A magnitude-limited spectroscopic and photometric survey of rho OphiuchusX-ray sources.

A total of 47 optical-counterpart candidates of X-ray sources in the Rho Ophiuchus (RO) dark cloud are investigated with low- and medium-resolution spectrograms and visual and near-IR photometry. The spectra of 27 stars demonstrate H-alpha emission above the continuum with an equivalent width of 10 A. The emission-line stars are characterized by Li-I 6707 absorption which along with the H-alpha data suggests that these are pre-main-sequence cloud members. Optical counterparts of the 24 X-ray sources are identified and total 30 pre-main-sequence stars, and the average age and mass range are found to be 10 exp 6 to 10 exp 7 yr and 0.3-2.5 solar mass, respectively. The RO dark cloud X-ray sources are considered to have optical counterparts that are T Tauri stars with weak emission lines. The optical counterparts are theorized to be similar to T Tauri objects in other stellar-formation regions in terms of evolutionary status.