tokens: of Zr 2 + initially in the excited level versus photon energy. For the online material, we provide the complete set of photoionization cross-sections from ground and excited levels of Sr, Y + , and Zr 2 + in a TOP format (The Opacity Project Team 1995 ), and the complete set of bound–bound photoexcitation transition coefficients for all the electric-dipole-allowed transitions within the same set of levels for these three parent ions. To ensure the files maintain a reasonable downloadable size, of the order of megabytes, we convoluted the cross-sections to reduce their size to around one thousand points in each initial level. The complete photoionization cross-sections, without any convolution, are available for any user under request. These cross-sections can be used for modelling the opacity of astrophysical objects, such as stellar atmospheres. 5 MODELLING OF STELLAR ATMOSPHERE Using sterne , we calculated models for the atmosphere of LS IV-14 116 assuming base parameters given in Table 6 for effective temperature T eff , surface gravity g , microturbulent velocity v turb , fractional abundances by number for hydrogen, helium, carbon, and nitrogen n i , and logarithmic abundances of heavier species relative to solar . For Sr, Y, and Zr, we used two values, one being scaled to the light metals Ca – Mn (the reference model), and the second enhanced by a factor of (+4.3 dex), which corresponds approximately to the overabundances observed in LS IV-14 116. Table 6. Model atmosphere parameters for LS IV-14 116. We construct 10 different models in three groups. All models include the photoionization cross-sections calculated here for Sr 0 , Y + , and Zr 2 + . The reference model has no enhancement in the abundances of these elements. There are four models that include abundances of Sr, Y, and Zr enhanced by +4.3 dex, each individually and all collectively. The third group of models includes a revised linelist with the calculated photoexcitation transitions of the parent ions Sr 0 , Y + , and Zr 2 + , and the ionization products Sr + , Y 2 + , and Zr 3 + . Again, Sr, Y, and Zr are enhanced by +4.3 dex, individually and collectively. In addition, two models were computed with the Zr 2 + and Zr 3 + lines included separately. Fig. 5 (top left-hand panel) shows the temperature structure of model atmospheres T versus optical depth τ 4000 for different abundances of Sr, Y, and Zr. Remaining panels show the temperature relative difference (per cent) to the reference model for various cases. Results imply that the new photoionization cross-section makes negligible difference to the total opacity, even with the high abundances adopted. The photoexcitation transitions make a modest temperature difference in the line-forming region (0.01 τ 4000 1), but only due to a number of very strong Zr lines. This difference corresponds to a temperature increase of up to . Figure 5. The temperature structure of model atmospheres with a -fold (+4.3 dex)
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