From Rubin-LSST time-series data to stellar properties: the model fitting technique

LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms From Rubin-LSST time-series data to stellar properties: the model fitting technique Marcella Marconi, Roberto Molinaro, Giulia De Somma, Vincenzo Ripepi, Silvio Leccia, Ilaria Musella, Teresa Sicignano (SSM, ESO) , Erasmo Trentin, Massimiliano Gatto INAF-Osservatorio Astronomico di Capodimonte LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Outline ● Recently developed theoretical scenario for Classical Cepheids, RR Lyrae and Type II Cepheids in the Rubin-LSST filters → derived metal dependent Period-Luminosity and Period-Wesenheit relations. ● The model-fitting technique to reproduce multi-filter light curves and pulsational velocity variations → a recently published application to Gaia data. ● The perspectives of application to Rubin-LSST time-series data for Cepheids and RR Lyrae and other classes of pulsating stars. LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Recently developed theoretical scenario for pulsating stars in the Rubin-LSST filters Model predictions based on nonlinear convective hydrocodes allow us to derive light curves in different photometric bands and in turn mean magnitudes and colors that, together with periods, are the main ingredients to build PL, PLC and PW relations. We derived metal-dependent PL and PW relationships in the Rubin-LSST bands for RR Lyrae, Classical and Type II Cepheids. Marconi, M., et al. 2022, ApJ, New Theoretical Period-Luminosity-Metallicity Relations for RR Lyrae in the Rubin-LSST Filters, 934, 1, 29 De Somma, G. et al. 2024, MNRAS, Classical Cepheid pulsation properties in the Rubin-LSST filters, 528, 4, 6637 Marconi, M., et al. 2025, A&A, New theoretical predictions on T2Cs: towards a self consistent Pop. II distance scale, in press LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of theoretical light curves in the Rubin-LSST filters RR Lyrae Cepheids LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of theoretical light curves in the Rubin-LSST filters Mean magnitudes and colors in the Rubin-LSST filters LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of theoretical light curves in the Rubin-LSST filters Mean magnitudes and colors in the Rubin-LSST filters Rubin-LSST PL and PW relations LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Recently developed theoretical NIR PLZ for RR Lyrae Marconi et al. 2022 ApJ Metallicity effect on the zero-point r i z y LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Recently developed theoretical PW(Z) and CC(Z) for RRL Marconi et al. 2022 ApJ u,g u,r g,r g,i i,z g,y LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Recently developed theoretical PW(Z) and CC(Z) for RRL Marconi et al. 2022 ApJ u,g u,r g,r g,r i,z g,y Minimum metallicity effect ! LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms The model-fitting technique to reproduce multi-filter light curves and pulsational velocity variations A sample of 46 Classical Cepheids with precise photometric and radial velocity data from Gaia DR3 was analyzed and complementary spectroscopic metallicity measurements by Trentin et al. (2024) Molinaro et al. 2025, A&A Several criteria were considered: ● the widest possible coverage of the expected period range for CCs; ●well-sampled light and radial velocity curves in phase; ● sufficiently accurate parallaxes (σϖ/ϖ < 50%); ● metallicities obtained through recent high-resolution spectroscopy Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms The model-fitting technique to reproduce multi-filter light curves and pulsational velocity variations Molinaro et al. 2025, A&A Model fitting was conducted by directly comparing predicted and observed variations in Gaia G, GBP, and GRP light curves, as well as radial velocity time series, for the various metal abundances. i) Transformation of the bolometric magnitude light curves of the models in the Gaia photometric system (G, GBP, GRP). ii) Fit of the model light curves (in absolute magnitude) to observations is achieved by a magnitude shift (δmag) and a small fine tune of the phase (δϕ), such that the residuals attain the minimum value. Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms The model-fitting technique to reproduce multi-filter light curves and pulsational velocity variations Molinaro et al. 2025, A&A Model fitting was conducted by directly comparing predicted and observed variations in Gaia G, GBP, and GRP light curves, as well as radial velocity time series, for the various metal abundances. i) Transformation of the bolometric magnitude light curves of the models in the Gaia photometric system (G, GBP, GRP). ii) Fit of the model light curves (in absolute magnitude) to observations is achieved by a magnitude shift (δmag) and a small fine tune of the phase (δϕ), such that the residuals attain the minimum value. iii) Fit of the model pulsational velocity to observations, apart from a rigid shift along the velocity axis (δVel) and a small fine tune of the phase (δϕ), includes a stretch factor (p-factor) of the theoretical curve, in order to match the observed peak-to-peak amplitude. Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms The model-fitting technique to reproduce multi-filter light curves and pulsational velocity variations Molinaro et al. 2025, A&A Model fitting was conducted by directly comparing predicted and observed variations in Gaia G, GBP, and GRP light curves, as well as radial velocity time series, for the various metal abundances. i) Transformation of the bolometric magnitude light curves of the models in the Gaia photometric system (G, GBP, GRP). ii) Fit of the model light curves (in absolute magnitude) to observations is achieved by a magnitude shift (δmag) and a small fine tune of the phase (δϕ), such that the residuals attain the minimum value. iii) Fit of the model pulsational velocity to observations, apart from a rigid shift along the velocity axis (δVel) and a small fine tune of the phase (δϕ), includes a stretch factor (p-factor) of the theoretical curve, in order to match the observed peak-to-peak amplitude. iv) Bootstrap simulations are used to repeat steps ii) and iii) many times Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of best fit models Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of best fit models Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of best fit models Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of best fit models Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of best fit models Molinaro et al. 2025, A&A LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Some examples of best fit models Molinaro et al. 2025, A&A Masses, luminosities, effective temperatures, mean magnitudes and colors, distances (!) LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Model fitting of Rubin-LSST multi-filter light curves: an example of our very preliminary results for the RRL Gaia DR3 4831519899384690944 Rubin-LSST data fitted with nonlinear pulsation models. Very preliminary estimate of M, L, Te, Z and individual distance modulus. Inferred parallax (0.04 mas) in agreement with Gaia but large Gaia error. LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Model fitting of Rubin-LSST multi-filter light curves Also in connection with in-kind contribution S8 (see Musella’s talk), we plan to develop an advanced interactive model dataset based on the computation of nonlinear convective pulsation models These models will be produced using both Stellingwerf and MESA RSP (see Deka’s talk) codes → the first extended database of pulsation models available to the community Software tools, Monte-Carlo and/or multi-dimensional interpolation techniques, will be developed to match observed variations for huge numbers of Rubin-LSST pulsators, with a refined model fitting technique → luminosities, temperatures, masses, chemical abundances and distances for all the investigated stars from multi-filter light (and radial velocity) curves. LSST@Europe7 | Poznań, Poland | September 15th-19th, 2025 Glossary & Acronyms Conclusions ● A new theoretical scenario in the Rubin-LSST filters has been developed for various classes of pulsating stars on the basis of nonlinear convective pulsation models. ● These models allow a successful model-fitting of light and radial velocity curves (see Gaia’s case) ● In this context, while waiting for Rubin-LSST multi-filter light curves and in connection with the in-kind contribution S8, we are developing an advanced version of the model-fitting technique, able to match observed variations for huge numbers of Rubin-LSST pulsators.