2004ApJ...601L..87D

We report infrared spectroscopy of the unusual eclipsing pre-main-sequence object KH 15D, obtained using NIRSPEC on Keck II. During eclipse, observations using low spectral resolution (λ/δλ∼1000) reveal the presence of prominent molecular hydrogen emission in five lines near 2 µm. The relative line strengths are consistent with thermal excitation at T∼2800±300 K. Observations out of eclipse, at both low and high spectral resolution (λ/δλ∼2x10⁴), show reduced contrast with the stellar continuum. The change in contrast for the strongest line, 1-0 S(1), is consistent with an approximately constant emission line superposed on a variable stellar continuum. Emission in the 1-0 S(1) line is observed to extend by ≳4" both east and west of the stellar point-spread function (PSF; ≳3000 AU). Observed at high spectral resolution, the velocity and the intensity structure of the 1-0 S(1) profile are both asymmetric. East of the stellar PSF (by 1".1-2".3) the emission is blueshifted (-63 km/s) and has significantly greater intensity than the marginally redshifted component (+2 km/s, approximately consistent with zero) that dominates west of the stellar PSF. The spatial extent of the emission and the excitation temperature suggest shock excitation of ambient gas by a bipolar outflow from the star and/or the disk. However, it is difficult to account for the observed radial velocity unless the outflow axis is inclined significantly to the plane of the sky.