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

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.

arXiv commentPublished as ApJ Letter

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• Cepheids with the eyes of photometric space telescopes
• Exploring Low-Amplitude Variability in First Overtone Cepheids with TESS
• The VELOCE modulation zoo III. Detecting additional pulsation modes in optical spectra of classical Cepheids using semi-partial distance correlation periodograms