Meredith L. Rawls edited More Discussion.tex  almost 9 years ago

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Figures \ref{fig:emission1} and \ref{fig:emission2} investigate whether magnetic activity has any appreciable effect on absorption lines in either star. Following the approach of \citet{fro12}, we plot each target spectrum (colored line) on top of a model (dotted line), and show the difference below (solid black line). The model spectrum is a PHOENIX BT-Settl stellar atmosphere like the one described in Section \ref{bf} \citep{all03,asp09}, with $T_{\rm{eff}} = 5000$ and $\log g = 3.0$. It has been convolved to a lower resolution much closer to that of the ARCES and TRES spectrographs.  We examine a selection of the strongest {\rm Fe}\kern 0.1em{\sc i} lines which fall in the disentangled wavelength region and are either prone to Zeeman splitting in the presence of strong magnetic fields \citep{har73}, or not \citep{sis70}. The non-magnetic lines serve as a control. We find none of the six panels of {\rm Fe}\kern 0.1em{\sc i} absorption lines in either star show any significant deviation from the model spectrum. Thus, there is no apparent Zeeman broadening, which is unsurprising for evolved red giants. Magnetic fields must be quite strong to produce this effect. However, the H$\alpha$ and {\rm Ca}\kern 0.1em{\sc ii} absorption lines lines, which can be indicators of net chromospheric emission,  are somewhat  more interesting. The H$\alpha$ line appears  significantly deeper and broader than the model in both stars. This increased equivalent width is slightly more pronounced in Star 1 than Star 2. It is unclear whether the {\rm Ca}\kern 0.1em{\sc ii} doublet shows signs of excess broadening, but neither H$\alpha$ nor {\rm Ca}\kern 0.1em{\sc ii} have \emph{smaller} equivalent widths than the model, so we do not find supporting evidence for chromospheric magnetic activity \citep{fro12}.