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We present infrared JHK time series photometry of the variable star RR Lyr, that allow us to construct the first complete and accurate infrared light curves for this star. The derived mean magnitudes are <J>=6.74 +/- 0.02, <H>=6.60 +/- 0.03 and <K>=6.50 +/- 0.02. The <K> magnitude is used to estimate the reddening, the mass, the mean luminosity and temperature of this variable star. The use of these RR Lyr data provide a more accurate absolute calibration of the P-L_K-[Fe/H] relation, and a distance modulus (m-M)_0=18.48 +/- 0.11 to the globular cluster Reticulum in the LMC.
We report here on two types of cyclic variations that can be observed in the periods of RR Lyr stars, i.e., the Blazhko and the light-time effects. The former has been investigated by studying the amplitude variations recorded in RR Lyr itself, first
We have obtained the most extensive and most accurate photometric data of a Blazhko variable MW Lyr during the 2006-2007 observing seasons. The data within each 0.05 phase bin of the modulation period (P_m=1/f_m) cover the entire light cycle of the p
We present newly-calibrated period-$phi_{31}$-[Fe/H] relations for fundamental mode RR Lyrae stars in the optical and, for the first time, mid-infrared. This works calibration dataset provides the largest and most comprehensive span of parameter spac
This paper provides a progress report on a collaborative program at the Las Campanas and Cerro Tololo Observatories to observe the near-IR light curves of Type Ia supernovae. We discuss how the morphologies of the JHK light curves change as a functio
The so-called H$alpha$ third emission occurs around pulsation phase $varphi$=0.30. It has been observed for the first time in 2011 in some RR Lyrae stars. The emission intensity is very weak, and its profile is a tiny persistent hump in the red side-