The Ultramassive White Dwarfs of the Alpha Persei Cluster
  We searched through the entire Gaia EDR3 candidate white dwarf catalogue for
stars with proper motions and positions that are consistent with the stars
having escaped from the Alpha Persei cluster within the past 81~Myr, the age of
the cluster. In this search we found five candidate white dwarf escapees from
Alpha Persei and obtained spectra for all five. We confirm that three are
massive white dwarfs sufficiently young to have originated in the cluster. All
three are more massive than any white dwarf previously associated with a
cluster using Gaia astrometry, and possess some of the most massive
progenitors. In particular, the white dwarf Gaia~EDR3~4395978097863572, which
lies within 25~pc of the cluster centre, has a mass of about 1.20 solar masses
and evolved from an 8.5 solar-mass star, pushing the upper limit for white
dwarf formation from a single massive star, while still leaving a substantial
gap between the resulting white dwarf mass and the Chandrasekhar mass.
