We present high resolution near-infrared spectra of β Pictoris - a nearby young star with a debris disk. Fundamental low-J CO absorption lines are detected and strict upper limits are placed on the flux of v=2-1 low-J CO emission lines. The limit on the UV fluorescent emission flux in the v=2-1 lines is used to place a tight constraint on the inner extent of the CO gas. Assuming \ion{H}{1} is the primary collision partner, the subthermal population of the low-J v=0 rotational levels constrains the density of the gas in the disk to nH=(2.5−1.2+7.1)×105 cm−3. If the distribution of hydrogen follows that of the other metals in the disk, we find that the mass of the gas in the disk is (0.17−0.08+0.47) M\earth. We compare this mass to the gas mass necessary to brake the metals in the disk through ion-neutral reactions.
@article{arxiv.1106.2532,
title = {Ro-vibrational CO Detected in the $\beta$~Pictoris Circumstellar Disk},
author = {Matthew R. Troutman and Kenneth H. Hinkle and Joan R. Najita and Terrence W. Rettig and Sean D. Brittain},
journal= {arXiv preprint arXiv:1106.2532},
year = {2015}
}