The soundtrack of RR Lyrae in Omega Cen at high-frequency

TL;DR

This study presents high-frequency, multi-band photometric observations of RR Lyrae stars in Omega Cen, revealing detailed pulsation phases and demonstrating the capability of ULTRACAM for rapid, precise stellar variability studies.

Contribution

First high-frequency sampling of RR Lyrae stars in multiple bands in Omega Cen, enabling detailed analysis of pulsation phases with ULTRACAM.

Findings

Detected detailed pulsation phases of RR Lyrae stars

Sampled light curves every 15 seconds in multiple bands

Identified various types of variable stars in the cluster

Abstract

We present preliminary Sloan u',g'-band light curves for a sample of known RR Lyrae variables in the Galactic globular cluster Omega Cen. Results are based on the partial reduction of multi-band time series photometric data collected during six consecutive nights with the visitor instrument ULTRACAM mounted on the New Technology Telescope (La Silla, ESO). This facility allowed us to simultaneously observe in three different bands (Sloan u',g',r') a field of view of about 6x6 arcminutes. The telescope and the good seeing conditions allowed us to sample the light curves every 15 seconds. We ended up with a data set of about 6,000 images per night per filter, for a total of more than 200,000 images of the selected field. This data set allowed us to detect different kind of variables, such as RR-Lyraes, SX Phoenicis, eclipsing binaries, semi-regulars. More importantly, we were able for the first time to sample at high-frequency cluster RR Lyraes in the u',g'-band and to show in detail the pulsation phases across the dip located along the rising branch of RR-Lyraes.