Improved Atomic Transition Probabilities for UV and Optical Lines of Hf II and Determination of the Hf Abundance in Two Metal-Poor Stars
| Autor: | E. A. Den Hartog, Ian U. Roederer, James E. Lawler |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Physics
Branching fraction 05 social sciences 050301 education Sigma FOS: Physical sciences Astronomy and Astrophysics Atomic spectroscopy 01 natural sciences Astrophysics - Astrophysics of Galaxies Metal Wavelength Stars Astrophysics - Solar and Stellar Astrophysics Space and Planetary Science visual_art Astrophysics of Galaxies (astro-ph.GA) 0103 physical sciences Radiative transfer visual_art.visual_art_medium Wavenumber Atomic physics 010303 astronomy & astrophysics 0503 education Solar and Stellar Astrophysics (astro-ph.SR) |
| Popis: | We report new branching fraction measurements for 199 UV and optical transitions of Hf II. These transitions range in wavelength (wavenumber) from 2068- 6584 A (48322-15183 cm-1) and originate in 17 odd-parity upper levels ranging in energy from 38578-53227 cm-1. The branching fractions are combined with radiative lifetimes reported in an earlier study to produce a set of transition probabilities and log(gf) values with accuracy ranging from 5-25%. Comparison is made to transition probabilities from the literature where such data exist. We use these new transition probabilities to derive improved Hf abundances in two metal-poor stars. HD 196944 is enhanced in s-process elements, and we derive log epsilon (Hf) = -0.72 +/- 0.03 (sigma = 0.09) from 12 Hf II lines. HD 222925 is enhanced in r-process elements, and we derive log epsilon (Hf) = 0.32 +/- 0.03 (sigma = 0.11) from 20 Hf II lines. These measurements greatly expand the number of potentially useful Hf II lines for analysis in UV and optical spectra. Accepted for publication in the Astrophysical Journal Supplement Series (32 pages, 4 figures, 4 tables) |
| Databáze: | OpenAIRE |
| Externí odkaz: |
|