Title: The Exceptionally Bright Carbon-Enhanced Metal-Poor Star BD+44 493
Author(s): H. Ito, W. Aoki, S. Honda, and T. C. Beers

Abstract:
We present a 1D LTE chemical abundance analysis of the very bright (V=9.1) 
carbon-enhanced metal-poor (CEMP) star BD+44 493, based on high-resolution, 
high signal-to-noise spectra obtained with Subaru/HDS. The star is shown to 
be subgiant with an extremely low iron abundance ([Fe/H]=-3.7), and rich 
in C ([C/Fe]=+1.3) and O ([O/Fe]=+1.6). Because its neutron-capture elements 
are not over-abundant, BD+44 493 is a new member of the ``CEMP-no" class of 
stars. Its abundance pattern implies that a first-generation faint supernova 
is the most likely origin of its carbon excess, while scenarios related to 
mass loss from rapidly rotating massive stars and binary mass transfer from 
an AGB companion star are not favored. Based on an excellent spectrum in the 
UV region, we set an very low upper limit on this star's beryllium abundance 
(A(Be)=log(Be/H)+12<-2.0), which indicates that the decreasing trend of Be 
abundances with lower [Fe/H] still holds at [Fe/H]<-3.5. This is the first 
attempt to measure a Be abundance for a CEMP star, and demonstrates that 
high C and O abundances do not necessarily imply high Be abundances.