We present a study of the optical spectrum of the fascinating B [ e ] star Hen 2-90 based on new high-resolution observations taken with FEROS at the ESO 1.52m telescope in La Silla ( Chile ) .
The recent HST image of Hen 2-90 ( Sahai et al . 2002 ) reveals a bipolar , highly ionized region , a neutral disk-like structure seen almost perfectly edge-on , and an intermediate region of moderate ionization .
The slits of our observations cover the same innermost region of Hen 2-90 as the HST image , which allows us to combine the observations .
Our spectra contain a huge amount of permitted and forbidden emission lines of atoms in different stages of ionization .
In addition , the line wings deliver velocity information of the emitting region .
We find correlation between the different ionization states of the elements and the velocities derived from the line profiles : the highly ionized atoms have the highest outflow velocity , while the neutral lines have the lowest .
When combining the velocity information with the HST image of Hen 2-90 , it seems that a non-spherical stellar wind model is a good option to explain the ionization and spatial distribution of the circumstellar material .
Our modeling of the forbidden emission lines results in strong evidence for Hen 2-90 being a compact planetary nebulae that has undergone a superwind phase of high , non-spherical mass loss , most probably triggered by a central star that was rotating with about 80 % of the critical velocity .
We find a total mass loss rate during this superwind phase on the order of 3 \times 10 ^ { -5 } M _ { \odot } yr ^ { -1 } .