A Spectroscopic Survey of Subarcsecond Binaries in the Taurus-Auriga Dark Cloud
with the Hubble Space Telescope
Hartigan, P. (Rice), and Kenyon, S.J. (CfA)
We report the results of a spectroscopic survey of 20 close T Tauri binaries
in the Taurus-Auriga dark cloud where the separations between primaries and their
secondaries are less than the typical size of a circumstellar disk around a young star.
Analysis of low-resolution and medium-resolution STIS spectra yields
the stellar luminosities, reddenings, ages, masses, mass accretion rates, IR excesses, and
emission line luminosities for each star in each pair.
We examine the ability of IR color excesses, H-alpha equivalent widths,
[O I] emission, and veiling to distinguish between weak emission and classical
T Tauri stars. Four pairs have one cTTs and
one wTTs; the cTTs is the primary in three of these systems.
This frequency of mixed pairs among the close T Tauri binaries is similar to the
frequency of mixed pairs in wider young binaries.
Extinctions within pairs are usually similar; however,
the secondary is more heavily reddened than the primary in some systems,
where it may be viewed through the primary's disk.
Mass accretion rates of primaries and secondaries are strongly correlated, and
H-alpha luminosities, IR excesses, and ages also correlate within pairs.
Primaries tend to have somewhat larger accretion rates than
their secondaries do, and are typically slightly older than their secondaries according
to three different sets of modern pre-main-sequence evolutionary
tracks. Age differences for XZ Tau and FS Tau, systems embedded in
reflection nebulae, are striking; the secondary in each pair is less massive
but more luminous than the primary. The stellar masses of the UY Aur and
GG Tau binaries measured from their rotating molecular disks are about
30% larger than the masses inferred from the spectra and evolutionary
tracks. This discrepancy can be resolved in several ways, among them
a 10% closer distance for the Taurus-Auriga dark cloud.
2003, ApJ 583, 334