BOLOMETRIC TEMPERATURE AND YOUNG STARS IN THE TAURUS AND OPHIUCHUS COMPLEXES

We calculated bolometric temperature (T-bol) and luminosity (L(bol)) f or 128 young stellar objects (YSOs) in Taurus, 74 in the Ophiuchus ''c ore,'' and 33 in the Ophiuchus ''off-core'' region. We have constructe d the bolometric luminosity-temperature (BLT) diagram, the log-log plo t of L(bol) versus T-bol, for the three samples. T-bol is defined as t he temperature of a blackbody having the same frequency as the observe d continuum spectrum. It measures the redness (or coldness) of an astr onomical source. The BLT diagram is analogous to the H-R diagram and a llows for a direct and quantitative comparison of YSOs at a wide varie ty of evolutionary states, ranging from the most deeply embedded stars to T Tauri stars nearly on the main sequence. We found (1) T-bol incr eases monotonically from embedded sources (similar to 60-500 K) to cla ssical T Tauri stars (similar to 1000-3000 K) to weak-line T Tauri sta rs (similar to 2000-5000 K); (2) T-bol correlates reasonably well with the age inferred from the evolutionary models of pre-main-sequence st ars and protostars for embedded ''protostars'' and weak-line T Tauri s tars. There is no significant correlation for the classical T Tauri st ars. These results can be understood in terms of dissipation of circum stellar dust envelope and disk during the early stages of stellar evol ution. Sources in the three regions have different distributions in th e BLT diagram. The Ophiuchus core has the highest fraction of cold sou rces among the three regions. These cold sources are also more luminou s than the YSOs in the other regions. The Ophiuchus off-core sample is dominated by the more evolved pre-main-sequence stars. The Taurus sou rces have distributions intermediate in L(bol), T-bol, and age between the Ophiuchus core and off-core distributions. These may suggest diff erences in the star formation history, and possibly in the stellar mas ses and mass accretion rates in these star-forming regions.