Accretion in Taurus PMS binaries: a spectroscopic study

TL;DR

This spectroscopic study of 14 T Tauri binary systems in Taurus reveals that most binaries are twin-like in accretion activity, with the more massive star generally accreting more, supporting synchronized accretion over separations up to 13 arcseconds.

Contribution

The paper provides new spectroscopic data on Taurus T Tauri binaries, demonstrating that binary stars tend to have similar ages and accretion histories, with the more massive star usually accreting more.

Findings

Mixed binaries (CTTS+WTTS) are rare (15-20%).

Binary T Tauri stars tend to be twins in accretion activity.

The more massive star usually has a higher accretion rate, up to ten times that of its companion.

Abstract

We present low-resolution optical spectra of each component of 10 T Tauri (TT) binary systems with separations ranging from 0.9" to 3.5" and located in the Taurus star-forming region. We derive the spectral type and Halpha equivalent width of each component. Complementing these results with those of Monin et al. (1999) yields a sample of 14 binaries and one triple system, with resolved spectroscopy and/or near-infrared photometry. We find that mixed binaries (CTTS+WTTS) are rare, representing only 15-20% of the systems in the separation range of 0.8" to 3''. Supplementing these results with those of Hartigan et al. (1994) and Prato & Simon (1997), we show that the trend of binary TTS to be twins holds to separations up to 13''. This is unlikely to be the result of random pairing, and confirms previous results that both stars in young binaries accrete over the same time span. In binary systems where both stars are still accreting, our measurements show that the most massive star is usually the component with the largest accretion rate by up to a factor of 10, as determined from the Halpha luminosity.