AAS 207th Meeting, 8-12 January 2006
Session 122 Variable Stars
Poster, Wednesday, 9:20am-6:30pm, January 11, 2006, Exhibit Hall

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[122.04] Crowding Corrections for First Overtone RR Lyrae Variables in the LMC

C. M. Clement, x. Xu, A. V. Muzzin (University of Toronto)

The high density of stars near the bar of the Large Magellanic Cloud (LMC) makes crowding a major source of uncertainty in estimating the apparent magnitudes of RR Lyrae variables. A commonly used technique to correct for this effect is to perform artificial star tests. However, these are not completely effective because they lead to general corrections based on density (i.e. the number of stars per square arcminute). As a result, the same correction is applied to a sample of stars even though the individual stars may not all be subject to the same amount of crowding.

Our study investigates a new method for identifying crowded RR1 (first overtone RR Lyrae) variables based on the period and amplitude of their light curves. Applying this new method, we obtain an LMC distance modulus of 18.46 ± 0.08 which improves the 10% error of our previous study (Alcock et al. 2004, AJ 127, 334) to a 4% error.

Support from Science and Engineering Research Canada (NSERC) is gratefully acknowledged.

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