Detection of Gravity Modes in RR Lyrae Stars

Abstract

We report the detection of gravity modes in RR Lyrae stars. Thanks to PAIX, the first Antarctica polar photometer. Unprecedented and uninterrupted U BV RI time-series photometric ground-based data are collected during 150 days from the highest plateau of Antarctica. PAIX light curve analyses reveal an even richer power spectrum with mixed modes in RR Lyrae stars. A nonlinear nature of several dominant peaks, showing lower and higher frequencies, occur around the dominant fundamental radial pressure mode. These lower frequencies and harmonics linearly interact with the dominant fundamental radial pressure mode and its second and third overtone pressure modes as well. Half-integer frequencies are also detected, likewise side peak structures demonstrating that HH puppis is a bona-fide Blazhko star. Fourier correlations are used to derive underlying physical characteristics for HH puppis. The most striking finding is the direct detection of gravity waves. We interpret the excitation mechanism of gravity waves in RR Lyrae stars by the penetrative convection driving mechanism. We demonstrate that RR Lyrae stars pulsation is excited by several distinct mechanisms, and hence RR Lyrae stars are simultaneously g modes and p modes pulsators. Our discoveries make RR Lyrae stars very challenging stellar objects, and provide their potential to undergo at the same time g modes and p modes towards an advancement of theory of stellar evolution and a better understanding of the Universe.

arXiv comment17 pages, 6 figures, accepted for publication in the Astrophysical Journal ApJ

References in corpus (25)

• Kepler Mission Design, Realized Photometric Performance, and Early Science
• The CoRoT satellite in flight : description and performance
• Gravity modes as a way to distinguish between hydrogen- and helium-burning red giant stars
• Initial Characteristics of Kepler Short Cadence Data
• SigSpec - I. Frequency- and Phase-Resolved Significance in Fourier Space
• The MACHO Project Large Magellanic Cloud variable star inventory. XI. Frequency analysis of the fundamental mode RR Lyrae stars
• On the Blazhko Effect in RR Lyrae Stars
• Fourier analysis of non-Blazhko ab-type RR Lyrae stars observed with the Kepler space telescope
• Pulsational M_V versus [Fe/H] relation(s) for globular cluster RR Lyrae variables
• Spectroscopic Comparison of Metal-Rich RRab Stars of the Galactic Field with Their Metal-Poor Counterparts
• Spectrum and amplitudes of internal gravity waves excited by penetrative convection in solar-type stars
• Long time-scale behavior of the Blazhko effect from rectified Kepler data
• The Metallicity Dependence of the Fourier Components of RR Lyrae Light Curves is the Oosterhoff/Arp/Preston Period Ratio Effect in Disguise
• On the Use of Field RR Lyrae as Galactic Probes. II. A new $\Delta$S calibration to estimate their metallicity
• First results on RR Lyrae stars with the TESS space telescope: untangling the connections between mode content, colors and distances
• An RR Lyrae family portrait: 33 stars observed in Pisces with K2-E2
• Discovery of a new group of double-periodic RR Lyrae stars in the OGLE-IV photometry
• The census of non-radial pulsation in first-overtone RR Lyrae stars of the OGLE Galactic bulge collection
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. I. Long-period stars with dominant radial fundamental mode
• Peculiar double-periodic pulsation in RR Lyrae stars of the OGLE collection. II. Short-period stars with dominant radial fundamental mode
• The Distance of the Large Magellanic Cloud Cluster NGC 1866
• The Axial Rotation and Variable Macroturbulence of RR Lyrae and Red Horizontal Branch Stars
• Turbulence generation by a shock wave interacting with a random density inhomogeneity field
• Finest light curve details, physical parameters, and period fluctuations of CoRoT RR Lyrae stars
• The additional-mode garden of RR Lyrae stars