Kinematics of 1200 kilometer per second jets in He 3-1475

Spectroscopic observations of a proto-planetary nebula He 3-1475 with the S pace Telescope Imaging Spectrograph reveal the kinematics of its high-veloc ity (1200 km s(-1)) jets. The jets are formed at a large (0.15 pc) distance from its central star by collimation of an asymmetric stellar wind in a pa ir of conical shocks seen in Wide Field Planetary Camera 2 (WFPC2) images. The jets consist of several pairs of knots symmetrically distributed with r espect to the central star, with most knots exhibiting a head-tail morpholo gy. Large (up to 650 km s(-1)) radial velocity gradients are seen within th e knots on subarcsecond scales, with velocities decreasing from the knot he ads toward their trailing tails. These large velocity gradients are a sign of efficient deceleration of jets by a much slower bipolar outflow. The inc lination angle of the bipolar outflow is equal to 40 degrees, based on Dopp ler shifts of the scattered stellar H alpha line. Its velocity is equal to 140 km s(-1) at a distance of 0.23 pc from the star and increases monotonic ally with the radial distance from the star. A comparison of new WFPC2 [N I I] lambda 6584 images with older WFPC2 images reveals expansion of the jets . The measured jet proper motions in combination with their radial velociti es imply that He 3-1475 is a Galactic bulge star at a distance of 8 kpc, lo cated 800 pc above the Galactic plane. Its very high luminosity (25,000 L.) implies that He 3-1475 must be significantly more massive than a typical a symptotic giant branch star within the Galactic bulge, perhaps because of a past mass transfer and/or a merger event in an interacting binary system.