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arXiv · 1110.2095

A 30 AU radius CO gas hole in the disk around the Herbig Ae star Oph IRS 48

Joanna M. Brown·Gregory J. Herczeg·Klaus M. Pontoppidan·Ewine F. van Dishoeck
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Abstract

The physical processes leading to the disappearance of disks around young stars are not well understood. A subclass of transitional disks, the so-called cold disks with large inner dust holes, provide a crucial laboratory for studying disk dissipation processes. IRS 48 has a 30 AU radius hole previously measured from dust continuum imaging at 18.7 micron. Using new optical spectra, we determine that IRS 48 is a pre-main sequence A0 star. In order to characterize this disk's gas distribution, we obtained AO-assisted VLT CRIRES high resolution (R ~100,000) spectra of the CO fundamental rovibrational band at 4.7 micron. All CO emission, including that from isotopologues and vibrationally excited molecules, is off-source and peaks at 30 AU. The gas is thermally excited to a rotational temperature of 260 K and is also strongly UV pumped, showing a vibrational excitation temperature of ~5000 K. We model the kinematics and excitation of the gas and posit that the CO emission arises from the dust hole wall. Prior imaging of UV-excited PAH molecules, usually a gas tracer, within the hole makes the large CO hole even more unexpected.

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Joanna M. Brown, Gregory J. Herczeg, Klaus M. Pontoppidan, Ewine F. van Dishoeck. 2011-10-10. A 30 AU radius CO gas hole in the disk around the Herbig Ae star Oph IRS 48. https://doi.org/10.1088/0004-637x%2F744%2F2%2F116

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