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

TL;DR

This work cross-matches J-VAR DR1 RR Lyrae with Gaia DR3 to derive periods and amplitudes in seven optical bands using the SDSS Multiband Template Library for template fitting. It demonstrates that J-VAR periods agree closely with Gaia, and that RR Lyrae amplitudes decrease with wavelength, following an exponential trend when normalized to the $r$-band amplitude. The analysis confirms robust RRab/RRc separation across all bands and shows that SDSS broadband templates adequately describe the medium and narrow J-VAR bands, including $J0395$, $J0515$, $J0660$, and $J0861$. The resulting J-VAR RR Lyrae catalog provides reliable pulsation parameters across 395–860 nm, enabling systematic multiwavelength pulsation studies and cross-survey comparisons with Gaia and ZTF, with potential for probing atmospheric dynamics and stellar evolution.

Abstract

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 $860~\text{nm}$.

Figures (7)

• Figure 1: Bailey Diagram: Density plot for period vs. amplitude distribution of RR Lyrae stars in Gaia DR3 Variable Star catalog using log-scaled color bins. The overplotted dots represent the $315$ J-VAR DR1 objects, with RRab (red), RRc (cyan), and RRd (purple) subtypes color-coded.
• Figure 2: Light curves: The figure shows phase-folded light curves for five example RR Lyrae in the J-VAR DR1 + Gaia DR3 catalog. A RR Lyrae star of RRc subtype (Upper Left panel) and four RR Lyrae stars of RRab subtype (Remaining panels) are shown. The unique identification numbers for objects in J-VAR DR1 are provided.
• Figure 3: Light curve analysis in J-VAR DR1 for two representative examples. Top panels: The light curve analysis by fitting the best-fitted templates. Middle panels: Residuals normalized by magnitude errors plotted against phase. Bottom panels: The Residuals plotted against sigma errors in magnitudes. A solid black line in the plot marks the zero reference point. The legends in the right of each plot describe the bands (e.g., $g$-band), the periods of the best-fitted templates (e.g., $0.65627$ d, also known as J-VAR periods), the number and band of the best-fitted template (e.g., $101g$), and the $\chi\textsuperscript{2}$ test (e.g., $1.00$). The J-VAR DR1 unique identification numbers are also provided.
• Figure 4: Bailey Diagram with J-VAR periods and J-VAR amplitudes. Left panel: $gri$ bands. Right panel: $J0395$, $J0515$, $J0660$, and $J0861$ bands.
• Figure 5: Normalized amplitudes vs. wavelength. The points represent the medians of the J-VAR amplitudes for each band normalized by that in the $r$-band. The figure also shows the Gaia$G$-band and the ZTF $g$ and $r$ bands (normalized by the J-VAR $r$-band) for comparison and were not included in the fit. The dashed black line indicates the exponential fit. Error bars correspond to the 25th ($p_{25}$) and 75th ($p_{75}$) percentiles. N denotes the number of valid amplitude ratios computed per band.