Preliminary results for RR Lyrae stars and Classical Cepheids from the Vista Magellanic Cloud (VMC) Survey

TL;DR

The VMC survey provides high-quality $K_S$-band light curves of RR Lyrae stars and Cepheids in the Magellanic Clouds, enabling precise distance measurements and 3D mapping of the system.

Contribution

This study presents the first $K_S$-band light curves for Magellanic Cloud variables, improving the $PLK_S$ relations with lower scatter and higher accuracy.

Findings

High-quality $K_S$-band light curves for RR Lyrae and Cepheids.

Derived $PLK_S$ relations with smaller scatter than previous studies.

Good agreement of new relations with literature data.

Abstract

The Vista Magellanic Cloud (VMC, PI M.R. Cioni) survey is collecting $K_S$-band time series photometry of the system formed by the two Magellanic Clouds (MC) and the "bridge" that connects them. These data are used to build $K_S$-band light curves of the MC RR Lyrae stars and Classical Cepheids and determine absolute distances and the 3D geometry of the whole system using the $K$-band period luminosity ($PLK_S$), the period - luminosity - color ($PLC$) and the Wesenhiet relations applicable to these types of variables. As an example of the survey potential we present results from the VMC observations of two fields centered respectively on the South Ecliptic Pole and the 30 Doradus star forming region of the Large Magellanic Cloud. The VMC $K_S$-band light curves of the RR Lyrae stars in these two regions have very good photometric quality with typical errors for the individual data points in the range of $\sim$ 0.02 to 0.05 mag. The Cepheids have excellent light curves (typical errors of $\sim$ 0.01 mag). The average $K_S$ magnitudes derived for both types of variables were used to derive $PLK_S$ relations that are in general good agreement within the errors with the literature data, and show a smaller scatter than previous studies.