J-VAR: Analysis of RR Lyrae light curves in seven optical bands

Context:RR Lyrae stars, with their accurate period and amplitude measurements, constrain stellar evolution and map Galactic structure. The Javalambre VARiability (J-VAR) survey is the time-domain extension of the Javalambre Photometric Local Universe survey, which provides time-series data across seven optical bands, including $gri$ and four medium and narrow bands. Aims: Our goal is to construct and analyze light curves for RR Lyrae stars identified in the J-VAR's first data release using the \textit{Gaia} third data release (DR3) Variable Stars catalog as a reference. Methods: The light curves of $315$ RR Lyrae were analyzed by fitting templates from the Sloan Digital Sky Survey Multiband Template Library. The periods and amplitudes for the seven bands in J-VAR were independently obtained from the best-fitted templates. Results: The J-VAR periods show strong agreement with \textit{Gaia} DR3 values. The Bailey diagram for each J-VAR filter shows larger pulsation amplitudes at bluer wavelengths. Amplitudes, after normalizing by the $r$-band amplitude, show an exponential trend, with the bluer J-VAR filter centered at $395~\text{nm}$ having twice the amplitude of the reddest J-VAR passband at $861~\text{nm}$. The normalized amplitudes of the RR Lyrae stars from {\it Gaia} and the Zwicky Transient Facility are consistent with the J-VAR trend. Finally, the SDSS templates derived from broadbands also provide a proper description for the medium and narrow band light curves. Conclusions: The J-VAR RR Lyrae catalog offers reliable pulsation parameters and light curves in seven optical filters, allowing the systematic study of amplitude trends from $395~\text{nm}$ to $860~\text{nm}$.