Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities

Details Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities

Jun 2001

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2001a%26a...372..260c&link_type=abstract

Astronomy and Astrophysics, v.372, p.260-275 (2001)

Astronomy and Astrophysics

Astrophysics

16

Stars: Atmospheres, Stars: Fundamental Parameters, Stars: Individuals: Hd 125162 (Lambda Boo), Ultraviolet: Stars

Scientific paper

New opacity distribution functions (ODF) have been computed for use with the ATLAS9 model atmosphere code of Kurucz. One of the improvements upon the Kurucz (\cite{kur90}) ODFs is the addition to the line blanketing of the Lyman-alpha H-H and H-H+ quasi-molecular absorptions near 1600 Å and 1400 Å. New-ODF fluxes are expected to reproduce the ultraviolet observations of lambda Boo stars and metal-poor A-type stars in a more realistic way than previous computations did. In this paper we compare low- and high-resolution IUE observations of lambda Boo (HD 125162, HR 5351) with fluxes and synthetic spectra based on ATLAS9 models and new-ODFs, which were computed for [M/H]=-2.0 for all the elements, except CNO. For C, N, and O, abundances log (Nelem/Ntot) equal to -3.85, -3.99, and -3.11, respectively, were adopted. We selected lambda Boo in order to compare results from the new-ODFs with those from Allard et al. (\cite{allar98a}, \cite{allar98b}), who tested their semi-classical computations of the H-H and H-H+ quasi-molecular absorptions on this star. The analysis of the IUE high-resolution spectrum has shown that lines of H2 are a very important source of line opacity for lambda Boo shortward 1600 Å. When both atomic and molecular lines are considered, the slope of the observed energy distribution is well reproduced in the whole region 1300-3000 Å by the new-ODF model, but the H-H quasi-molecular absorption at 1600 Å is computed about 10% too strong. The fit of the low-resolution IUE image SWP17872 to a small grid of new-ODF models gives parameters Teff= 8650 K, log g=4.0, while the fit of the high-resolution image SWP42081, rebinned at the low resolution wavelength step size, gives parameters Teff=8500 K, log g=4.0. These last parameters are in close agreement with Teff=8550 K, log g=4.1 obtained by fitting the visible energy distribution. The different IUE images are discussed.

Affiliated with

Also associated with

No associations

Rating

Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.

If you have personal experience with Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Ultraviolet spectra for lambda Boo (HD 125162) computed with H2 opacities and Lyman-alpha H-H and H-H+ opacities will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFWR-SCP-O-1580022