An Evolutionary Sequence for Herbig Ae/Be Stars Based on UV Data

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Session 121 -- Early Stars, X-Ray Binaries, Theory
Oral presentation, Thursday, 12, 1995, 2:00pm - 3:30pm

[121.01D] An Evolutionary Sequence for Herbig Ae/Be Stars Based on UV Data

JMS Silvis (Catholic University of America)

This work represents a systematic study of the differences found in the UV spectra of 37 Herbig Ae/Be stars, involving over 800 spectra. By examining spectral and continuum differences between the members of this set of stars it is possible to construct an evolutionary sequence. This evolutionary sequence is supported by data from other bandpasses. Furthermore, there is a radical shift in the physics between the young systems and the more evolved systems.

The younger systems ( designated as UV Broad Line stars) are characterized by jets, pronounced reddening and large bands of absorption that arise from metastable states of Fe II. The more evolved systems (designated as UV Broad Line stars) show no indication of jets, considerably less absorption arising from metastsable states of Fe II and extremely strong shocks. These two groups can be dramatically illustrated by plotting Fe II equivalent width vs C IV equivalent width. In the Fe II / C IV plane the stars form a definite "L" shape. By placing a star in the "L" diagram, it is possible to predict characteristics in the IR, visible and radio bandpasses.

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