Supervisor: Tappert, ClausInternal reviewer: Arcos, CatalinaExternal reviewer: Ederoclite, AlessandroCeledón Pichún, Lientur2026-01-222026-01-222025https://repositoriobibliotecas.uv.cl/handle/uvscl/17028Nova eruptions are a recurrent phenomenon in the lifetime of Cataclysmic Variables, playing a crucial role in their evolution. A classical nova eruption occurs on the sur- face of a white dwarf (WD) once a critical amount of hydrogen has been accreted, releasing a significant amount of energy during the process. As a consequence, the luminosity of the system increases significantly in a short amount of time before start- ing to fade slowly, originating what is known as a nova eruption light curve. An additional consequence of the nova eruption is the ejection of the accreted material into the interstellar medium, forming a nebular remnant around the system known as a nova shell. It has been widely assumed that the properties of these nova shells, such as their axial ratio, expansion velocity, and ejected mass, are directly correlated to the mass of the underlying WD. This makes nova shells excellent diagnostic tools for our understanding of the physical processes that dominate the ejection mechanisms during a nova eruption. The usual study of nova shells involves the use of narrow-band (NB) photometry and long-slit (LS) spectroscopy, which, when combined, can provide a precise, although incomplete, characterisation of the expanding shell. A better approach is to use integral-field spectroscopy, which gives a complete characterisation of the shell’s geometry and kinematics. In this thesis, for the first time, an in-depth analysis of nova shells using the Multi-Unit Spectrograph Explorer (MUSE), an integral-field spectrograph, is carried out. Data for a total of 21 nova shells with ages between 26 and 120 years have been collected over several observation cycles, allowing for the detection of a nova shell around 17 systems, yielding the largest sample of nova shells observed with MUSE to date. The analysis of the shells involves creating passband photometry from the datacube to address the shell geometry, creating channel and velocity maps to determine the kinematics of the ejecta, and combining this information to obtain the 3D geometry of the nova shell. The results emphasise the significant advantages that IFS observations have over the classical combination of NB images and LS spectroscopy. A firstcase that showcases this was the study of the old shell around RR Pic (Nova Pictoris1925), which was observed mainly in the Hα, Hβ, and [OIII] λ 5007 A˚lines. The images and kinematics confirmed that the shell is composed of an equatorial ring that contains ∼ 99% of the Hα flux, and the rest corresponds to filaments expanding in the polar direction. The 3D reconstruction of the shell shows that hydrogen and oxygen emissions occupy different spatial positions, revealing the differences in the gas density across the shell. Within the selected sample of nova shells, a small group shows asymmetric ejecta, which defies the usual ejection mechanisms in nova shells. The first of these asymmetric shells was discovered around V1425 Aql (Nova Aquila 1995). From the MUSE data, it was concluded that the hydrogen shell consists of an approximately spherical shell, while the asymmetric ejecta traced by the oxygen forbidden emission possesses an arc-shaped geometry that surrounds the hydrogen shell. The origin of the asymmetry in these shells is far from clear, but it may have significant implications for our understanding of the ejection mechanisms. In addition to the particular analysis of these two individual nova shells, the number of detected shells allows for a quantitative analysis of the data. For the 17 shells, Hα images were obtained from the datacube to study the geometry of their shells. An ellipse was fitted to each one to obtain the semi-major and semi-minor axes, from which the axial ratio of the shell can be derived. This parameter was compared against the white dwarf masses extracted from the literature. No correlation was found, likely due to the uncertainties involved in the determination of the masses. The results of this thesis have been published in two articles in a refereed journal, with a third one being planned for the near future. They highlight the advantages and capabilities for the study of nova shells using MUSE, encouraging the rest of the community to use similar instruments and techniques.enERUPCION DE ESTRELLASESPECTROSCOPIA ASTRONOMICATDOC