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Cepheid Variables Key components of the distance ladder

Ultra Long Period Cepheids : An Intermediate Stage Between Classical Cepheids and Long Period Variables?. Scott Lucchini 1 , Chow- Choong Ngeow 2 , Shashi Kanbur 3 1 University of Rochester, Rochester, NY 2 National Central University, Jhongli , Taiwan 3 SUNY: Oswego, Oswego, NY.

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Cepheid Variables Key components of the distance ladder

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  1. Ultra Long Period Cepheids: An Intermediate Stage Between Classical Cepheids and Long Period Variables? Scott Lucchini1, Chow-Choong Ngeow2, Shashi Kanbur3 1University of Rochester, Rochester, NY 2National Central University, Jhongli, Taiwan 3SUNY: Oswego, Oswego, NY • Cepheid Variables • Key components of the distance ladder • Link between direct measurement techniques (parallax) and standard candles (supernovae) • Well-defined PL relation • Ultra Long Period Cepheids (ULPCs) • ULPCs = Fundamental Mode Cepheids with Periods > 80 days • Why ULPCs? • PL relation says stars with longer periods are brighter. • Therefore, we can see them from farther away, thus increasing the distance scale. • Bird et al (2009) • Studied 18 ULPCs from 6 galaxies • Found a flatter PL relation for the ULPCs when compared with SMC Classical Cepheids. • No one has studied the light curves or the evolutionary status of the ULPCs. • Are ULPCs really a sub-class of Cepheids? Or are they an intermediary, evolutionary stage between Classical Cepheids and Miras? • Analysis • For the Fourier parameters, the ULPCs seem to be more consistent with the Miras • For the PL relations, the ULPCs seem to be more consistent with the Classical Cepheids • Promising that the ULPCs aren’t always associated with one group • For the PC plot, the ULPCs seem to be aligned with both the Classical Cepheids and the Miras • Data • ULPCs • Bird’s data – 17 stars from 6 galaxies • We acquired additional data from Freedman et al (1985) and Martin and Warren (1979) • OGLE-III • Fundamental mode Classical Cepheids • LMC and SMC • Mira variables • LMC • Interstellar Reddening • Haschke et al (2011) • Used the “red clump” technique for the LMC and SMC • Conclusions • The ULPCs do seem to line up with the Classical Cepheids and the Miras. • But, the error bars are large and we don’t have enough ULPC stars Fourier Analysis References Bird J. et al, 2009, ApJ, 695, 874 Freedman W. L. et al, 1985, ApJ, 59, 311 Haschke R. et al, 2011, ApJ, 141, 158 Martin W. L. and Warren P. R., 1979, S. African Astro. Obsv. Circulars, 4, 98 Background Image: http://wallpaper-s.org/49_~_Sculpting_a_Galaxy_in_Orion_Nebula_%28M42%29.htm

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