Fundamental parameters of RR Lyrae stars from multicolour photometry and Kurucz atmospheric models -- II. Adaptation to double-mode stars

TL;DR

This study extends a photometric-hydrodynamic method to determine fundamental parameters of double-mode RR Lyrae stars using multicolour photometry, revealing detailed stellar properties and classifications.

Contribution

It adapts and applies a generalized method to analyze double-mode pulsating stars, incorporating ultraviolet data for accurate classification and parameter estimation.

Findings

GSC 4868-0831 is a subgiant pulsating in two radial modes.

V372 Ser is a giant star with properties similar to RRd stars.

Ultraviolet photometry is crucial for proper RR Lyrae classification.

Abstract

Our photometric-hydrodynamic method is generalized to determine fundamental parameters of multiperiodic radially pulsating stars. We report 302 UBV(RI)_C Johnson-Kron-Cousins observations of GSC 4868-0831. Using these and published photometric data of V372 Ser, their metallicity, reddening, distance, mass, radius, equilibrium luminosity, effective temperature are determined. The results underline the necessity of using multicolour photometry including an ultraviolet band to classify properly subgroups of RR Lyrae stars: our U observations could reveal that GSC 4868-0831 is a subgiant star pulsating in two radial modes, V372 Ser is a giant star with size and mass of an RRd star.