularly,\r\na C/O ratio. The latter parameter is an important key to formation scenarios of brown dwarf and\r\nexoplanets. I show the way of constraining this parameter while eliminating systematics effects, which\r\nsignificantly improves the reliability of a final result and our conclusions about formation history of certain\r\nexoplanets and brown dwarfs."^^ . "2016" . . . . . . . "Taisiya G."^^ . "Kopytova"^^ . "Taisiya G. Kopytova"^^ . . . . . . "Characterization of stellar and sub-stellar atmospheres (PDF)"^^ . . . "thesis_kopytova_fin.pdf"^^ . . . "Characterization of stellar and sub-stellar atmospheres (Other)"^^ . . . . . . "lightbox.jpg"^^ . . . "Characterization of stellar and sub-stellar atmospheres (Other)"^^ . . . . . . "preview.jpg"^^ . . . "Characterization of stellar and sub-stellar atmospheres (Other)"^^ . . . . . . "medium.jpg"^^ . . . "Characterization of stellar and sub-stellar atmospheres (Other)"^^ . . . . . . "small.jpg"^^ . . . "Characterization of stellar and sub-stellar atmospheres (Other)"^^ . . . . . . "indexcodes.txt"^^ . . "HTML Summary of #21903 \n\nCharacterization of stellar and sub-stellar atmospheres\n\n" . "text/html" . . . "520 Astronomie"@de . "520 Astronomy and allied sciences"@en . . . "530 Physik"@de . "530 Physics"@en . .