25,967 research outputs found
The Five Planets in the Kepler-296 Binary System All Orbit the Primary: A Statistical and Analytical Analysis
Kepler-296 is a binary star system with two M-dwarf components separated by
0.2 arcsec. Five transiting planets have been confirmed to be associated with
the Kepler-296 system; given the evidence to date, however, the planets could
in principle orbit either star. This ambiguity has made it difficult to
constrain both the orbital and physical properties of the planets. Using both
statistical and analytical arguments, this paper shows that all five planets
are highly likely to orbit the primary star in this system. We performed a
Markov-Chain Monte Carlo simulation using a five transiting planet model,
leaving the stellar density and dilution with uniform priors. Using importance
sampling, we compared the model probabilities under the priors of the planets
orbiting either the brighter or the fainter component of the binary. A model
where the planets orbit the brighter component, Kepler-296A, is strongly
preferred by the data. Combined with our assertion that all five planets orbit
the same star, the two outer planets in the system, Kepler-296 Ae and
Kepler-296 Af, have radii of 1.53 +/- 0.26 and 1.80 +/- 0.31 R_earth,
respectively, and receive incident stellar fluxes of 1.40 +/- 0.23 and 0.62 +/-
0.10 times the incident flux the Earth receives from the Sun. This level of
irradiation places both planets within or close to the circumstellar habitable
zone of their parent star.Comment: Accepted for publication in Ap
VPLanet: The Virtual Planet Simulator
We describe a software package called VPLanet that simulates fundamental
aspects of planetary system evolution over Gyr timescales, with a focus on
investigating habitable worlds. In this initial release, eleven physics modules
are included that model internal, atmospheric, rotational, orbital, stellar,
and galactic processes. Many of these modules can be coupled simultaneously to
simulate the evolution of terrestrial planets, gaseous planets, and stars. The
code is validated by reproducing a selection of observations and past results.
VPLanet is written in C and designed so that the user can choose the physics
modules to apply to an individual object at runtime without recompiling, i.e.,
a single executable can simulate the diverse phenomena that are relevant to a
wide range of planetary and stellar systems. This feature is enabled by
matrices and vectors of function pointers that are dynamically allocated and
populated based on user input. The speed and modularity of VPLanet enables
large parameter sweeps and the versatility to add/remove physical phenomena to
assess their importance. VPLanet is publicly available from a repository that
contains extensive documentation, numerous examples, Python scripts for
plotting and data management, and infrastructure for community input and future
development.Comment: 75 pages, 34 figures, 10 tables, accepted to the Proceedings of the
Astronomical Society of the Pacific. Source code, documentation, and examples
available at https://github.com/VirtualPlanetaryLaboratory/vplane
The Hunt for Exomoons with Kepler (HEK): I. Description of a New Observational Project
Two decades ago, empirical evidence concerning the existence and frequency of
planets around stars, other than our own, was absent. Since this time, the
detection of extrasolar planets from Jupiter-sized to most recently Earth-sized
worlds has blossomed and we are finally able to shed light on the plurality of
Earth-like, habitable planets in the cosmos. Extrasolar moons may also be
frequent habitable worlds but their detection or even systematic pursuit
remains lacking in the current literature. Here, we present a description of
the first systematic search for extrasolar moons as part of a new observational
project called "The Hunt for Exomoons with Kepler" (HEK). The HEK project
distills the entire list of known transiting planet candidates found by Kepler
(2326 at the time of writing) down to the most promising candidates for hosting
a moon. Selected targets are fitted using a multimodal nested sampling
algorithm coupled with a planet-with-moon light curve modelling routine. By
comparing the Bayesian evidence of a planet-only model to that of a
planet-with-moon, the detection process is handled in a Bayesian framework. In
the case of null detections, upper limits derived from posteriors marginalised
over the entire prior volume will be provided to inform the frequency of large
moons around viable planetary hosts, eta-moon. After discussing our
methodologies for target selection, modelling, fitting and vetting, we provide
two example analyses.Comment: 21 pages, 8 figures, 4 tables, accepted in Ap
Detectability of Transiting Jupiters and Low-Mass Eclipsing Binaries in Sparsely Sampled Pan-STARRS-1 Survey Data
We present detailed simulations of the Pan-STARRS-1 (PS1) multi-epoch,
multi-band 3-pi Survey in order to assess its potential yield of transiting
planets and eclipsing binaries. This survey differs from dedicated transit
surveys in that it will cover the entire Northern sky but provide only sparsely
sampled light curves. Since most eclipses would be detected at only a single
epoch, the 3-pi Survey will be most sensitive to deep eclipses (> 0.10 mag)
caused by Jupiters transiting M dwarfs and eclipsing stellar/substellar
binaries. The survey will also provide parallaxes for the ~400,000 stars within
100 pc which will enable a volume-limited eclipse search, reducing the number
of astrophysical false positives compared to previous magnitude-limited
searches. Using the best available empirical data, we constructed a model of
the extended solar neighborhood that includes stars, brown dwarfs, and a
realistic binary population. We computed the yield of deeply eclipsing systems
using both a semi-analytic and a full Monte Carlo approach. We examined
statistical tests for detecting single-epoch eclipses in sparsely sampled data
and assessed their vulnerability to false positives due to stellar variability.
Assuming a short-period planet frequency of 0.5% for M dwarfs, our simulations
predict that about a dozen transiting Jupiters around low-mass stars (M < 0.3
Msun) within 100 pc are potentially detectable in the PS1 3-pi Survey, along
with ~300 low-mass eclipsing binaries (both component masses < 0.5 Msun),
including ~10 eclipsing field brown dwarfs. Extensive follow-up observations
would be required to characterize these candidate eclipsing systems, thereby
enabling comprehensive tests of structural models and novel insights into the
planetary architecture of low-mass stars.Comment: ApJ, in pres
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