Planet formation in binary stars

AbstractAs of today more than 30 planetary systems have been discovered in binary stars. In all cases the configuration is circumstellar, where the planets orbit around one of the stars. The formation process of planets in binary stars is more difficult than around single stars due to the gravitational action of the companion. An overview of the research done in this field will be given. The dynamical influence that a secondary companion has on a circumstellar disk, and how this affects the planet formation process in this challenging environment will be summarized. Finally, new fully hydrodynamical simulations of protoplanets embedded in disks residing in a binary star will be presented. Applications with respect to the planet orbiting the primary in the system γ Cephei will be presented.

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The fate of binary stars hosting planets upon interaction with Sgr A* black hole

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa1561 ◽

2020 ◽

Vol 496 (2) ◽

pp. 1545-1553

Author(s):

R Capuzzo-Dolcetta ◽

N Davari

Keyword(s):

Black Hole ◽

High Precision ◽

Binary Stars ◽

Binary Star ◽

Planetary Systems ◽

The Other ◽

Supermassive Black Hole ◽

Massive Object ◽

Close Interaction ◽

Sgr A

ABSTRACT Our Galaxy hosts a very massive object at its centre, often referred to as the supermassive black hole Sgr A*. Its gravitational tidal field is so intense that it can strip apart a binary star passing its vicinity and accelerate one of the components of the binary as hypervelocity star (HVS) and grab the other star as S-star. Taking into consideration that many binary star systems are known to host planets, in this paper we aim to broaden the study of the close interaction of binary stars and their planetary systems with Sgr A* massive object. Results are obtained via a high-precision N-body code including post-Newtonian approximation. We quantify the likelihood of capture and ejection of stars and planets after interaction with Sgr A*, finding that the fraction of stars captured around it is about three times that of the planets (∼49.4 per cent versus ∼14.5 per cent) and the fraction of hypervelocity planet ejection is about twice that of HVSs (∼21.7 per cent versus ∼9.0 per cent). The actual possibility of observational counterparts deserves further investigation.

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Habitable planet formation in extreme planetary systems: systems with multiple stars and/or multiple planets

Proceedings of the International Astronomical Union ◽

10.1017/s1743921308016773 ◽

2007 ◽

Vol 3 (S249) ◽

pp. 319-324

Author(s):

Nader Haghighipour

Keyword(s):

Binary Stars ◽

Binary Systems ◽

Planet Formation ◽

Planetary Systems ◽

Dynamical Evolution ◽

Giant Planets ◽

Habitable Planets ◽

Multiple Stars ◽

Habitable Zones ◽

Habitable Planet

AbstractUnderstanding the formation and dynamical evolution of habitable planets in extrasolar planetary systems is a challenging task. In this respect, systems with multiple giant planets and/or multiple stars present special complications. The formation of habitable planets in these environments is strongly affected by the dynamics of their giant planets and/or their stellar companions. These objects have profound effects on the structure of the disk of planetesimals and protoplanetary objects in which terrestrial-class planets are formed. To what extent the current theories of planet formation can be applied to such “extreme” planetary systems depends on the dynamical characteristics of their planets and/or their binary stars. In this paper, I present the results of a study of the possibility of the existence of Earth-like objects in systems with multiple giant planets (namely υ Andromedae, 47 UMa, GJ 876, and 55 Cnc) and discuss the dynamics of the newly discovered Neptune-sized object in 55 Cnc system. I will also review habitable planet formation in binary systems and present the results of a systematic search of the parameter-space for which Earth-like objects can form and maintain long-term stable orbits in the habitable zones of binary stars.

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Detailed elemental abundances of binary stars: Searching for signatures of planet formation and atomic diffusion

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stab2471 ◽

2021 ◽

Author(s):

Fan Liu ◽

Bertram Bitsch ◽

Martin Asplund ◽

Bei-Bei Liu ◽

Michael T Murphy ◽

...

Keyword(s):

Binary Stars ◽

Binary Systems ◽

Planet Formation ◽

Binary Star ◽

The Other ◽

Atomic Diffusion ◽

Element Abundance ◽

Condensation Temperature ◽

Elemental Abundances ◽

Abundance Patterns

Abstract Binary star systems are assumed to be co-natal and coeval, thus to have identical chemical composition. In this work we aim to test the hypothesis that there is a connection between observed element abundance patterns and the formation of planets using binary stars. Moreover, we also want to test how atomic diffusion might influence the observed abundance patterns. We conduct a strictly line-by-line differential chemical abundance analysis of 7 binary systems. Stellar atmospheric parameters and elemental abundances are obtained with extremely high precision (< 3.5%) using the high quality spectra from VLT/UVES and Keck/HIRES. We find that 4 of 7 binary systems show subtle abundance differences (0.01 - 0.03 dex) without clear correlations with the condensation temperature, including two planet-hosting pairs. The other 3 binary systems exhibit similar degree of abundance differences correlating with the condensation temperature. We do not find any clear relation between the abundance differences and the occurrence of known planets in our systems. Instead, the overall abundance offsets observed in the binary systems (4 of 7) could be due to the effects of atomic diffusion. Although giant planet formation does not necessarily imprint chemical signatures onto the host star, the differences in the observed abundance trends with condensation temperature, on the other hand, are likely associated with diverse histories of planet formation (e.g., formation location). Furthermore, we find a weak correlation between abundance differences and binary separation, which may provide a new constraint on the formation of binary systems.

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Pairwise tidal equilibrium states and the architecture of extrasolar planetary systems

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/stz1832 ◽

2019 ◽

Vol 488 (1) ◽

pp. 1446-1461 ◽

Cited By ~ 2

Author(s):

Fred C Adams

Keyword(s):

Formation Process ◽

Planet Formation ◽

Energy State ◽

Minimum Energy ◽

Variable Mass ◽

Planetary Systems ◽

Equilibrium States ◽

Circular Orbits ◽

Adjacent Pair ◽

Minimum Energy State

ABSTRACT Current observations indicate that the planet formation process often produces multiple planet systems with nearly circular orbits, regular spacing, a narrow range of inclination angles, and similar planetary masses of order mp ∼ 10 M⊕. Motivated by the observational sample, this paper determines the tidal equilibrium states for this class of extrasolar planetary systems. We start by considering two-planet systems with fixed orbital spacing and variable mass ratios. The basic conjecture explored in this paper is that the planet formation process will act to distribute planetary masses in order to achieve a minimum energy state. The resulting minimum energy configuration – subject to the constraint of constant angular momentum – corresponds to circular orbits confined to a plane, with nearly equal planetary masses (as observed). We then generalize the treatment to include multiple planet systems, where each adjacent pair of planets attains its (local) tidal equilibrium state. The properties of observed planetary systems are close to those expected from this pairwise equilibrium configuration. In contrast, observed systems do not reside in a global minimum energy state. Both the equilibrium states of this paper and observed multiplanet systems, with planets of nearly equal mass on regularly spaced orbits, have an effective surface density of the form σ ∝ r−2, much steeper than most disc models.

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The Structure and Evolution of Protoplanetary Disks: an Infrared and Submillimeter View

Proceedings of the International Astronomical Union ◽

10.1017/s1743921315006249 ◽

2015 ◽

Vol 10 (S314) ◽

pp. 128-134

Author(s):

Lucas A. Cieza

Keyword(s):

Formation Process ◽

Extrasolar Planets ◽

Planet Formation ◽

Planetary Systems ◽

Protoplanetary Disks ◽

Circumstellar Disks ◽

Submillimeter Wavelength ◽

High Incidence ◽

Near Future ◽

Very High

AbstractCircumstellar disks are the sites of planet formation, and the very high incidence of extrasolar planets implies that most of them actually form planetary systems. Studying the structure and evolution of protoplanetary disks can thus place important constraints on the conditions, timescales, and mechanisms associated with the planet formation process. In this review, we discuss observational results from infrared and submillimeter wavelength studies. We review disk lifetimes, transition objects, disk demographics, and highlight a few remarkable results from ALMA Early Science observations. We finish with a brief discussion of ALMA's potential to transform the field in near future.

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Planet gaps in the dust layer of 3D proto-planetary disks: Observability with ALMA

Proceedings of the International Astronomical Union ◽

10.1017/s1743921313008053 ◽

2013 ◽

Vol 8 (S299) ◽

pp. 115-116

Author(s):

J.-F. Gonzalez ◽

C. Pinte ◽

S. T. Maddison ◽

F. Ménard

Keyword(s):

Formation Process ◽

Extrasolar Planets ◽

Planet Formation ◽

Planetary Systems ◽

Dust Layer ◽

Younger Age

AbstractAmong the numerous known extrasolar planets, only a handful have been imaged directly so far, at large orbital radii and in rather evolved systems. The Atacama Large Millimeter/submillimeter Array (ALMA) will have the capacity to observe these wide planetary systems at a younger age, thus bringing a better understanding of the planet formation process. Here we explore the ability of ALMA to detect the gaps carved by planets on wide orbits.

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The Formation of Binary Stars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921307004279 ◽

2006 ◽

Vol 2 (S240) ◽

pp. 337-346

Author(s):

C.J. Clarke

Keyword(s):

Binary Stars ◽

Binary Star ◽

Vital Role ◽

Physical Processes ◽

Multiple Systems ◽

Star Forming ◽

Circumstellar Material ◽

Low Mass ◽

Body Level ◽

Hydrodynamical Simulations

AbstractI argue that binary star statistics offer the best observational constraints on current hydrodynamical simulations of star forming clusters. In these simulations, clusters form hierarchically from the bottom up, and dynamical interactions, mediated by the presence of circumstellar material, play a vital role at the lowest (few body) level of the hierarchy. Such a scenario produces a rich array of complex multiple systems whose properties are in many respects consistent with observations. I however highlight two areas of current disagreement: the simulations over-produce low mass single stars and under-produce binaries with low mass ratios. It is currently unclear to what extent these shortcomings reflect numerical issues and to what extent the omission of relevant physical processes. I conclude with a theorist's wish list for observational diagnostics that would most meaningfully constrain future modeling efforts.

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