Reproduction of the Wilson-Bappu Effect Using PHOENIX
Abstract
We use the versatile PHOENIX atmospheric modeling code in its version, which includes a gravity-scaled chromosphere above the temperature minimum to model the Ca II K emission line profile for solar-type stars, all with T_{eff} = 5780K and same turbulence broadening, only with different surface gravities. Models, which produce the modest emission observed in relatively inactive stars, reproduce the Wilson-Bappu effect (WBE) in absolute terms, i.e. the emission line-widths grow with lower gravity consistent with Δ W ∝ g^{-0.17} in the range of log{g}=5.0 to 3.5. Further modeling is in process to include lower gravities. In the solar case, which we used as a first test, we find the temperature minimum (over height, single component) for a relatively inactive Sun to reach down to 3930 K. The respective PHOENIX model (log{g} = 4.4) matches width and typical flux of the chromospheric Ca II emission of a nearly inactive Sun, as observed with the Hamburg robotic telescope (see Fig. 1). For comparison, the quiet Sun model C of tet{1981ApJS...45..635V} had a temperature minimum of 4170 K.
- Publication:
-
18th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun
- Pub Date:
- January 2015
- Bibcode:
- 2015csss...18..405O