Josh Peek edited subsubsection_Methods_204_076_29__.tex  almost 8 years ago

Commit id: d7e9feb5e9f489bcbb5befd0a26305f413e655eb

deletions | additions      

       

and the parameters of these lines clearly differentiate between the populations. Unfortunately, we do not have observations of the H$\gamma$ or H$\delta$ line, only the H$\epsilon$ line. To determine whether we can use the H$\epsilon$ line as a similar discriminator, we first assemble a sub-population of BHB, BS, and MS drawn from the catalog presented in \cite{Xue_2008}, selected to be brighter than 16th magnitude in g. These targets have already been fit, and classified, but to test our method we refit the H$\gamma$ line in the SDSS DR10 spectra using Equation \ref{sersic}, and find we can indeed reproduce the bifurcation. We then apply this same fitting procedure to the H$\epsilon$ line. The results for both fits are shown in Figure \ref{hgammahepsilon}. The H$\epsilon$ line fit sersi\'c parameters b and c do not as clearly delineate between BHB and BS stars, but the differentiation is still quite clearly in place. We then apply this same fit to our VLT/FLAMES spectrum of 204.076-29.732, and overplot the b and c parameters. 204.076-29.732 is very clearly a BHB star.  BHB stars have the useful property of being rather accurate standard candles. Using the color $g-r = -0.21$, we can measure the absolute magnitude of the star to be $M_g = 0.64$, using the values from \cite{Xue_2008} (these values are originally reported in \cite{Sirko_2004} with a typographical error). This gives 204.076-29.732 a distance of 5200 pc, 5.200 kpc,  with errors for BHB stars typically quoted at 10\%.