Radial Stellar Pulsation and Three-Dimensional Convection. Ii. Two-Dimensional Convection in Full Amplitude Radial Pulsation

Geroux, Chris M.; Deupree, R. G.

doi:10.1088/0004-637x/771/2/113

Cited by 16 publications

(6 citation statements)

References 47 publications

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“…Computed light curve morphology is in good agreement with observed RR Lyrae light curves, including the well known RR Lyrae phase discrepancy problem (Simon 1985). Recently, Geroux & Deupree (2013) implemented a two-dimensional (2D) radiation hydrodynamic code that simulates the interaction of radial pulsation and convection. The code is able to match the observed light curve shape near the red edge of the RR Lyrae instability strip the in HR diagram.…”

Section: Introductionsupporting

confidence: 62%

Dynamical structure of the pulsating atmosphere of RR Lyrae

Gillet¹,

Mauclaire²,

Lemoult³

et al. 2019

A&A

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Context. RRab stars are large amplitude pulsating stars in which the pulsation wave is a progressive wave. Consequently, strong shocks, stratification effects, and phase lag may exist between the variations associated with line profiles formed in different parts of the atmosphere, including the shock wake. The pulsation is associated with a large extension of the expanding atmosphere, and strong infalling motions are expected. Aims. The objective of this study is to provide a general overview of the dynamical structure of the atmosphere occurring over a typical pulsation cycle. Methods. We report new high-resolution observations with suitable time resolution of Hα and sodium lines in the brightest RR Lyrae star of the sky: RR Lyr (HD 182989). A detailed analysis of line profile variations over the whole pulsation cycle is performed to understand the dynamical structure of the atmosphere. Results. The main shock wave appears when it exits from the photosphere at ϕ 0.89, i.e., when the main Hα emission is observed. Whereas the acceleration phase of the shock is not observed, a significant deceleration of the shock front velocity is clearly present. The radiative stage of the shock wave is short: 4% of the pulsation period (0.892 < ϕ < 0.929). A Mach number M > 10 is required to get such a radiative shock. The sodium layer reaches its maximum expansion well before that of Hα (∆ϕ = 0.135). Thus, a rarefaction wave is induced between the Hα and sodium layers. A strong atmospheric compression occurring around ϕ = 0.36, which produces the third Hα emission, takes place in the highest part of the atmosphere. The region located lower in the atmosphere where the sodium line is formed is not involved. The amplification of gas turbulence seems mainly due to strong shock waves propagating in the atmosphere rather than to the global compression of the atmosphere caused by the pulsation. It has not yet been clearly established whether the microturbulence velocity increases or decreases with height in the atmosphere. Furthermore, it seems very probable that an interstellar component is visible within the sodium profile.

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Section: Introductionsupporting

confidence: 62%

Dynamical structure of the pulsating atmosphere of RR Lyrae

Gillet¹,

Mauclaire²,

Lemoult³

et al. 2019

A&A

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“…We make particular mention of RR Lyr, an RR0, which has been shown by Kepler to have small amplitude first overtone pulsations (Molnár et al 2012), a phenomenon perhaps connected to these mmRRs. Finally, theoretical work indicates that convection and viscous damping are the likely physical process that set the amplitudes of RR Lyrae variables (Kolláth et al 1998;Smolec & Moska-lik 2008;Geroux & Deupree 2013); mmRRs could be valuable in further developing this understanding.…”

Section: Discussionmentioning

confidence: 99%

Ultralow-amplitude RR Lyrae Stars in M4

Wallace

Hartman

Bakos

et al. 2019

ApJL

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We report evidence for a new class of variable star, which we dub millimagnitude RR Lyrae (mmRR). From K2 observations of the globular cluster M4, we find that out of 24 horizontal branch stars not previously known to be RR Lyrae variables, two show photometric variability with periods and shapes consistent with those of first overtone RR Lyrae variables. The variability of these two stars, however, have amplitudes of only one part in a thousand, which is ∼200 times smaller than for any RR Lyrae variable in the cluster, and much smaller than any known RR Lyrae variable generally. The periods and amplitudes are: 0.33190704 d with 1.0 mmag amplitude and 0.31673414 d with 0.3 mmag amplitude. The stars lie just outside the instability strip, one blueward and one redward. The star redward of the instability strip also exhibits significant multi-periodic variability at lower frequencies. We examine potential blend scenarios and argue that they are all either physically implausible or highly improbable. Stars such as these are likely to shed valuable light on many aspects of stellar physics, including the mechanism(s) that set amplitudes of RR Lyrae variables.

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“…The 2D simulation results can then be included in the 1D nonlinear stability computations by varying the (otherwise constant assumed) 1D convection parameters over the pulsation cycle according to the simulations. Hydrodynamical simulations of pulsations in classical variable stars were also conducted by Geroux and Deupree (2013). These are a few of the examples that point towards the direction in which this complex field of convection-pulsation interaction is heading.…”

Section: Brief Discussion and Prospectsmentioning

confidence: 99%

Interaction Between Convection and Pulsation

Houdek

Dupret

2015

Living Rev. Sol. Phys.

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This article reviews our current understanding of modelling convection dynamics in stars. Several semi-analytical time-dependent convection models have been proposed for pulsating one-dimensional stellar structures with different formulations for how the convective turbulent velocity field couples with the global stellar oscillations. In this review we put emphasis on two, widely used, time-dependent convection formulations for estimating pulsation properties in one-dimensional stellar models. Applications to pulsating stars are presented with results for oscillation properties, such as the effects of convection dynamics on the oscillation frequencies, or the stability of pulsation modes, in classical pulsators and in stars supporting solar-type oscillations. Article RevisionsLiving Reviews supports two ways of keeping its articles up-to-date:Fast-track revision. A fast-track revision provides the author with the opportunity to add short notices of current research results, trends and developments, or important publications to the article. A fast-track revision is refereed by the responsible subject editor. If an article has undergone a fast-track revision, a summary of changes will be listed here.Major update. A major update will include substantial changes and additions and is subject to full external refereeing. It is published with a new publication number.For detailed documentation of an article's evolution, please refer to the history document of the article's online version at http://dx

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Radial Stellar Pulsation and Three-Dimensional Convection. Ii. Two-Dimensional Convection in Full Amplitude Radial Pulsation

Cited by 16 publications

References 47 publications

Dynamical structure of the pulsating atmosphere of RR Lyrae

Dynamical structure of the pulsating atmosphere of RR Lyrae

Ultralow-amplitude RR Lyrae Stars in M4

Interaction Between Convection and Pulsation

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