The $\beta$ Pictoris Phenomenon in A-Shell Stars

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Session 48 -- Young Stars
Display presentation, Tuesday, 10, 1995, 9:20am - 6:30pm

[48.07] The $\beta$ Pictoris Phenomenon in A-Shell Stars

C.A. Grady, M.R. P\'erez (ARC), A. Talavera (ESA- IUE Observatory)

We present the results of an on-going survey of IUE recent and archival spectra of A-shell stars for accreting, circumstellar gas similar to that seen toward $\beta$ Pic. Compared to previous, optical surveys, the UV, and particularly the mid-UV is rich in high-oscillator strength transitions of cosmically abundant elements, providing more sensitive probes of circumstellar material than can be obtained in optical surveys. Accreting material is detected in HD 88195, HD 38090, HD 15253, HD 38090, and HD 42111 in addition to the previously reported detections for HR 10, 51 Oph, and $\beta$ Pic. Given the limited number of IUE observations, together with the high detection rate, the available data imply that accreting circumstellar gas is routinely in the line of sight to these stars, in contrast to the classical Be stars for which accretion events are comparatively rare. The optically brighter stars in our sample are IRAS sources; given the faint V magnitudes we have detected either the presence of companions or circumstellar dust. Several of the program stars have residual H$\alpha$ emission in published spectra. Previous studies have suggested that A-shell stars represent an extension to lower stellar luminosities of the classical Be phenomenon, in which case we would expect only sporadic detections of accreting material. Nevertheless, the overall level of the accreting gas, the presence of incipient H$\alpha$ emission, and the presence of modest IR excesses, compared to Herbig Ae stars, suggests a closer link to the Herbig Ae stars and objects like $\beta$ Pic.

This study was supported under NASA Contract NASW-4756 to the Applied Research Corporation.

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