A Grid of NLTE Line-Blanketed Model Atmospheres of Early B-type Stars

Thierry Lanz$^1$, Ivan Hubeny$^2$

$^1$ University of Maryland
$^2$ University of Arizona

We have constructed a comprehensive grid of 1540 metal
line-blanketed, NLTE, plane-parallel, hydrostatic model
atmospheres for the basic parameters appropriate to early B-type stars. The BSTAR2006 grid considers 16 values of effective temperatures,
$15,000$,K $leq$ Teff $leq,30,000$,K with 1,000,K steps,
13 surface gravities, $1.75leqlog gleq 4.75$ with
0.25,dex steps, 6 chemical compositions, and a microturbulent velocity
of 2,km/s. The lower limit of $log g$ for a given effective temperature
is set by an approximate location of the Eddington limit.
The selected chemical compositions range from twice to one tenth
of the solar metallicity and metal-free. Additional
model atmospheres for B supergiants ($log gleq 3.0$) have been
calculated with a higher microturbulent velocity (10,km/s) and
a surface composition that is enriched in helium and nitrogen, and depleted in carbon.
This new grid complements our earlier OSTAR2002
grid of O-type stars
(Lanz~& Hubeny, 2003, ApJS, 146, 417). The paper contains a description
of the BSTAR2006 grid and some illustrative examples and comparisons.
NLTE ionization fractions, bolometric corrections, radiative accelerations,
and effective gravities are obtained over the parameter range covered by the grid.
By extrapolating radiative accelerations, we have determined an improved
estimate of the Eddington limit in absence of rotation between 55,000 and
15,000,K. The complete BSTAR2006 grid is available at the TLUSTY website.

Reference: 2007, ApJS, 169, in press
Status: Manuscript has been accepted

Weblink: http://nova.astro.umd.edu


Email: lanz@astro.umd.edu