The spectral Petersen diagram as a new tool to map pulsation modes in variable stars

TL;DR

The paper introduces the spectral Petersen diagram, a novel method that visualizes all pulsation signals in variable stars, enhancing the analysis of their pulsation modes beyond traditional techniques.

Contribution

It presents the spectral Petersen diagram, allowing comprehensive mapping of pulsation modes regardless of their strength or multiplicity, and enables stacking of light curves for improved signal detection.

Findings

Reveals detailed pulsation mode structures in variable stars.

Allows analysis of signals below traditional noise thresholds.

Facilitates better constraints on stellar pulsation models.

Abstract

Additional pulsation modes have been discovered in many Cepheids, RR Lyrae, and other variable stars. Fourier transforms are used to find, fit and subtract the main pulsation period and its harmonics to reveal additional modes. Commonly, for every star, the strongest of these modes is presented in a "Petersen diagram", where the shorter-to-longer period ratio is plotted against the longer period. This diagram discards the information about temporal variations, multiple pulsation modes, and signals which are below some chosen signal to noise threshold. I here present a new tool to map pulsation modes in variable stars, dubbed the "spectral Petersen diagram". It shows all signals, irrespective of their multiplicity or significance. Many (thousands) of light curves can be stacked to improve the signal to noise ratio and reveal unprecedented detail about the pulsation mode space. This tool is useful to constraint the parameters of variable star models.