Theoretical growth rates, periods, and pulsation constants for long-period variables

Fox, Mark; Wood, P. R.

doi:10.1086/160160

Cited by 135 publications

(139 citation statements)

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“…The specific instability which causes AGB envelope ejection is still debated, but numerous previous studies exist (see, e.g., Paczyński & Ziółkowski 1968;Kutter & Sparks 1974;Tuchman et al 1978Tuchman et al , 1979Fox & Wood 1982;Wagenhuber & Weiss 1994;Han et al 1994;Soker 2008).…”

Section: Introductionmentioning

confidence: 99%

On the role of recombination in common-envelope ejections

Іванова

Justham

Podsiadlowski

2015

Monthly Notices of the Royal Astronomical Society

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The energy budget in common-envelope events (CEEs) is not well understood, with substantial uncertainty even over to what extent the recombination energy stored in ionised hydrogen and helium might be used to help envelope ejection. We investigate the reaction of a red-giant envelope to heating which mimics limiting cases of energy input provided by the orbital decay of a binary during a CEE, specifically during the post-plunge-in phase during which the spiral-in has been argued to occur on a time-scale longer than dynamical. We show that the outcome of such a CEE depends less on the total amount of energy by which the envelope is heated than on how rapidly the energy was transferred to the envelope and on where the envelope was heated. The envelope always becomes dynamically unstable before receiving net heat energy equal to the envelope's initial binding energy. We find two types of outcome, both of which likely lead to at least partial envelope ejection: "runaway" solutions in which the expansion of the radius becomes undeniably dynamical, and superficially "self-regulated" solutions, in which the expansion of the stellar radius stops but a significant fraction of the envelope becomes formally dynamically unstable. Almost the entire reservoir of initial helium recombination energy is used for envelope expansion. Hydrogen recombination is less energetically useful, but is nonetheless important for the development of the dynamical instabilities. However, this result requires the companion to have already plunged deep into the envelope; therefore this release of recombination energy does not help to explain wide post-common-envelope orbits.

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Section: Introductionmentioning

confidence: 99%

On the role of recombination in common-envelope ejections

Іванова

Justham

Podsiadlowski

2015

Monthly Notices of the Royal Astronomical Society

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“…Using the adiabatic oscillation code LOSC ([2]), we have computed radial and non-radial ( = 1, 2) oscillation frequencies for AGB envelope models ( [1]) for three masses (0.8, 1.5 and 2.0 M ) with a significant representation in the LMC population synthesis. The left panel of Figure 1 shows the period-luminosity (PL) diagram for a luminosity sequence of a 1.5 M envelope model.…”

Section: Methods and Resultsmentioning

confidence: 99%

Non-radial modes in AGB stars

Montalbán¹,

Trabucchi²,

Marigo³

et al. 2017

EPJ Web Conf.

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Abstract. The success of asteroseismology in characterising G-K giants has motivated the extension of the same techniques to stars after the central He-burning and M-giants. The latter have been usually studied only as radial pulsators; the presence, however, of fine-structure in the period-luminosity diagram of red variables in the Magellanic Clouds could result from the presence of non-radial oscillations, offering the potential of observational indexes based on non-radial oscillations also for luminous red giants. We present here the results of a first approach aiming to identify the origin of the sub-ridges in the sequence A of the LMC red variables. Method and resultsAfter the central H-and He-burning, the density contrast between the core and the envelope increases with luminosity, and these stellar regions become dynamically decoupled. Radial and non-radial modes are then strongly trapped in the envelope, and their oscillation frequencies are determined only by the physical properties of that region. This hypothesis is generally accepted for radial and quadrupole modes, but it does not always hold for dipole ones. We have verified its validity for dipole modes ( = 1) in 1.5 M AGB models, by computing = 1 frequency oscillations for complete and envelope models. These results are consistent with those by [3] for luminous RGB stars.Using the adiabatic oscillation code LOSC ([2]), we have computed radial and non-radial ( = 1, 2) oscillation frequencies for AGB envelope models ([1]) for three masses (0.8, 1.5 and 2.0 M ) with a significant representation in the LMC population synthesis. The left panel of Figure 1 shows the period-luminosity (PL) diagram for a luminosity sequence of a 1.5 M envelope model. Adiabatic computations do not allow to identify the dominant mode (P1), hence, we have considered all the possible theoretical period-pairs from the 6 modes closest to P max (period at maximum emission in the framework of stochastic oscillations). The results are shown in the right panel of Figure 1, a Petersen diagram where we plot the period ratios log(P2/P1) and log(P3/P1) (P1, P2 and P3 are the three observed periods for each star -black dots -in the LMC, with P1 being the dominant one) against log P1[W JK = 12] (the value of log P1 projected along sequence A, see [4] for details). While the sub-ridges at log(P2/P1) ∼ ±0.05 seem defined by the periods of = 1 and = 2 modes and their characterisation should require more detailed modelling, the sub-ridges at log(P2/P1) ∼ ±0.02 are completely determined by the period difference between = 0 and = 2 modes, and their location does not depend on total stellar mass, He-core mass, or chemical composition (O-or C-rich models).

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“…OH/IR stars tend not to be observable in the V-band, and are often classified as SR because the amplitude is only measured at K. Stars with higher C/O ratio show reduced abundances of oxygen-rich molecules, and can therefore also show lower amplitudes. The pulsation equation is given by: log P = 1.949 log R − 0.9 log M − 2.07 fundamental mode Wood 1990) log P = 1.5 log R − 0.5 log M + log Q first overtone (Fox & Wood 1982), (2.1) where in the latter case the pulsation constant Q ≈ 0.04; the period P is in days and the radius R and mass M are in solar units. Mira variables are fundamental-mode pulsators, whilst SR variables show overtone pulsations.…”

Section: Pulsationsmentioning

confidence: 99%

Mass loss on the Asymptotic Giant Branch

Zijlstra¹

2006

IAU

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Abstract. Mass loss on the Asymptotic Giant Branch provides the origin of planetary nebulae. This paper reviews several relevant aspects of AGB evolution: pulsation properties, mass loss formalisms and time variable mass loss, evidence for asymmetries on the AGB, binarity, ISM interaction, and mass loss at low metallicity. There is growing evidence that mass loss on the AGB is already asymmetric, but with spherically symmetric velocity fields. The origin of the rings may be in pulsational instabilities causing mass-loss variations on time scales of centuries.

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Theoretical growth rates, periods, and pulsation constants for long-period variables

Cited by 135 publications

References 0 publications

On the role of recombination in common-envelope ejections

On the role of recombination in common-envelope ejections

Non-radial modes in AGB stars

Mass loss on the Asymptotic Giant Branch

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