arXiv subjects

John E. Chambers

Publications and source records attributed to John E. Chambers.

23 records · Page 2Linked to original sources

arXiv2008

Low Mass Companions for Five Solar-Type Stars from the Magellan Planet Search Program

We report low mass companions orbiting five Solar-type stars that have emerged from the Magellan precision Doppler velocity survey, with minimum (Msini) masses ranging from 1.2 to 25 Mjup. These nearby target stars range from mildly metal-poor to metal-rich, and appear to have low chromospheric activity. The companions to the brightest two of these stars have previously been reported from the CORALIE survey. Four of these companions (HD 48265-b, HD 143361-b, HD 28185-b, HD 111232-b) are low-mass Jupiter-like planets in eccentric intermediate and long-period orbits. On the other hand, the companion to HD 43848 appears to be a long period brown dwarf in a very eccentric orbit.

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arXiv2007

N-body integrators for planets in binary star systems

Symplectic integrators are the tool of choice for many researchers studying dynamical systems because of their good long-term energy conservation properties. For systems with a dominant central mass, symplectic integrators are also highly efficient. In this chapter, I describe the theory of symplectic integrators in terms of Lie series. I show how conventional symplectic algorithms have been adapted for use in binary-star systems to study problems such as the dynamical stability of multi-planet systems and the accretion of planets from planetesimals. This is achieved by devising new coordinate systems for the wide-binary and close-binary cases separately. I show how the performance of these algorithms can be improved at little extra cost using symplectic correctors. Finally, I discuss drawbacks of these algorithms, in particular in dealing with close encounters with one or both members of the binary, and the prospects for overcoming these problems.

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arXiv2007

The instability of planetary systems in binaries: how the Kozai mechanism leads to strong planet-planet interactions

In this letter we consider the evolution of a planetary system around a star inside a wide binary. We simulate numerically the evolution of the planetary orbits for both co-planar and highly-inclined systems. We find that the Kozai mechanism operates in the latter case. This produces a highly eccentric outer planet whose orbit crosses those of some of the inner planets. Strong planet-planet interactions then follow resulting in the ejection of one or more planets. We note that planetary systems resembling our solar system, formed around single stars in stellar clusters may exchange into binaries and thus will be vulnerable to planet stripping. This process will reduce the number of solar-system like planetary systems, and may produce at least some of the observed extra-solar planets.

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arXiv2007

Terrestrial Planet Formation Around Individual Stars Within Binary Star Systems

We calculate herein the late stages of terrestrial planet accumulation around a solar type star that has a binary companion with semimajor axis larger than the terrestrial planet region. We perform more than one hundred simulations to survey binary parameter space and to account for sensitive dependence on initial conditions in these dynamical systems. As expected, sufficiently wide binaries leave the planet formation process largely unaffected. As a rough approximation, binary stars with periastron $q_B > 10$ AU have minimal effect on terrestrial planet formation within $\sim 2$ AU of the primary, whereas binary stars with $q_B \la$ 5 AU restrict terrestrial planet formation to within $\sim$ 1 AU of the primary star. Given the observed distribution of binary orbital elements for solar type primaries, we estimate that about 40 -- 50 percent of the binary population is wide enough to allow terrestrial planet formation to take place unimpeded. The large number of simulations allows for us to determine the distribution of results -- the distribution of plausible terrestrial planet systems -- for effectively equivalent starting conditions. We present (rough) distributions for the number of planets, their masses, and their orbital elements.

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arXiv2001

Short-Term Dynamical Interactions Among Extrasolar Planets

We show that short-term perturbations among massive planets in multiple planet systems can result in radial velocity variations of the central star which differ substantially from velocity variations derived assuming the planets are executing independent Keplerian motions. We discuss two alternate fitting methods which can lead to an improved dynamical description of multiple planet systems. In the first method, the osculating orbital elements are determined via a Levenberg-Marquardt minimization scheme driving an N-body integrator. The second method is an improved analytic model in which orbital elements are allowed to vary according to a simple model for resonant interactions between the planets. Both of these methods can determine the true masses for the planets by eliminating the sin(i) degeneracy inherent in fits that assume independent Keplerian motions. We apply our fitting methods to the GJ876 radial velocity data (Marcy et al. 2001), and argue that the mass factors for the two planets are likely in the 1.25-2.0 range

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