Universität zu Köln

Ganci, Valerio (2024). Characterization of the inner regions of protoplanetary disks by spectro-interferometry. PhD thesis, Universität zu Köln.

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Abstract

The protoplanetary disks around YSOs have a key role in the still unclear processes of planet formation and evolution. However, their picture is not yet complete, especially with regards to their innermost regions, observed through long-baseline IR interferometry, required to probe sub-au scales. Particularly interesting are the YSOs belonging to the Herbig stars sub-group. With a stellar mass set to range between 2 and 12 solar masses, they are thought to be the bridge between the relatively well understood low mass pre-main-sequence stars and the still obscure high mass ones. In this work I study three different Herbig stars, each one of them being a benchmark for various open-ended questions on young stellar objects evolution and on the physical processes happening in their innermost circumstellar regions. The first is HD141569, a well-known Herbig star characterized by a transitional disk. GRAVITY detected a very faint dust emission in the first au of the system, previously thought to be dust-depleted. The system, despite his old age, shows a Br-gamma-line emission, for which the GRAVITY spectrum and differential phases suggest the emitting gas to lie in a Keplerian disk around the central star. Through the study of the second system, HD98922, a unique variability investigation of its innermost gas and dust material is presented. I suggest a way to bypass poor (u,v)-plane coverage and to assess variability through interferometric data geometrical modeling. The modeling suggests an orbiting, crescent, dusty feature, hinting to a dust-trap scenario at mas scale in the first au of the HD98922 circumstellar environment. A strongly time-variable Br-gamma-line emission is also observed, which follows at first order the orbital motion of the dusty feature. Lastly, the quadruple Herbig stars system HD52721 is studied and tested for interferometric binarity in au scales. A new companion is detected, as well as a complex and strongly time-variable Br-gamma-line emission.

Item Type:	Thesis (PhD thesis)
Creators:	Creators Email ORCID ORCID Put Code Ganci, Valerio ganci@ph1.uni-koeln.de UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-724118
Date:	2024
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Physics > Institute of Physics I
Subjects:	Natural sciences and mathematics Physics
Uncontrolled Keywords:	Keywords Language Protoplanetary disks English Infrared Interferometry English Young stellar objects English
Date of oral exam:	30 May 2023
Referee:	Name Academic Title Labadie, Lucas Univ.-Prof. Dr. Zensus, Anton Univ.-Prof. Dr.
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/72411