CAOSP abstracts, Volume: 27, No.: 3, year: 1998
- Author(s): LADSTREET, J.
- Journal: Contributions of the Astronomical Observatory Skalnate Pleso,
vol. 27, no. 3, p. 350-352.
- Date: 04/1998
- Title: Spectrum synthesis of sharp-lined A and B stars
- Keyword(s): STARS: SHARP-LINED, SPECTRUM SYNTHESIS
- Pages: 350 -- 352
I have carried out spectrum synthesis of R = 120,000 spectra of
several A and B stars having v sin i less than about 6 km/s. The following
conclusions emerge: (1) As T(e) descends from 12,000 to 8,000 K,
microturbulent velocity deduced from abundance analysis rises steadily
from 0 to about 5 km/s. (2) Stars with microturbulent velocity greater or
equal to 1 km/s show direct evidence in their line profiles of the presence
of macroscopic gas motions in the form of line asymmetry (bisector curvature)
which grows with increasing microturbulent velocity.(3) Above T(e) approx.
9,000 K, both weak and strong spectral lines can be modelled with reasonable
accuracy by conventional LTE spectrum synthesis with a single assumed
model atmosphere, abundance table, v sin i, and an appropriate (constant)
value of microturbulent velocity. (4) In contrast, at T(e) approx. 8,000 K
the weak spectral lines are much narrower than the strong lines. If the
synthesis model is constrained in v sin i and microturbulent velocity
by the weak lines, no satisfactory model can be found for the strong
spectral lines. Consequently, chemical abundances for such stars based only
on strong lines may be significantly in error.
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