Disequilibrium Chemistry on Gliese 229B

Details Disequilibrium Chemistry on Gliese 229B Disequilibrium Chemistry on Gliese 229B

Oct 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007dps....39.2203t&link_type=abstract

American Astronomical Society, DPS meeting #39, #22.03; Bulletin of the American Astronomical Society, Vol. 39, p.450

Other

2

Scientific paper

We have developed a photochemical model for the brown dwarf Gliese 229B in an attempt to explain observed CO and NH3 abundances that are clearly out of thermochemical equilibrium at 2-3 bars (cf. Noll et al. 1997, Yelle and Griffith 1999, Saumon et al. 2000, Fegley and Lodders 1996, Lodders and Fegley 2004) and to make predictions regarding the abundances of photochemically produced species. The model includes carbon, hydrogen, oxygen, and nitrogen species, and the radiative-transfer calculations include multiple Rayleigh scattering. Molecular and eddy diffusion control the vertical transport. The temperature-pressure profile and initial abundances (assumed in equilibrium) are taken from "Model B" of Saumon et al. (2000). Overall, we find that photochemical production rates are relatively low due to the large separation (44 AU) of Gliese 229B from its parent star, Gliese 229A, and to the low near-UV fluxes of M-dwarf stars like Gliese 229A. Photochemical production of constituents like CO2, HCN, and C2H6 does occur well in excess of equilibrium predictions at pressures less than 1 bar; we will discuss whether the predicted column abundances for these species are higher or lower than observational thresholds. We confirm the conclusion of Saumon et al. (2000) and Yelle and Griffith (1999) that the low observed mixing ratio of NH3 and the high observed mixing ratio of CO at 2-3 bars result from slow kinetic processes being unable to compete with more rapid vertical mixing as atmospheric temperatures decrease with altitude. We will discuss the implications of our work with regard to photochemistry on other brown dwarfs, including some of those observed by Spitzer.
This work was supported by the NASA Planetary Atmospheres Program and the LPI Summer Intern Program.

Affiliated with

Also associated with

No associations

Rating

Disequilibrium Chemistry on Gliese 229B does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Disequilibrium Chemistry on Gliese 229B, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Disequilibrium Chemistry on Gliese 229B will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1065359