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Published September 20, 2012 | Published
Journal Article Open

Locating the Trailing Edge of the Circumbinary Ring in the KH 15D System

Abstract

Following two years of complete occultation of both stars in the binary T Tauri star KH 15D by its opaque circumbinary ring, KH 15D has abruptly brightened again during apastron phases, reaching I = 15 mag. Here, we show that the brightening is accompanied by a change in spectral class from K6/K7 (the spectral class of star A) to ~K1, and a bluing of the system in V – I by about 0.3 mag. A radial velocity measurement confirms that, at apastron, we are now seeing direct light from star B, which is more luminous and of earlier spectral class than star A. Evidently, the trailing edge of the occulting screen has just become tangent to one anse of star B's projected orbit. This confirms a prediction of the precession models, supports the view that the tilted ring is self-gravitating, and ushers in a new era of the system's evolution that should be accompanied by the same kind of dramatic phenomena observed from 1995 to 2009. It also promotes KH 15D from a single-lined to a double-lined eclipsing binary, greatly enhancing its value for testing pre-main-sequence models. The results of our study strengthen the case for truncation of the outer ring at around 4 AU by a sub-stellar object such as an extremely young giant planet. The system is currently at an optimal configuration for detecting the putative planet and we urge expedient follow-up observations.

Additional Information

© 2012 American Astronomical Society. Received 2012 July 23; accepted 2012 August 24; published 2012 September 7. We thank Geoff Marcy for helping to arrange the Keck/HIRES observations. We are grateful to the observers and personnel at the SMARTS and GNIRS facilities. This work was partially supported by a NASA grant to W.H. through the Origins of Solar Systems program. Based on observations obtained at theGemini Observatory via queue program GN-2010B-Q-52. Gemini is operated by the Association of Universities for Research in Astronomy, Inc., under an agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (U.S.), the Science and Technology Facilities Council (U.K.), the National Research Council (Canada), CONICYT (Chile), the Australian Research Council (Australia), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Ministerio de Ciencia, and Tecnología e Innovación Productiva (Argentina).

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