152 research outputs found
Detectability of Earth-like Planets in Circumstellar Habitable Zones of Binary Star Systems with Sun-like Components
Given the considerable percentage of stars that are members of binaries or
stellar multiples in the Solar neighborhood, it is expected that many of these
binaries host planets, possibly even habitable ones. The discovery of a
terrestrial planet in the alpha Centauri system supports this notion. Due to
the potentially strong gravitational interaction that an Earth-like planet may
experience in such systems, classical approaches to determining habitable
zones, especially in close S-Type binary systems, can be rather inaccurate.
Recent progress in this field, however, allows to identify regions around the
star permitting permanent habitability. While the discovery of alpha Cen Bb has
shown that terrestrial planets can be detected in solar-type binary stars using
current observational facilities, it remains to be shown whether this is also
the case for Earth analogues in habitable zones. We provide analytical
expressions for the maximum and RMS values of radial velocity and astrometric
signals, as well as transit probabilities of terrestrial planets in such
systems, showing that the dynamical interaction of the second star with the
planet may indeed facilitate the planets detection. As an example, we discuss
the detectability of additional Earth-like planets in the averaged, extended,
and permanent habitable zones around both stars of the alpha Centauri system.Comment: accepted for publication in The Astrophysical Journa
Impact flux of asteroids and water transport to the habitable zone in binary star systems
By now, observations of exoplanets have found more than 50 binary star
systems hosting 71 planets. We expect these numbers to increase as more than
70% of the main sequence stars in the solar neighborhood are members of binary
or multiple systems. The planetary motion in such systems depends strongly on
both the parameters of the stellar system (stellar separation and eccentricity)
and the architecture of the planetary system (number of planets and their
orbital behaviour). In case a terrestrial planet moves in the so-called
habitable zone (HZ) of its host star, the habitability of this planet depends
on many parameters. A crucial factor is certainly the amount of water. We
investigate in this work the transport of water from beyond the snow-line to
the HZ in a binary star system and compare it to a single star system
Dynamics of passing-stars-perturbed binary star systems
In this work, we investigate the dynamical effects of a sequence of close
encounters over 200 Myr varying in the interval of 10000 -- 100000 au between a
binary star system and passing stars with masses ranging from 0.1 to
10. We focus on binaries consisting of two Sun-like stars with
various orbital separations from 50 au to 200 au
initially on circular-planar orbits. We treat the problem statistically since
each sequence is cloned 1000 times. Our study shows that orbits of binaries
initially at = 50 au will slightly be perturbed by
each close encounter and exhibit a small deviation in eccentricity (+0.03) and
in periapsis distance (+1 and -2 au) around the mean value. However increasing
will drastically increase these variances: up to
+0.45 in eccentricity and between +63 au and -106 au in periapsis, leading to a
higher rate of disrupted binaries up to 50% after the sequence of close
encounters. Even though the secondary star can remain bound to the primary,
20% of the final orbits will have inclinations greater than 10.
As planetary formation already takes place when stars are still members of
their birth cluster, we show that the variances in eccentricity and periapsis
distance of Jupiter- and Saturn-like planets will inversely decrease with
after successive fly-bys. This leads to higher
ejection rate at = 50 au but to a higher extent for
Saturn-likes (60%) as those planets' apoapsis distances cross the critical
stability distance for such binary separation.Comment: Accepted for publication (MNRAS
Disc-protoplanet interaction Influence of circumprimary radiative discs on self-gravitating protoplanetary bodies in binary star systems
Context. More than 60 planets have been discovered so far in systems that
harbour two stars, some of which have binary semi-major axes as small as 20 au.
It is well known that the formation of planets in such systems is strongly
influenced by the stellar components, since the protoplanetary disc and the
particles within are exposed to the gravitational influence of the binary.
However, the question on how self-gravitating protoplanetary bodies affect the
evolution of a radiative, circumprimary disc is still open. Aims. We present
our 2D hydrodynamical GPU-CPU code and study the interaction of several
thousands of self-gravitating particles with a viscous and radiative
circumprimary disc within a binary star system. To our knowledge this program
is the only one at the moment that is capable to handle this many particles and
to calculate their influence on each other and on the disc. Methods. We
performed hydrodynamical simulations of a circumstellar disc assuming the
binary system to be coplanar. Our gridbased staggered mesh code relies on ideas
from ZEUS-2D, where we implemented the FARGO algorithm and an additional energy
equation for the radiative cooling according to opacity tables. To treat
particle motion we used a parallelised version of the precise Bulirsch - Stoer
algorithm. Four models in total where computed taking into account (i) only
N-body interaction, (ii) N-body and disc interaction, (iii) the influence of
computational parameters (especially smoothing) on N-body interaction, and (iv)
the influence of a quiet low-eccentricity disc while running model (ii). The
impact velocities where measured at two different time intervals and were
compared. Results. We show that the combination of disc- and N-body
self-gravity can have a significant influence on the orbit evolution of roughly
Moon sized protoplanets
An Analytic Method to determine Habitable Zones for S-Type Planetary Orbits in Binary Star Systems
With more and more extrasolar planets discovered in and around binary star
systems, questions concerning the determination of the classical Habitable Zone
arise. Do the radiative and gravitational perturbations of the second star
influence the extent of the Habitable Zone significantly, or is it sufficient
to consider the host-star only? In this article we investigate the implications
of stellar companions with different spectral types on the insolation a
terrestrial planet receives orbiting a Sun-like primary. We present time
independent analytical estimates and compare these to insolation statistics
gained via high precision numerical orbit calculations. Results suggest a
strong dependence of permanent habitability on the binary's eccentricity, as
well as a possible extension of Habitable Zones towards the secondary in close
binary systems.Comment: submitted to ApJ, status: accepte
Circumstellar Habitable Zones of Binary Star Systems in the Solar Neighborhood
Binary and multiple systems constitute more than half of the total stellar
population in the Solar neighborhood (Kiseleva-Eggleton and Eggleton 2001).
Their frequent occurrence as well as the fact that more than 70 (Schneider et
al. 2011) planets have already been discovered in such configurations - most
noteably the telluric companion of alpha Centauri B (Dumusque et al. 2012) -
make them interesting targets in the search for habitable worlds. Recent
studies (Eggl et al. 2012b, Forgan 2012) have shown, that despite the
variations in gravitational and radiative environment, there are indeed
circumstellar regions where planets can stay within habitable insolation limits
on secular dynamical timescales. In this article we provide habitable zones for
19 near S-Type binary systems from the Hipparchos and WDS catalogues with
semimajor axes between 1 and 100 AU. Hereby, we accounted for the combined
dynamical and radiative influence of the second star on the Earth-like planet.
Out of the 19 systems presented, 17 offer dynamically stable habitable zones
around at least one component. The 17 potentially habitable systems contain 5
F, 3 G, 7 K and 16 M class stars. As their proximity to the Solar System (d <
31 pc) makes the selected binary stars exquisite targets for observational
campaigns, we offer estimates on radial velocity, astrometric and transit
signatures produced by habitable Earth-like planets in eccentric circumstellar
orbits
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