EMISSION-LINE STUDIES OF YOUNG STARS .3. CORRELATIONS WITH THE INFRARED EXCESS

We use published photometry and new emission-line data to compare the IR luminosity excesses and Ca II triplet line strengths in a sample of 85 T Tauri and Herbig Ae/Be stars. We also examine the extinction-corrected spectral energy distributions and estimate the radii and luminosities of the underlying stars. Our main results are the following; (1) The spectra of several sources suggest that much of the visible flux is reflected by dust. The blue colors caused by reflection lead to underestimated extinctions (by at least approximately 1-4 mag at V) and stellar luminosities (by factors of at least approximately 2-40). (2) The excess infrared (1.0-25-mu-m) luminosities (L(IRE)) are typically larger in the high-mass sources, but are smaller relative to their stellar bolometric luminosities (L*). (3) The large ratios L(IRE)/L* greater than or similar to 1 in many of the T Tauri stars and a few of the cooler Herbig stars require that some of the IR flux originate from stellar companions or self-luminous accretion disks. The examples of T Tau and XZ Tau demonstrate the possible large contributions from IR companion stars. (4) The B-type Herbig stars all have small L(IRE)/L* ratios that are consistent with passive reprocessing disks. Small ratios also appear in the two luminous embedded young stars we consider, GL 490 and S106 IRS 3. (5) The hottest (early B) sources have the lowest L(IRE)/L* ratios, suggesting a lower efficiency for reprocessing the starlight. The reduced efficiency could be due to the intense ionizing radiation clearing the inner disks of absorbers (i.e., dust). (6) The IR excess and Ca II triplet line luminosities are roughly correlated across the entire sample (approximately 5 decades in luminosity). (7) Among the T Tauri stars the correlation is stronger than the relationship with L* and is consistent with both the lines and IR continuum being driven by accretion disks. (8) Among the Herbig stars the Ca II-L(IRE) correlation could result from accretion in some objects and reprocessing in others. Two classical Be stars, gamma-Cas and theta-Per, are used to show that the correlation can be met even when accretion is clearly not a factor. (9) Whatever excitation is involved, the existence of a Ca II-L(IRE) relationship suggests that the line-emitting envelopes are somehow related to (or perhaps contingent upon) the presence of disks. The correlation therefore argues against the stellar-driven (e.g., chromospheric) interpretation of the lines.