The CoRoT discovery of a unique triple-mode cepheid in the galaxy

TL;DR

This paper reports the discovery of a unique triple-mode Cepheid in the Milky Way by CoRoT, exhibiting unusual period ratios and modes, providing insights into stellar pulsation and galactic structure.

Contribution

It presents the first identification of a triple-mode Cepheid with an unusual period ratio in our galaxy, expanding understanding of stellar pulsation modes.

Findings

Discovered a triple-mode Cepheid with unique period ratios

Identified the pulsation modes as radial overtones and possibly a nonradial mode

Located the star in the metal-rich outer arm of the Milky Way

Abstract

The exploitation of the CoRoT treasure of stars observed in the exoplanetary field allowed the detection of a unusual triple-mode Cepheid in the Milky Way, CoRoT 0223989566. The two modes with the largest amplitudes and period ratio of 0.80 are identified with the first (P1=1.29 d) and second (P2=1.03 d) radial overtones. The third period, which has the smallest amplitude but able to produce combination terms with the other two, is the longest one (P3=1.89 d). The ratio of 0.68 between the first-overtone period and the third period is the unusual feature. Its identification with the fundamental radial or a nonradial mode is discussed with respect to similar cases in the Magellanic Clouds. In both cases the period triplet and the respective ratios make the star unique in our Galaxy. The distance derived from the period-luminosity relation and the galactic coordinates put CoRoT~0223989566 in the metal-rich environment of the "outer arm" of the Milky Way.