Dynamical Stability and Habitability of the γ Cephei Binary‐Planetary System

Haghighipour, Nader

doi:10.1086/503351

Cited by 77 publications

(74 citation statements)

References 47 publications

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“…We assumed an edge-on configuration. This is an important restriction, since any inclination of the orbital plane of the binary would lead to much higher values of m B (see Hatzes et al 2003;Haghighipour 2006). Although both fits correspond to significantly different dynamical systems, they yield practically the same residuals: (χ 2 ν ) 1/2 = 1.98.…”

Section: Possible Orbital Solutions For γ-Cepheimentioning

confidence: 96%

“…It is then no surprise that this planetary system has caught the attention of several researchers over the past decade, and many dynamical and collisional studies may be found in the literature (e.g. Thébault et al 2004Thébault et al , 2006Haghighipour 2006;Verrier & Evans 2006;Tsukamoto & Makino 2007;Paardekooper et al 2008;Xie & Zhou 2008;Kley & Nelson 2008;Paardekooper & Leinhardt 2010).…”

Section: Introductionmentioning

confidence: 99%

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Secular dynamics of planetesimals in tight binary systems: application toγ-Cephei

Giuppone

Leiva

Correa-Otto

et al. 2011

A&A

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Context. The secular dynamics of small planetesimals in tight binary systems play a fundamental role in establishing the possibility of accretional collisions in such extreme cases. The most important secular parameters are the forced eccentricity and secular frequency, which depend on the initial conditions of the particles, as well as on the mass and orbital parameters of the secondary star. Aims. We construct a second-order theory (with respect to the masses) for the planar secular motion of small planetasimals and deduce new expressions for the forced eccentricity and secular frequency. We also reanalyze the radial velocity data available for γ-Cephei and present a series of orbital solutions leading to residuals compatible with the best fits. Finally, we discuss how different orbital configurations for γ-Cephei may affect the dynamics of small bodies in circumstellar motion. Methods. The secular theory is constructed using a Lie series perturbation scheme restricted to second order in the small parameter. The orbital fits were analyzed with a minimization code that employs a genetic algorithm for a preliminary solution plus a simulated annealing for the fine tuning. Results. For γ-Cephei, we find that the classical first-order expressions for the secular frequency and forced eccentricity lead to large inaccuracies ∼50% for semimajor axes larger than one tenth the orbital separation between the stellar components. Low eccentricities and/or masses reduce the importance of the second-order terms. The dynamics of small planetesimals only show a weak dependence with the orbital fits of the stellar components, and the same result is found including the effects of a nonlinear gas drag. Thus, the possibility of planetary formation in this binary system largely appears insensitive to the orbital fits adopted for the stellar components, and any future alterations in the system parameters (due to new observations) should not change this picture. Finally, we show that planetesimals migrating because of gas drag may be trapped in mean-motion resonances with the binary, even though the migration is divergent.

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Section: Possible Orbital Solutions For γ-Cepheimentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Secular dynamics of planetesimals in tight binary systems: application toγ-Cephei

Giuppone

Leiva

Correa-Otto

et al. 2011

A&A

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“…Several authors have studied planet formation and migration in the γ Cephei system (Dvorak et al 2004;Thébault et al 2004;Haghighipour 2006;Verrier & Evans 2006;Kley & Nelson 2008;Jang-Condell et al 2008;Paardekooper et al 2008;Xie & Zhou 2008;Paardekooper & Leinhardt 2010). We also consider the parameters of this binary (values taken from Torres 2007) as a starting point in our study.…”

Section: Introductionmentioning

confidence: 99%

The first stages of planet formation in binary systems: how far can dust coagulation proceed?

Zsom

Sándor

Dullemond

2011

A&A

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Context. On the basis of current theoretical models, giant planets can form via gravitational instability or core accretion. The terrestrial planets are "failed cores" in the core accretion paradigm that do not evolve into gas giants. Planets residing in binary systems place strong constraints on planet formation theory as any model must work in binary systems too, in spite of the strong perturbations from the secondary star. Aims. We examine the first phase of the core accretion model, namely the dust growth/fragmentation in binary systems. In our model, a gas and dust disk exists around the primary star and is perturbed by the secondary. We study the effects of a secondary with/without eccentricity on the dust population to determine the sizes the aggregates can reach and how that compares to the dust population in disks around single stars. Methods. We solve the equation of motion of dust aggregates including gas drag and gravitational forces from both stars, as well as the hydrodynamical equations for the gas disk. We determine the velocity of these particles relative to the gas (or relative to micronsized, well-coupled dust particles) and construct a collision model with growth and erosion. Particles below the critical fragmentation velocity increase in mass by sweeping up the small dust population; particles above this critical speed are eroded by collisions with the small dust population. We use this model to determine the sizes that aggregates can reach in the disk, in addition to the equilibrium mass and stopping time distributions between growth and erosion. Results. We find that the secondary star has two effects on the dust population: 1. the disk is truncated because of the presence of the secondary star, and the maximum mass of the particles is lower in lower gas densities. This effect is predominant in the outer disk; 2. the perturbation of the secondary increases the eccentricity of the gas disk, which in turn increases the relative velocity between the dust and the gas. Hence the maximum particle sizes are further decreased. The second effect of the secondary influences the entire disk. Coagulation is efficiently reduced even at the very inner parts of the disk. The average mass of the particles is lower by four orders of magnitude (as a consequence, the stopping time is shorter by one order of magnitude) in disks around binary systems than for dust in disks around single stars.

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“…Among the currently known extrasolar planet-hosting stars, approximately 20% are members of binaries or multiple systems (Haghighipour 2006). Nearly all of the planets in these systems revolve around only one of the stars.…”

Section: Introductionmentioning

confidence: 99%

Microlensing Search for Planets with Two Simultaneously Rising Suns

Han

2008

ApJ

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Among more than 200 extrasolar planet candidates discovered to date, there is no known planet orbiting around normal binary stars. In this Letter, we demonstrate that microlensing is a technique that can detect such planets. Microlensing discoveries of these planets are possible because the planet and host binary stars produce perturbations at a common region around center of mass of the binary stars and thus the signatures of both planet and binary can be detected in the light curves of high-magnification microlensing events. The ranges of the planetary and binary separations of systems for optimal detection vary depending on the planet mass. For a Jupiter-mass planet, we find that high detection efficiency is expected for planets located in the range of ∼1-5 AU from the binary stars which are separated by ∼0.15-0.5 AU.

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Dynamical Stability and Habitability of the γ Cephei Binary‐Planetary System

Cited by 77 publications

References 47 publications

Secular dynamics of planetesimals in tight binary systems: application toγ-Cephei

Secular dynamics of planetesimals in tight binary systems: application toγ-Cephei

The first stages of planet formation in binary systems: how far can dust coagulation proceed?

Microlensing Search for Planets with Two Simultaneously Rising Suns

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