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Session 106 - Herbig Ae/Be Stars.
Display session, Thursday, January 18
North Banquet Hall, Convention Center

[106.01] Circumstellar Material and Bipolar Outflow in Herbig Ae/Be Objects

J. M. S. Silvis, F. C. Bruhweiler (Catholic University of America)

In a previous study of 35 Herbig Ae/Be stars in the UV using IUE data, we proposed an evolutionary model for the circumstellar material around these systems. This work concluded that the strength of the absorption features arising from metastable states of Fe II indicate the evolutionary status of the circumstellar material. In short, young systems with large differential extinction and strong IR emission, consistent with a toroid, also show large equivalent widths from features arising from Fe II. In contrast, systems that are considered dustless show essentially no Fe II absorption. This implies an absorption feature arising from a metastable state of Fe II (such as UV 44) can be used to gauge the evolutionary status of the circumstellar shell.

Our results show that bipolar outflow is only seen in systems with large Fe II equivalent widths. Furthermore Ly-\alpha emission, which may originate in the outflow increases with the equivalent width of Fe II UV 44. In addition, there are several Fe II lines that are pumped by Ly-\alpha. If the Ly-\alpha emission is formed in the proximity of the circumstellar material then emission from the pumped Fe II lines may be seen. We will discuss the Herbig Ae/Be stars where the pumped Fe II lines are detected and consider the possible geometric implications.

Program listing for Thursday