Detections of Rovibrational H2 Emission from the Disks of T Tauri Stars

Jeffrey S. Bary, Vanderbilt University
David Weintraub, Vanderbilt University
Joel Kastner, Rochester Institute of Technology

© 2003 The American Astronomical Society

Jan 2003 Special thanks to Tracy L. Huard for his assistance with data reduction techniques and discussions of color-color diagrams. Also, thanks to Phil Maloney, David Hollenbach, Didier Saumon, and Nuria Calvet for insightful discussions. Additional thanks to N. Calvet and Andrew Walsh for providing us with the L band photometry and G. Herczeg for providing us with FUSE continuum and line fluxes for TW Hya prior to publication. We also would like to thank KPNO staff members Hillary Mathis, Doug Williams, and Ken Hinkle for making our observing runs both productive and enjoyable. Thanks to Ginny Nickles for her assistance in making some of the observations reported herein. This work is supported by NASA grant NAG5-8295 to Vanderbilt University.ISSN:1538-4365

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We report the detection of quiescent H2 emission in the v=1→0 S(1) line at 2.12183 µm in the circumstellar environment of two classical T Tauri stars, GG Tau A and LkCa 15, in high-resolution (R~=60,000) spectra, bringing to four, including TW Hya and the weak-lined T Tauri star DoAr 21, the number of T Tauri stars showing such emission. The equivalent widths of the H2 emission line lie in the range 0.02-0.10 °A and, in each case, the central velocity of the emission line is centered at the star’s systemic velocity. The line widths range from 9 to 14 km s^−1, in agreement with those expected from gas in Keplerian orbits in circumstellar disks surrounding K-type stars at distances ≥ 10 AU from the sources. UV fluorescence and X-ray heating are likely candidate mechanisms responsible for producing the observed emission. We present mass estimates from the measured line fluxes and show that the estimated masses are consistent with those expected from the possible mechanisms responsible for stimulating the observed emission. The high temperatures and low densities required for significant emission in the v=1→0 S(1) line suggests that we have detected reservoirs of hot H2 gas located in the low density, upper atmospheres of circumstellar disks of these stars (Refer to PDF file for exact formulas).