Asteroseismology of ultra-massive white dwarfs: New results from a multi-telescope survey

Ultra-massive white dwarfs (UMWDs) are key astrophysical laboratories, potentially composing oxygen-neon (ONe) or carbon-oxygen (CO) cores, depending on the evolutionary history of their progenitor stars. These compact remnants provide a unique window into a wide range of physical phenomena, including the final stages of stellar mergers, the crystallization process in dense matter, and the progenitors of Type Ia supernovae. To explore their internal structure, we have initiated an ambitious photometric survey aimed at discovering new pulsating UMWDs and probing their interiors through asteroseismology. This campaign utilizes a coordinated multi-telescope strategy involving HiPERCAM on the Gran Telescopio Canarias, GMOS on Gemini, and the ARC 3.5-meter telescope at Apache Point Observatory. In this talk, I will review our recent findings and present a detailed asteroseismological analysis of pulsating ultra-massive white dwarfs.