Physics
Scientific paper
Mar 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt.......269c&link_type=abstract
PhD Thesis, School of Cosmic Physics, Dublin Institute for Advanced Studies, 5 Merrion Square, Dublin 2, Ireland, 1994.
Physics
Scientific paper
Optical outflows, i.e. Herbig--Haro (HH) objects and jets, have only recently been found to be associated with high luminosity (> 50 Lodot) young stars, such as the Herbig Ae/Be stars. In this thesis, using deep narrow band CCD imaging, the regions about three Herbig Ae/Be stars, V380 Ori, LkHα 198 and V376 Cas, together with one high luminosity embedded infrared source, Cepheus A, have been examined in detail. In most cases, these young stellar objects have been known or have been suspected in the past to be associated with HH objects. However, each of these regions is found to be considerably more complex than previously thought with the detection of at least twenty new HH objects, many of which are examined spectroscopically. For LkHα 198, a companion star (LkHα 198B) is found 50722 to its northeast which drives its own optical outflow. A jet is also seen to emanate from LkHα 198 and the presence of these two outflows in close proximity, not only explains many of the existing observations such as polarimetric measurements, but also draws into question previous interpretations for the molecular outflow source and the presence of a far infrared halo about LkHα 198. For V376 Cas a number of nearby HH emission knots are reported, some of which may be associated. Perhaps one of the most remarkable discoveries is that of a HH ``loop'' to the east of Cepheus A. Taken together with the HH complex GGD 37 to the west of Cepheus A, it is argued that one observes here a bipolar poorly collimated wind, orientated East--West in the plane of the sky. A similar emission line ``loop'' structure is also observed to the west of V380 Ori and, while it is clear that this ``loop'' and the molecular outflow to the east delineate a bipolar poorly collimated wind, it is unclear whether the more distant components of the ``loop'' are HH or HII emission. Importantly, the presence of LiIλ6708 in the spectrum of V380 Ori, suggests that it is not a Herbig Ae/Be star but is in fact a T-Tauri star. The high luminosity of the star and the HH emission seen nearest to it, is taken as evidence of a variable poorly collimated wind which emanates from V380 Ori and is interacting with a cavity left over from some previous outburst. A poorly collimated HH component is also seen for LkHα 198 in addition to its jet, and using all the observations made here and those collected from existing data, it seems increasingly more obvious that optical outflows are more poorly collimated from higher rather than lower luminosity sources (e.g. the Classical T-Tauri stars).
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