STScI Preprint #1331
Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, operated under NASA contract No. NAS5-26555
We report observations of dramatic morphological changes in the extremely young Herbig-Haro object ejected by the pre-main sequence binary XZ Tauri. Hubble Space Telescope images taken in 1995 showed a filled bubble of emission nebulosity extending 4" NNE of the system in the direction of a previously known jet. New images obtained in 1998 show that the bubble has undergone a remarkable transition into a limb-brightened structure as it continues its motion away from the binary. The new images suggest that we may be witnessing the initial formation of the post-shock cooling zone in a newly emerging HH bow shock system, probably accompanied by significant temporal evolution in the nebula's emission line spectrum.
2 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218
3 MS 183-900, Jet Propulsion Laboratory, Pasadena, CA 91109
4 Astrophysics Division, Space Science Department, European Space Agency
5 Dept. of Physics and Astronomy, Arizona State University, Tyler Mall, Tempe AZ 85287
6 Instituto de Astronomía, Universidad Nacional Autónoma de México, 58090 Morelia, Michoacan, Mexico
7 Dept. of Atmospheric, Oceanic, and Space Sciences, University of Michigan, 2455 Hayward, Ann Arbor, MI 48109
8 Dept. of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison WI 53706
9 Dept. of Physics, Carnegie-Mellon University, Wean Hall, 5000 Forbes Avenue, Pittsburgh, PA 15213
10 Dept. of Astronomy, New Mexico State University, Box 30001, Dept. 4500, Las Cruces NM 88003
11 Mt. Stromlo and Siding Springs Observatories, Australian National University, Weston Creek Post Office, ACT 2611 Australia