  The 30 year orbit of the Cepheid Polaris has been followed with observations
by the
  CHARA Array (Center for High Angular Resolution Astronomy) from 2016 through
  2021. An additional
  measurement has been made with speckle interferometry at the Apache Point
Observatory.
  Detection of the companion is complicated
  by its comparative faintness--an extreme flux ratio. Angular diameter
  measurements appear to show some variation with pulsation phase.
  Astrometric positions of the companion were measured with a custom grid-based
model-fitting procedure and confirmed with the
  CANDID software. These positions were combined with the extensive radial
velocities
  discussed by Torres (2023) to fit an orbit. Because of the imbalance of the
sizes
  of the astrometry and radial velocity datasets, several methods of weighting
  are discussed. The resulting mass of the Cepheid
  is 5.13$\pm$ 0.28 $M_\odot$.
  Because of the comparatively large eccentricity of the orbit (0.63), the mass
derived
  is sensitive to the value found for the eccentricity.
  The mass combined with the distance shows that the Cepheid
  is more luminous than predicted for this mass from evolutionary tracks.
  The identification
  of surface spots is discussed. This would give credence to the identification
of
  photometric variation with a period of approximately 120 days as a rotation
period.
  Polaris has some unusual properties (rapid period change, a phase jump,
  variable amplitude, unusual polarization). However, a
  pulsation scenario involving pulsation mode,
  orbital periastron passage (Torres 2023), and low pulsation amplitude can
explain
  these characteristics within the framework of pulsation seen in Cepheids.
