Spectroscopic study of the late B-type eclipsing binary system AR Aurigae A and B: Towards clarifying the differences in atmospheric parameters and chemical abundances

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Abstract AR Aur A+B is a close binary of astrophysical interest, because dissimilar 
surface compositions are reported between similar late B-type dwarfs. 
A new spectroscopic study on this system was carried out based on the 
disentangled spectra, in order to determine their atmospheric parameters 
and elemental abundances,
The effective temperature and microturbulence (determined from the 
equivalent widths of Fe II lines) turned out (11150K, 0.9km/s) 
and (10650K, 0.1km/s) for A and B.
The chemical abundances of 28 elements were derived while taking 
into account the non-LTE effect for Z<=15 elements (Z: atomic number). 
The following trends were elucidated for [X/H] (abundance of X relative to the Sun): 
(1) Qualitatively, [X/H] shows a rough global tendency of increasing 
with Z, with the gradient steeper for A than for B. 
(2) However, considerable dispersion is involved for A, since 
prominently large peculiarities are seen in specific elements reflecting 
the characteristics of HgMn stars (e.g., very deficient N, Al, Sc, Ni; 
markedly overabundant P, Mn).
(3) In contrast, the Z-dependence of [X/H] for B tends to be nearly 
linear with only a small dispersion. These observational facts may serve as
a key to understanding the critical condition for the emergence of chemical 
anomaly.