Variability in red supergiant stars: pulsations, long secondary periods and convection noise

By László L. Kiss, G. Szabó, T. Bedding. 2006

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We study the brightness variations of galactic red supergiant stars using long-term visual light curves collected by the American Association of Variable Star Observers (AAVSO) over the last century. The full sample contains 48 red semiregular or irregular variable stars, with a mean time-span of observations of 61 years. We determine periods and period variability from analyses of power density spectra and time-frequency distributions. We find two significant periods in 18 stars. Most of these periods fall into two disti nct groups, ranging from a few hundred to a few thousand days. Theoretical models imply fundamental, first and possibly second overtone mode pulsations for the shorter periods. Periods greater than 1000 days form a parallel period-luminosity relation that is similar to th e Long Secondary Periods of the Asymptotic Giant Branch stars. A number of individual power spectra shows a single mode resolved into multiple peaks under a Lorentzian envelope, which we interpret as evidence for stochastic oscillations, presumably caused by the interpl ay of convection and pulsations. We find a strong 1/f noise component in the power spectra that is remarkably similar in almost all stars of the sample. This behaviour fits the picture of irregu lar photometric variability caused by large convection cells, analogous to the granulation background seen in the Sun.

Subfields: Astronomy and Astrophysics, Education, Instrumentation

View Paper: https://www.semanticscholar.org/paper/1e14cbe07834ca8914bc8641a9c71f00d3d87389

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Citations in the corpus

The mass-loss rates of red supergiants and the de Jager prescription (2010, background): “Like for other mass-losing cool giants, atmospheric motions such as pulsation, convection and shocks occur (e.g. Kiss et al. 2006; Josselin & Plez 2007), and this may produce out-moving gas sufficiently cool for dust to form Then, radiation pressure on the grains may be sufficient to drive the…”
THE AGE AND MASS OF THE α HERCULIS TRIPLE-STAR SYSTEM FROM A MESA GRID OF ROTATING STARS WITH 1.3 ⩽ M/M☉ ⩽ 8.0 (2013, background): “Due to the observed Long Secondary Period (LSP, Kiss et al. 2006; Percy et al. 2001) of α1 Her, γ2 varies with the period of ∼ 1400 days; this can serve as an evidence for the pulsation origin of the LSP. 5.2.”
COMPREHENSIVE PHOTOMETRIC HISTORIES OF ALL KNOWN GALACTIC RECURRENT NOVAE (2009, background): “…in interacting binaries, both symbiotic and nonsymbiotic, both Miras and non-pulsating stars) have ubiquitous power law PDS to very low frequencies (Kiss et al. 2006; Stello et al. 2008; Templeton & Karovska 2009) which is identified with the convection cells on the surface (Antia et al. 1984;…”