Hen 2-260 emission line fluxes

The planetary nebula shows a complex structure and possibly a bipolar outflow. The nebula is relatively dense and young. The central star is just starting O^+^ ionization (Teff~30000K).

Comparison of our observations with literature data indicates a 50% increase of the [OIII] 5007{AA} line flux between 2001 and 2012. We interpret it as the result of the progression of the ionization of O^+^. The central star evolves to higher temperatures at a rate of 45+/-7K/yr.

The heating rate is consistent with post-AGB evolutionary tracks for a final mass of 0.626^+0.003^_-0.005_M_{sun}_ or 0.645+/-0.008M_{sun}_ for two different sets of tracks from literature. The photometric monitoring of Hen 2-260 revealed non-periodic variations on a timescale of hours or days. There is no direct indication for central star binarity in the spectrum, nor for a strong stellar wind.

The variability may be caused by pulsations of the star. The temperature evolution of the central star can be traced using spectroscopic observations of the surrounding planetary nebula spanning a timescale of roughly a decade. This allows us for precise determination of the stellar mass, since the pace of the temperature evolution depends critically on the core mass.

The method is independent on the absolute age of the nebula. The kinematical age of the nebula is consistent with the age obtained from the evolutionary track. The final mass of the central star is close to the peak of the mass distribution for central stars of planetary nebulae found in other studies.

The object belongs to a group of young central stars of planetary nebulae showing photometric variability.