Horizontal Branch Stars in M3 and M13

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Session 104 -- Globilar Clusters
Display presentation, Thursday, 12, 1995, 9:20am - 6:30pm

[104.08] Horizontal Branch Stars in M3 and M13

R. O. Gray (Appalachian State U), C. J. Corbally (Vatican Observatory), J. M. Hill (Steward Observatory)

We found unexpected spectral characteristics in a set of field horizontal branch stars with spectral types near A0. They showed Balmer line wings that were broad and characteristic of high gravity stars, and further, one third of the FHB stars appeared to have normal metal line strengths despite low $m_1$ photometric indices.

To find out whether the horizontal branch stars in actual clusters show the same characteristics, we have obtained spectra of stars in M3 and in M13. Initial results of classifying these stars support our earlier findings for the FHB stars. We present some atmospheric modelling as our first attempt to understand the parameters of this kind of near-A0, horizontal branch star.

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