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| Paper: |
HST/COS Spectra of DF Tau and V4046 Sgr: First Detection of Molecular Hydrogen Absorption Against the Lyman α Emission Line |
| Volume: |
448, 16th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun |
| Page: |
69 |
| Authors: |
Yang, H.; Linsky, J. L.; France, K. |
| Abstract: |
We present moderate-resolution (16,000 – 18,000) far-UV spectra of two
classical T Tauri stars, DF Tau and V4046 Sgr, obtained with
the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope
(HST), and report for the first time detection of absorption in the Lyman-α profile produced
by the H2 pumping transitions. For most absorption features, the absorbed energy in the H2
pumping transitions is significantly smaller than the amount of energy in the resulting fluorescent emission, indicative of
additional absorption in the H I Lyman-α profile along our light of sight. We model the additional H I absorption
and are able to correct the H2 absorption/emission ratios close to unity.
The required H I absorption for DF Tau is at a velocity close to the radial velocity of the star,
consistent with H I absorption in the interstellar medium and the edge-on disk. For V4046 Sgr, a nearly face-on system,
the required absorption is near +290 km s-1, most likely resulting from H I gas in the accretion
columns falling onto the star. |
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