Planets in Evolved Binary Systems

Cornell University - arXiv, 2010

Planets are typically thought to form in protoplanetary disks left over from protostellar disk of their newly formed host star. However, an additional planetary formation route may exist in old evolved binary systems. In such systems stellar evolution could lead to the formation of symbiotic stars, where mass transferred from the expanding evolved star to its binary companion could form an accretion disk around it. Such a disk could provide the necessary environment for the formation of a second generation of planets in both circumstellar or circumbinary configurations. Pre-existing first generation planets surviving the post-MS evolution of such systems may serve as seeds for, and/or interact with, the second generation planets, possibly forming atypical planetary systems. Second generation planetary systems should be typically found in white dwarf binary systems, and may show various observational signatures. Most notably, second generation planets could form in environment which are inaccessible, or less favorable, for first generation planets. The orbital phase space available for the second generation planets could be forbidden (in terms of the system stability) to first generation planets in the pre-evolved progenitor binaries. In addition planets could form in metal poor environments such as globular clusters and/or in double compact object binaries. Observations of planets in such forbidden or unfavorable regions may serve to uniquely identify their second generation character. Finally, we point out a few observed candidate second generation planetary systems, including PSR B1620-26 (in a globular cluster), Gl 86, HD 27442 and all of the currently observed circumbinary planet candidates. A second generation origin for these systems could naturally explain their unique configurations.

Astrobiology, 2010

Alibert, Y.; Broeg, C.; Benz, W.; Wuchterl, G.; Grasset, O.; Sotin, C.

Astrophysics and Space Science Library, 2010

2013

Aims. We explore the relations between physical and orbital properties of planets and properties of their host stars to identify the main observable signatures of the formation and evolution processes of planetary systems. Methods. We used a large sample of FGK dwarf planet-hosting stars with stellar parameters derived in a homogeneous way from the SWEET-Cat database to study the relation between stellar metallicity and position of planets in the period-mass diagram. We then used all the radial-velocity-detected planets orbiting FGK stars to explore the role of planet-disk and planet-planet interaction on the evolution of orbital properties of planets with masses above 1M Jup. Results. Using a large sample of FGK dwarf hosts we show that planets orbiting metal-poor stars have longer periods than those in metal-rich systems. This trend is valid for masses at least from ≈10M ⊕ to ≈4M Jup. Earth-like planets orbiting metal-rich stars always show shorter periods (fewer than 20 days) than those orbiting metal-poor stars. However, in the short-period regime there are a similar number of planets orbiting metal-poor stars. We also found statistically significant evidence that very high mass giants (with a mass higher than 4M Jup) have on average more eccentric orbits than giant planets with lower mass. Finally, we show that the eccentricity of planets with masses higher than 4M Jup tends to be lower for planets with shorter periods. Conclusions. Our results suggest that the planets in the P-M P diagram are evolving differently because of a mechanism that operates over a wide range of planetary masses. This mechanism is stronger or weaker depending on the metallicity of the respective system. One possibility is that planets in metal-poor disks form farther out from their central star and/or they form later and do not have time to migrate as far as the planets in metal-rich systems. The trends and dependencies obtained for very high mass planetary systems suggest that planet-disk interaction is a very important and orbit-shaping mechanism for planets in the high-mass domain.

Space Science Reviews, 2016

The growing body of observational data on extrasolar planets and protoplanetary disks has stimulated intense research on planet formation and evolution in the past few years. The extremely diverse, sometimes unexpected physical and orbital characteristics of exoplanets lead to frequent updates on the mainstream scenarios for planet formation and evolution, but also to the exploration of alternative avenues. The aim of this review is to bring together classical pictures and new ideas on the formation, orbital and internal evolutions of planets, highlighting the key role of the protoplanetary disk in the various parts of the theory. We begin by briefly reviewing the conventional mechanism of core accretion by the growth of planetesimals, and discuss a relatively recent model of core growth through the accretion of pebbles. We review the basic physics of planet-disk interactions, recent progress in this area, and discuss their role in observed planetary systems. We address the most important effects of planets internal evolution, like cooling and contraction, the mass-luminosity relation, and the bulk composition expressed in the mass-radius and mass-mean density relations. Keywords planets and satellites: formation • planets and satellites: interiors • protoplanetary disks • planet-disk interactions 1 Introduction Planet formation and evolution is a fast-moving field, stimulated by the rapid increase in the number of exoplanets and their great diversity. Despite the wealth of observational data on planetary systems, including our own, it is difficult to have a general theory for planet formation and evolution as it involves a broad range of physical processes that happen at

Arxiv preprint arXiv: …, 2009

Abstract: Newly-formed planetary systems with ages of< 10 Myr offer many unique insights into the formation, evolution, and fundamental properties of extrasolar planets. These planets have fallen beyond the limits of past surveys, but as we enter the next decade, we ...

The Astrophysical Journal, 2005

We report Doppler measurements for six nearby G-and K-type main-sequence stars that show multiple low-mass companions, at least one of which has planetary mass. One system has three planets, the fourth triple-planet system known around a normal star, and another has an extremely low minimum mass of 18 M È . HD 128311 ( K0 V ) has two planets (one previously known) with minimum masses (M sin i) of 2.18M J and 3.21M J and orbital periods of 1.26 and 2.54 yr, suggesting a possible 2:1 resonance. For HD 108874 (G5 V ), the velocities reveal two planets (one previously known) having minimum masses and periods of (M sin i b ¼ 1:36M J , P b ¼ 1:08 yr) and (M sin i c ¼ 1:02M J , P c ¼ 4:4 yr). HD 50499 (G1 V ) has a planet with P ¼ 6:8 yr and M sin i ¼ 1:7M J , and the velocity residuals exhibit a trend of À4.8 m s À1 yr À1 , indicating a more distant companion with P > 10 yr and minimum mass of 2M J . HD 37124 (G4 IV-V ) has three planets, one having M sin i ¼ 0:61M J and P ¼ 154:5 days, as previously known. We find two plausible triple-planet models that fit the data, both having a second planet near P ¼ 840 days, with the more likely model having its third planet in a 6 yr orbit and the other one in a 29 day orbit. For HD 190360, we confirm the planet having P ¼ 7:9 yr and M sin i ¼ 1:5M J as found by the Geneva team, but we find a distinctly noncircular orbit with e ¼ 0:36 AE 0:03, rendering this not an analog of Jupiter as had been reported. Our velocities also reveal a second planet with P ¼ 17:1 days and M sin i ¼ 18:1 M È . HD 217107 (G8 IV) has a previously known ''hot Jupiter'' with M sin i ¼ 1:4M J and P ¼ 7:13 days, and we confirm its high eccentricity, e ¼ 0:13. The velocity residuals reveal an outer companion in an eccentric orbit, having minimum mass of M sin i > 2M J , eccentricity e $ 0:5, and a period P > 8 yr, implying a semimajor axis a > 4 AU and providing an opportunity for direct detection. We have obtained high-precision photometry of five of the six planetary host stars with three of the automated telescopes at Fairborn Observatory. We can rule out significant brightness variations in phase with the radial velocities in most cases, thus supporting planetary reflex motion as the cause of the velocity variations. Transits are ruled out to very shallow limits for HD 217107 and are also shown to be unlikely for the prospective inner planets of the HD 37124 and HD 108874 systems. HD 128311 is photometrically variable with an amplitude of 0.03 mag and a period of 11.53 days, which is much shorter than the orbital periods of its two planetary companions. This rotation period explains the origin of periodic velocity residuals to the two-planet model of this star. All of the planetary systems here would be further constrained with astrometry by the Space Interferometry Mission.

2004

We propose to trace the evolution of planetary systems at all ages ranging from: (1) 3-10 Myr when stellar accretion from the disk terminates; to (2) 10-100 Myr when planets achieve their final masses via coalescence of solids and accretion of remnant molecular gas; to (3) 100-1000 Myr when the final architecture of solar systems takes form and frequent collisions

International Astronomical Union Colloquium

Orbital properties of extra-solar planets are briefly recalled and compared with equivalent features of stellar binaries. Similarities and differences are discussed. Among the more than 115 extra-solar planets discovered to date, 19 are orbiting a component of a binary system. We discuss the properties of this subsample and compare them with the equivalent characteristics of planets around single stars. Differences in the mass-period-eccentricity distributions are observed: exoplanets with m2 sin i > 2 MJup and P≤ 40-100 days are in binaries and present low eccentricities. In the context of the migration scenario, these characteristics are tentatively explained in the light of recent simulations of planet-disk interactions showing an increased accretion and migration rates of planets in case an additional perturbing close stellar companion is present in the system. Finally, different observational approaches to find planets in long-period spectroscopic binaries aiming to improve ...

Journal of Physics: Conference Series, 2016

Searching for planetary companions to evolved stars (e.g., white dwarfs (WD) and Cataclysmic Variables (CV)) can provide insight into the interaction between planets and evolved stars as well as on the ultimate fate of planets. We have monitored decades of CVs and their progenitors including some detached WD binaries since 2006 to search for planets orbiting these systems. In the present paper, we will show some observational results of circumbinary planets in orbits around CVs and their progenitors. Some of our findings include planets with the shortest distance to the central evolved binaries and a few multiple planetary systems orbiting binary stars. Finally, by comparing the observational properties of planetary companions to single WDs and WD binaries, the interaction between planets and evolved stars and the ultimate fate of planets are discussed.