Exocomets: A study of the gaseous environment of A-type main sequence stars

Isabel Rebollido Vázquez
2020 Zenodo  
In main sequence stars, infrared excesses attributed to the presence of circumstellar dust in debris discs has been the empirical indirect probe of the existence of minor bodies for more than 40 years, as they were needed to explain the dust emission. But it was not until 1987 that the first evidence of the presence of exocomets was found. It was around the Beta Pictoris star and it came with the detection of non-photospheric variable absorptions superimposed to the photospheric Ca II lines.
more » ... ce then, the number of known stars with exocomet-like absorptions has grown slowly, through sporadic works, up to ~20 stars, all of them A-type. The growth of the exoplanetary field, and the possible relevance of minor bodies in the configuration, building-up and architecture of planetary systems, have turned the attention of the scientific community again to the study of small bodies around stars other than the Sun. Encouraging are the first detections of exocometary bodies in photometric light curves from data taken by exoplanet search missions such as Kepler and TESS. Photometric detection using the exquisite light curves from these space observatories, in addition of providing a new methodology, has demonstrated that exocomets, as was expected from the early detection of infrared excesses, are present around stars of different spectral types in the main sequence. This thesis carries out a systematic spectroscopic survey in the time domain with the aim of detecting exocometary activity around main-sequence stars. The main objectives are, first, to enlarge the sample of known exocomet-host stars, and second, determine the possible environmental characteristics of the exocomet-host systems that could help to understand and detect them. A large survey to search for exocometary signals was conducted, where around 1500 high-resolution optical spectra of 117 stars with spectral types G to B were inspected. Although it was performed on a biase [...]
doi:10.5281/zenodo.3690841 fatcat:tpi3o47wgzf45p55oiqcw363oy