* Astronomy

Members Login
Username 
 
Password 
    Remember Me  
Post Info TOPIC: Wide binary systems


L

Posts: 131433
Date:
RE: Wide binary systems
Permalink  
 


Title: Planetary system disruption by Galactic perturbations to wide binary stars
Authors: Nathan A. Kaib, Sean N. Raymond, Martin Duncan,

Because they are so weakly bound, the orbits of wide binary stars evolve greatly under the influence of the Galactic tide and impulses from passing field stars. Most systems eventually pass through phases of high eccentricity, and this can have catastrophic consequences for the planets orbiting within these binary systems. During these eccentric phases, close encounters between the two binary members occur, and any planets orbiting the stars can be strongly perturbed. We use numerical simulations to study the planetary dynamics within such wide binaries, and we find that dynamical instabilities are common. For planetary configurations like our own solar system, we find that a wide binary companion (a > 1000 AU) will trigger planetary ejections in 1/3 to 1/2 of all systems. Interestingly, these ejections and instabilities typically occur only after hundreds of Myrs or Gyrs of evolution, possibly generating events similar to the LHB instability that occurred in our own solar system.

Read more

 

Wide binary stars study

Two simulations of planetary system disruption by galactic disturbances to wide binary stars. On the left is a zoomed-out view showing the orbit of a hypothetical 0.1 solar mass binary star around our own solar system with an initial orbital separation of 10,000 AU (1 AU is the distance between the Earth and the Sun). On the right is a zoomed-in view of the orbits of Jupiter, Saturn, Uranus, and Neptune. As the binary orbit becomes eccentric, this eventually excites the planetary orbits and Uranus and Neptune are both ejected.
See more



__________________


L

Posts: 131433
Date:
Wide Binary Stars
Permalink  
 


Title: The Evolution of Wide Binary Stars
Authors: Yan-Fei Jiang, Scott Tremaine

We study the orbital evolution of wide binary stars in the solar neighbourhood due to gravitational perturbations from passing stars. We include the effects of the Galactic tidal field and continue to follow the stars after they become unbound. For a wide variety of initial semi-major axes and formation times, we find that the number density (stars per unit logarithmic interval in projected separation) exhibits a minimum at a few times the Jacobi radius r_J, which equals 1.7 pc for a binary of solar-mass stars. The density peak interior to this minimum arises from the primordial distribution of bound binaries, and the exterior density, which peaks at ~  100--300 pc separation, arises from formerly bound binaries that are slowly drifting apart. The exterior peak gives rise to a significant long-range correlation in the positions and velocities of disk stars that should be detectable in large astrometric surveys such as GAIA that can measure accurate three-dimensional distances and velocities.

Read more (3702kb, PDF)

__________________


L

Posts: 131433
Date:
Wide binary systems
Permalink  
 


Title: New Distant Companions to Known Nearby Stars. II. Faint companions of Hipparcos stars and the frequency of wide binary systems
Authors: Sébastien Lépine, Bethany Bongiorno

We perform a search for faint, common proper motion companions of Hipparcos stars using the recently published LSPM-north catalogue of stars with proper motion mu>0.15 arcsec/yr. Our survey uncovers a total of 521 systems with angular separations 3" < Delta theta < 1500", with 15 triples and 1 quadruple. Our new list of wide systems with Hipparcos primaries includes 130 systems identified here for the first time, including 44 in which the secondary star has V>15.0. Our census is statistically complete for secondaries with angular separations 20" < Delta theta < 300" and apparent magnitudes V<19.0. Overall, we find that at least 9.5 % of nearby (d<100 pc) Hipparcos stars have distant stellar companions with projected orbital separations s > 1,000 AU. We observe that the distribution in orbital separations is consistent with Opik's law f(s) ds ~ s^-1 ds only up to separation s~4,000 AU, beyond which it follows a more steeply decreasing power law f(s) ds ~ s^-l ds with l=1.6±0.1. We also find that the luminosity function of the secondaries is significantly different from that of the single stars field population, showing a relative deficiency in low-luminosity (8<M_V<14) objects. The observed trends suggest either a formation mechanism biased against low-mass companions, or a disruption over time of systems with low gravitational binding energy.

Read more (249kb, PDF)

__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard