Article

A NLTE study of neutral boron in solar-type stars

Astronomy and Astrophysics (Impact Factor: 5.08). 05/1994; 286:169-180.
Source: arXiv

ABSTRACT The formation of the resonance lines of neutral boron in solar-type
stellar atmospheres is investigated taking into account effects of
departures from local thermodynamic equilibrium (NLTE effects). The
latter are due to a combination of overionisation and optical pumping in
resonance lines, both caused by the hot, non-local, ultraviolet
radiation fields in the line-forming regions. They lead to an
underestimation of the boron abundance when analysis methods assuming
local thermodynamic equilibrium (LTE) are used. The abundance
correction, for the 249.7 nm resonance line, amounts to +0.56 dex for
the metal-poor star HD 140283 and +0.4 dex for Procyon. No significant
NLTE effects are predicted for the Sun. Applying the abundance
correction on the results for HD 140283 of Duncan et al. (1992) leads to
a B/Be ratio well above the minimum value required by spallation
production of beryllium. The reliability of the results in view of
atomic and atmospheric uncertainties is discussed. With the possible
exception of photospheric inhomogeneity, it seems unlikely that these
could remove the effect for HD 140283.

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