Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009mnras.396.2201i&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 396, Issue 4, pp. 2201-2210.
Astronomy and Astrophysics
Astronomy
1
Atomic Processes, Molecular Processes, Radiation Mechanisms: General, Radiative Transfer, Stars: Atmospheres
Scientific paper
The main aim of this work is to estimate the total contribution of the processes of molecular ion photodissociation and collisional absorption charge exchange to the opacity of DB white dwarf atmospheres, and compare this with the contribution of and other relevant radiative absorption processes included in standard models.
The method for the calculations of the molecular ion photodissociation cross-sections is based on the dipole approximation and quantum-mechanical treatment of the internuclear motion, while the quasi-classical method for describing absorption processes in collisions is based on the quasi-static approximation.
Absorption coefficients are calculated in the region 50nm<= λ <= 850nm and compared with the corresponding coefficients of other relevant absorption processes; the calculations of the optical depth of the atmosphere layers considered are performed in the far-UV and VUV regions; the contribution of the relevant absorption processes to the opacity of DB white dwarf atmospheres is examined.
We examined the spectral ranges in which the total and absorption processes dominate in particular layers of DB white dwarf atmospheres. In addition, we show that in the region of λ <~ 70nm the process of atom photoionization is also important, in spite of the fact that the ratio of hydrogen and helium abundances in the DB white dwarf atmosphere considered is 1:105.
Dimitrijevic Milan S.
Ignjatović Lj M.
Metropoulos A.
Mihajlov Anatolij A.
Sakan Nenad M.
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