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PERIOD LUMINOSITY RELATIONS FOR RR LYRAE STARS

PERIOD LUMINOSITY RELATIONS FOR RR LYRAE STARS. Horace Smith (Michigan State University) Marcio Catelan (Pontificia Universidad Catolica de Chile) Barton Pritzl (Macalester College). RR Lyrae stars. Traditional population II distance indicators

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PERIOD LUMINOSITY RELATIONS FOR RR LYRAE STARS

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  1. PERIOD LUMINOSITY RELATIONS FOR RR LYRAE STARS Horace Smith (Michigan State University) Marcio Catelan (Pontificia Universidad Catolica de Chile) Barton Pritzl (Macalester College)

  2. RR Lyrae stars • Traditional population II distance indicators • They are on the “horizontal branch” so all RR Lyrae should have the same absolute magnitude, shouldn’t they?

  3. RR Lyrae luminosities • What do theoretical period-luminosity relations look like for RR Lyrae stars? • How do the relations depend upon the filter used? • How do the theoretical relations compare with observed period-luminosity relations?

  4. Why the difference? • Period increases with increasing luminosity or decreasing temperature • At B, the effects of the HB slope in Teff and L are nearly orthogonal • At I, the effects of the HB slope in Teff and L are in the same sense

  5. Results in more filters

  6. How do the P-L relations depend upon HB morphology? • Use the parameter L to characterize HB morphology L = (B – R)/(B + V + R)

  7. HB morphology and the B band

  8. V band

  9. I band

  10. K band

  11. Comparison with observations (I band)

  12. Two more clusters

  13. Still to do • Quantitative comparison of observed P-L relations with theory • Extension to systems beyond our own Galaxy

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