Herbig Ae/Be systems: stars, disks, and star-disk interactions

• Autores: Jorge Guzmán Díaz
• Directores de la Tesis: Ignacio Mendigutía Gómez (dir. tes.), Benjamín Montesinos Comino (dir. tes.)
• Lectura: En la Universidad Autónoma de Madrid ( España ) en 2024
• Idioma: inglés
• Número de páginas: 145
• Títulos paralelos:
  • Sistemas Herbig Ae/Be: estrellas, discos e interacciones estrella-disco
• Enlaces
  • Tesis en acceso abierto en: Biblos-e Archivo
• Resumen

  • Herbig Ae/Be stars (HAeBes) are pre-main sequence, intermediate mass objects surrounded by a protoplanetary disk. These stars exhibit crucial properties. First, HAeBes are the link between low-mass T Tauri stars and massive young stellar objects, so the knowledge of their physical properties bridge the gap between low- and high-mass star formation regimes. Second, HAeBes have large and bright disks, which make them excellent candidates for the use of high-resolution imaging techniques and the study of planetary formation. However, before the advent of Gaia, HAeBes were studied in small samples scattered on the sky, with their stellar and circumstellar parameters derived using different techniques. The aim of this thesis is to contribute to the knowledge of the HAeBe regime by the homogeneous characterization of a large sample of these stars. In particular, spectral energy distributions (SEDs) from the optical to the sub-millimeter range, synthetic models of photospheres and Gaia EDR3 parallaxes were used to estimate the stellar and circumstellar parameters of 209 bona fide HAeBes. From this sample, 67 HAeBes also have suitable spectra to carry out a metallicity analysis. The main results of this thesis are as follows: • The effective temperatures, visual extinctions, stellar radii, luminosities, masses and ages of the 209 HAeBes are provided, as well as circumstellar parameters such as mass accretion rates, disk masses and the sizes of the dust inner holes. The SED shapes have been also classified according to two different schemes associated with different disk properties. • The main mechanism driving disk dissipation in Herbig Be stars is likely photoevaporation, although other types of processes can not be ruled out (e.g., the presence of companions). In contrast, photoevaporation does not seem to be the dominant disk dissipation mechanism in Herbig Ae stars. • An online archive has been developed that collects all the parameters mentioned above, being updated as new HAeBes are discovered and characterized. • Stellar metallicities, surface gravities and projected rotational velocities have been derived for 67 HAeBes. • A correlation between metallicity and the shape of the SEDs is confirmed. In particular, HAeBes with low metallicities tend to have disks with cavities. Evidence is provided that these cavities are likely caused by the presence of giant planets. This work constitutes the most complete characterization of the stellar and circumstellar properties of HAeBes from SED analysis, providing unique constraints on their disk dissipation mechanisms and on the possible relation with planet formation