A tidally interacting disk in the young triple system WL 20?

Creators: Barsony, Mary; Greene, Thomas P.; Blake, Geoffrey A.

Abstract

We present high-resolution λ = 2.7 mm imaging of the close triple pre-main-sequence system WL 20. Compact dust emission with integrated flux density of 12.9 ± 1.3 mJy is associated with two components of the triple system, WL 20W and WL 20S. No emission above a 3 σ level of 3.9 mJy is detected toward the third component, WL 20E, which lies 3."17 (400 AU) due east in projection from its neighbors. A possibly warped structure of ~0.1 M_☉ and ≤3."2 extent encompasses WL 20W and WL 20S, which have a projected separation of 2."25 (~280 AU) along a north-south axis. This structure is most likely a tidally disrupted disk surrounding WL 20S. New near-infrared spectra of the individual components show a remarkable similarity between the two T Tauri stars of the system: WL 20E has a K7 spectral type (T_eff = 4040 K) with r_K = 0.2, and WL 20W has an M0 spectral type (T_eff = 3800 K) with r_K = 0.2. The spectrum of WL 20S is consistent with that of a source intrinsically similar to WL 20W, with r_K < 0.9, but seen through an A_V = 25 in addition to the A_V = 16.3 to the system as a whole. Taken together, these millimeter and infrared data help explain the peculiar nature of the infrared companion, WL 20S, as resulting from a large enhancement in its dusty, circumstellar environment in relation to its companions.

Additional Information

© 2002 American Astronomical Society. Received 2002 March 26; accepted 2002 May 2; published 2002 May 14. We would like to thank Al Wootten, the staff at OVRO, Ralf Launhardt, and Adwin Boogert for help with OVRO data acquisition and reduction and for useful scientific discussions. The authors also extend special thanks to Marianne Takamiya for taking the NIRSPEC data and to NOAO for granting Gemini/NIRSPEC observing time. We wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. The Owens Valley millimeter-wave array is supported by NSF grant AST 99-81546. M. B. acknowledges financial support from NASA's Long Term Space Astrophysics Research Program, NAG5-8412.

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