Spectroscopic Survey of H<i>α</i> Emission Line Stars Associated with Bright Rimmed Clouds

Abstract

The results of a spectroscopic survey of H α emission line stars associated with fourteen bright rimmed clouds are presented. Slit-less optical spectroscopy was carried out with the Inter University Centre for Astronomy and Astrophysics (IUCAA) 2 m telescope and IUCAA Faint Object Spectrograph and Camera (IFOSC). H α emission line was detected from 173 objects. Among them 85 objects have a strong H α emission line with its equivalent width larger than 10 ? . Those are classical T Tauri stars. 52 objects have a weak H α emission line with its equivalent width less than 10 ? and do not show intrinsic near-infrared excess. Those are weak-line T Tauri stars. On the other hand, 36 objects have a weak H α emission line (<10 ? ), although they show intrinsic near-infrared excess. Such objects are not common in low-mass star forming regions. Those are misfits of the general concept on formation process of a low-mass star, in which it evolves from a classical T Tauri star to a weak-line T Tauri star. Those might be weak-line T Tauri stars with a flared disk in which gas is heated by ultraviolet radiation from a nearby early-type star. Alternatively, we propose pre-transitional disk objects as their evolutional stage.