A Study of RR1 Light Curve Modulation in OGLE-III Bulge Time-series (Abstract)

Volume 42 number 1 (2014)

Douglas L. Welch

McMaster University, 100 Melville St., Dundas, Ontario L9H 2A3, Canada; welch@physics.mcmaster.ca

Abstract

(Abstract only) We report the preliminary results of our study of lightcurve modulation in a sample of 493 RR1 variables from the OGLE-III survey of galactic bulge fields. Each object in this list has 1,500 or more I-band observations. We have located a “modulated-Blazhko” RR1 variable, OGLE-BLG-RRLYR-03825, which is similar in many respects to LS Her, a galactic field RR1 star. OGLE-BLG-RRLYR-03825’s photometric period is 0.2774114 d and it has a Blazhko period of 16.469 d which is, itself, modulated with a period of 339.2 d. Using an application of the “sequential CLEANest” method, we find that 169 of the 493 RR1 lightcurves examined show a detectable peak within the amplitude spectrum near 0.63 times the photometric period. Our finding extends the detection of such a period ratio in the four known RR1 stars in the Kepler field by Moskalik et al. (2012). We discuss how the appearance of this apparently new mode correlates with photometric (first overtone) period in this sample.