Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars

Astronomy and Astrophysics – Astrophysics

Scientific paper

Rate now

  [ 0.00 ] – not rated yet Voters 0   Comments 0

Details

13 pages, 7 tables, 5 figures, accepted by A&A

Scientific paper

10.1051/0004-6361:20030907

Non-LTE line formation calculations of Fe I are performed for a small number of reference stars to investigate and quantify the efficiency of neutral hydrogen collisions. Using the atomic model that was described in previous publications, the final discrimination with respect to hydrogen collisions is based on the condition that the surface gravities as determined by the Fe I/Fe II ionization equilibria are in agreement with their astrometric counterparts obtained from HIPPARCOS parallaxes. Depending on the choice of the hydrogen collision scaling factor S_H, we find deviations from LTE in Fe I ranging from 0.00 (S_H = infinity) to 0.46 dex (S_H = 0 for HD140283) in the logarithmic abundances while Fe II follows LTE. With the exception of Procyon, for which a mild temperature correction is needed to fulfil the ionization balance, excellent consistency is obtained for the metal-poor reference stars if Balmer profile temperatures are combined with S_H = 3. The correct choice of collisional damping parameters ("van-der-Waals" constants) is found to be generally more important for these little evolved metal-poor stars than considering departures from LTE. For the Sun the calibrated value for S_H leads to average Fe I non-LTE corrections of 0.02 dex and a mean abundance from Fe I lines of log epsilon(Fe) = 7.49 \pm 0.08. We confront the deduced stellar parameters with comparable spectroscopic analyses by other authors which also rely on the iron ionization equilibrium as a gravity indicator. On the basis of the HIPPARCOS astrometry our results are shown to be an order of magnitude more precise than published data sets, both in terms of offset and star-to-star scatter.

No associations

LandOfFree

Say what you really think

Search LandOfFree.com for scientists and scientific papers. Rate them and share your experience with other people.

Rating

Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars 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 Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Kinetic equilibrium of iron in the atmospheres of cool stars III. The ionization equilibrium of selected reference stars will most certainly appreciate the feedback.

Rate now

     

Profile ID: LFWR-SCP-O-265800

  Search
All data on this website is collected from public sources. Our data reflects the most accurate information available at the time of publication.