Astronomy & Astrophysics

Free access article

A&A 459, L29-L32 (2006)
DOI: 10.1051/0004-6361:20066306

Letter

X-ray accretion signatures in the close CTTS binary V4046 Sagittarii

H. M. Günther¹, C. Liefke¹, J. H. M. M. Schmitt¹, J. Robrade¹ and J.-U. Ness²

¹ Hamburger Sternwarte, Gojenbergsweg 112, 21029 Hamburg, Germany
e-mail: moritz.guenther@hs.uni-hamburg.de
² Arizona State University, School of Earth and Space Exploration, Tempe, AZ, 85287-1404, USA

(Received 28 August 2006 / Accepted 26 September 2006)

Abstract
We present Chandra HETGS observations of the classical T Tauri star (CTTS) V4046 Sgr . The He-like triplets of $\ion{O}{vii}$ , $\ion{ix}$ , and $\ion{xiii}$ are clearly detected. Similar to the CTTS TW Hya and BP Tau, the forbidden lines of $\ion{O}{vii}$ and $\ion{ix}$ are weak compared to the intercombination line, indicating high plasma densities in the X-ray emitting regions. The $\ion{xiii}$ triplet, however, is within the low-density limit, in agreement with the predictions of the accretion funnel infall model with an additional stellar corona. V4046 Sgr is the first close binary exhibiting these features. Together with previous high-resolution X-ray data on TW Hya and BP Tau , and in contrast to T Tau , now three out of four CTTS show evidence of accretion funnels.

Key words: X-rays: stars -- stars: individual: V4046 Sagittarii -- stars: pre-main sequence -- stars: coronae -- stars: activity

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