The Constant-Velocity Highly Collimated Outflows of the Planetary Nebula He 2-90

We present high-dispersion echelle spectroscopic observations and a narrowband [N II] image of the remarkable jetlike features of He 2-90. They are detected in the echelle spectra in the Hα and [N II] lines but not in other nebular lines. The [N II]/Hα ratio is uniformly high, ~=1. The observed kinematics reveals bipolar collimated outflows in the jetlike features and shows that the southeast (northwest) component expands toward (away from) the observer at a remarkably constant line-of-sight velocity, 26.0+/-0.5 km s^-1. The observed expansion velocity and the opening angle of the jetlike features are used to estimate an inclination angle of ~=5° with respect to the sky plane and a space expansion velocity of ~=290 km s^-1. The spectrum of the bright central nebula reveals a profusion of Fe lines and extended wings of the Hα line, similar to those seen in symbiotic stars and some young planetary nebulae that are presumed to host a mass-exchanging binary system. If this is the case for He 2-90, the constant velocity and direction of the jets require a very stable dynamic system against precession and warping.