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New CrH opacities for the study of L and brown dwarf atmospheres

Burrows, A., Ram, R.S., Bernath, P., Sharp, C.M. and Milsom, J.A. (2002) New CrH opacities for the study of L and brown dwarf atmospheres. The Astrophysical Journal, 577 (1). pp. 986-992. ISSN 0004 637X

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In this paper, we calculate new line lists and opacities for the 12 bands of the A 6Σ+-X 6Σ+ 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 fit the CrH abundance in the L dwarf spectral class, silicate clouds need to be incorporated into the model. Given that this subject is still in a primitive stage of development, one should view any spectral model in the L dwarf range as merely tentative. Nevertheless, a necessary first step in L dwarf modeling is a reliable CrH opacity algorithm, and this is what we have here attempted to provide.

Item Type: Article
Institution: The University of York
Academic Units: The University of York > Chemistry (York)
Depositing User: York RAE Import
Date Deposited: 10 Feb 2009 16:33
Last Modified: 10 Feb 2009 16:33
Published Version: http://dx.doi.org/10.1086/342242
Status: Published
Publisher: American Astronomical Society
Identification Number: 10.1086/342242
URI: http://eprints.whiterose.ac.uk/id/eprint/7600

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