Astronomy Seminar

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Date/Time:Friday, 07 Nov 2014 at 4:10 pm
Location:3 Physics
Phone:515-294-5440
Channel:College of Liberal Arts and Sciences
Categories:Lectures
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Revealing stability in the instability strip: a mid-infrared period-luminosity relation for M4 (Jill Neeley, Iowa State University)

Accurate distances are among the most important measurements in astronomy, yet we still lack a self consistent distance scale to galactic globular clusters (GGCs). While distances have been measured using a variety of methods, each of them are valid for only a subset of GGCs. As part of the Carnegie RR Lyrae Program, we aim to resolve this by providing a calibration of the period-luminosity (PL) relation for RR Lyrae stars in the mid infrared (MIR) wavelengths. Advantages of working in the MIR include a reduced effect of extinction, lower amplitude, and a significantly smaller intrinsic scatter of the PL relation. We have conducted a survey at 3.6 and 4.5 ?m of 31 GGCs using the Infrared Array Camera (IRAC) onboard Spitzer Space Telescope. In this talk, I will discuss the analysis and new distance determination of M4, the closest GGC.