STELLAR CONTRIBUTION FUNCTIONS IN THE AGE OF CHEMICAL STRATIFICATION
Abstract
Contribution functions (CF's) were important tools to probe formation depths of features in the early numerical calculations of analytical stellar spectroscopy. In more recent work, CF's have played a minor role. Gray's (2005) text briefly discusses CF's, but CF's are not in Hubeny and Mihalas (2015). Gurtovenko and Sheminova (2015) give an extensive review of contribution functions in a recent preprint (arXiv:1505.00975). The realization that the atmospheres of certain stars are chemically stratified (Ryabchikova, Wade \& LeBlanc, 2003, in IAU Symp. 210), and much subsequent work makes CF's of current interest. We employ new as well as older methods to compute CF's to find important layers, either for specific intensity or line depth for various points on the line profile. The most important layer is the one that causes the biggest change in the magnitude of the feature when the line absorption coefficient is set equal to zero for successive layers. This is readily done for a stratified or unstratified model. For an equivalent width, W, we calculate $(W-W_i/W) $, where $W_i$ is the equivalent width without absorption from the $i^th$ layer. We concentrate on cases where stratification is most obvious, for example, the Ca II K-line profile in the roAp stars and HR 6000 (Castelli, et al. 2017, A\&A, 601, A119).
- Publication:
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American Astronomical Society Meeting Abstracts #231
- Pub Date:
- January 2018
- Bibcode:
- 2018AAS...23115705C