2002/06/11 by Adam Burrows, R. S. Ram, Peter Bernath +2 · 1 citation
Physics and Astronomy · #astro-ph
paper · pdf · doi:10.1086/342242
published as Astrophys.J. 577 (2002) 986-992 · Includes 3 color figures (in .gif format). Accepted to the Astrophysical Journal
arxiv created 2002/06/11 · arxiv updated 2009/12/01
In this paper, we calculate new line lists and opacities for the 12 bands of the A6Σ+ -- X6Σ+ transitions of the CrH molecule. Identified in objects of the new L dwarf spectroscopic class (many of which are brown dwarfs), as well as in sunspots, the CrH molecule plays an important role in the diagnosis of low-temperature atmospheres. As a tentative first application of these opacities, we employ our new theoretical CrH data in an atmospheres code to obtain a CrH/H2 number ratio for the skin of the L5 dwarf 2MASSI J1507038-151648 of ∼ 2-4× 10-9, in rough agreement with chemical equilibrium expectations. Since in previous compilations the oscillator strength was off by more than an order of magnitude, this agreement represents a modest advance. However, in order to determine the CrH abundance in an L dwarf atmosphere, silicate clouds need to be incorporated into the model, and cloud modeling is still in a primitive stage of development. Nevertheless, one important step in L dwarf modeling is a reliable CrH opacity and this is what we have here attempted to provide.