A High Spatial Resolution Infrared View of the T Tauri Multiple System

Abstract

We present the results of our monitoring study of the IR photometric and spectroscopic variability of the T Tau multiple system. We also present data on the apparent position of T Tau S with respect to T Tau N, and two new spatially resolved observations of the T Tau Sa-Sb binary. T Tau N has not varied by more than 0.2 magnitudes in K and L' flux during the 8 years of our observations, though its Br gamma and Br alpha emission line fluxes have varied by nearly a factor of four during this time. For the unresolved T Tau S system, we have derived a 20 year light curve based on our images and on measurements available in the literature. T Tau S varies by 2-3 magnitudes in K and L'-band brightness in a ``redder when faint'' manner, consistent with changes along the line of sight in the amount of material that follows an ISM extinction law. Absorption in the 3.05um water-ice feature is seen only in the spectra of T Tau S and it displays variations in depth and profile. H_2 (2.12 um) emission is also detected only at the position of T Tau S; the H_2, Br gamma and Br alpha emission line fluxes also vary. We have found that the apparent positions of T Tau S with respect to T Tau N and T Tau Sb with respect to Sa are consistent with gravitationally bound orbital motion. The possible orbits of the T Tau S binary imply that Sa is likely the most massive component in this young triple. A reanalysis of the motion of the radio source associated with T Tau S provides no evidence for an ejection event in the T Tau system.Comment: 49 pages, including 17 figures. Accepted for publication in the Astrophysical Journa

Examining the T Tauri system with SPHERE

“…Previous studies found H 2 emission around T Tau N and S (Kasper et al 2002;Beck et al 2004;Gustafsson et al 2010), which our observations also confirm. Our CntK2, Br-γ, and H 2 images (Fig.…”

“…This is in marked contrast to the latest K-band brightness ratio measurements, obtained in January 2014, in which Sa was about 0.8 mag fainter than Sb (Schaefer et al 2014). This variability of T Tau Sa of 1.7 mag in less than a year is similar to the photometric behaviour shown prior to 2006 (Beck et al 2004;Duchêne et al 2005), and demonstrates that the period of lesser variability reported from −2013(van Boekel et al 2010Schaefer et al 2014) has come to an end.…”

Accurate stellar masses in the multiple system T Tauri

“…This requires one to assume that the IR flux ratio within the T Tau S system remains constant. Evidence for large variability in at least one of the two components of the system is growing, however (Ghez et al 1991;Beck et al 2004).…”

“…All astrometric measurements listed in Beck et al (2004) and Duchêne et al (2005) are included in our fit 1 . Two additional observations of the system were recently published by Mayama et al (2006).…”

“…While it has been suggested that this system may be on an unbound orbit (Loinard et al 2003), other studies have found possible closed orbits and derived a total mass of 2−6 M for T Tau S (Johnston et al 2003;Beck et al 2004). Using a refined method, Johnston et al (2004a,b) attempted for the first time to determine the individual masses of T Tau Sa and Sb.…”