Sakurai's object - A possible final helium flash in a planetary nebula nucleus

UBT/RIJK photometry and optical spectroscopy of Sakurai's object and direct imaging of the surrounding nebulosity are presented. The progenitor star is identified as a faint blue object of m(i) = 21. The circular planetary nebula has a diameter of 32'', its distance, derived from the HP Aux, is 5.5 kpc. At present, the object is a luminous supergiant of approximate spectral type F2, having M(V) = -4.1, and has clear indications of hydrogen underabundance, with carbon and oxygen overabundance. [ts photospheric radial velocity is the same as that of the surrounding planetary nebula, indicating that they are associated, and that there is currently no mass loss by a thick wind. A marginal IR excess suggests the presence of some hot dust.