Radiative Accelerations and Equilibrium Abundances of Metals for DA White Dwarfs below 25,000K

Details Radiative Accelerations and Equilibrium Abundances of Metals for DA White Dwarfs below 25,000K Radiative Accelerations and Equilibrium Abundances of Metals for DA White Dwarfs below 25,000K

Jan 2010

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010aas...21545205d&link_type=abstract

American Astronomical Society, AAS Meeting #215, #452.05; Bulletin of the American Astronomical Society, Vol. 42, p.461

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Scientific paper

Heavy elements detected in the atmospheres of hot white dwarfs are commonly explained in terms of a diffusion model involving an equilibrium between radiative forces and gravity. In spite of the declining relative importance of radiative accelerations at lower effective temperatures, an increasing number of cooler DA white dwarfs are also found to host significant abundances of metals in their atmosphere. In these cases, accretion of circumstellar matter appears to be the source of detected metals. To better assess the potential influence of radiative accelerations on the metallicity of cooler DA white dwarfs, we performed new radiative accelerations calculations in DA envelopes with effective temperatures between 12,500K and 25,000K for C, N, O, Ne, Na, Mg, Al, Si, S, Ar, Ca, and Fe. The results are compared with a metal abundance analysis of a sample of 19 stars observed with FUSE. The main elements predicted to be supported by radiative acceleration over this temperature range are C, Si, and Al, in line with the FUSE observations where only C and Si have been detected in most objects. For the other elements, we confirm that radiative acceleration can be safely neglected when computing steady-state abundances in the accretion-diffusion framework.

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