6 research outputs found
Signs of Similar Stellar Obliquity Distributions for Hot and Warm Jupiters Orbiting Cool Stars
Transiting giant planets provide a natural opportunity to examine stellar
obliquities, which offer clues about the origin and dynamical histories of
close-in planets. Hot Jupiters orbiting Sun-like stars show a tendency for
obliquity alignment, which suggests that obliquities are rarely excited or that
tidal realignment is common. However, the stellar obliquity distribution is
less clear for giant planets at wider separations where realignment mechanisms
are not expected to operate. In this work, we uniformly derive line-of-sight
inclinations for 47 cool stars ( 6200 K) harboring
transiting hot and warm giant planets by combining rotation periods, stellar
radii, and measurements. Among the systems that show signs of
spin-orbit misalignment in our sample, three are identified as being misaligned
here for the first time. Of particular interest are Kepler-1654, one of the
longest-period (1047 d; 2.0 AU) giant planets in a misaligned system, and
Kepler-30, a multi-planet misaligned system. By comparing the reconstructed
underlying inclination distributions, we find that the inferred minimum
misalignment distributions of hot Jupiters spanning = 3-20 (
0.01-0.1 AU) and warm Jupiters spanning = 20-400 ( 0.1-1.9
AU) are in good agreement. With 90 confidence, at least 24 of
warm Jupiters and 14 of hot Jupiters around cool stars are
misaligned by at least 10. Most stars harboring warm Jupiters are
therefore consistent with spin-orbit alignment. The similarity of hot and warm
Jupiter misalignment rates suggests that either the occasional misalignments
are primordial and originate in misaligned disks, or the same underlying
processes that create misaligned hot Jupiters also lead to misaligned warm
Jupiters.Comment: AJ, accepte
The Impact of Bayesian Hyperpriors on the Population-Level Eccentricity Distribution of Imaged Planets
Orbital eccentricities directly trace the formation mechanisms and dynamical
histories of substellar companions. Here, we study the effect of hyperpriors on
the population-level eccentricity distributions inferred for the sample of
directly imaged substellar companions (brown dwarfs and cold Jupiters) from
hierarchical Bayesian modeling (HBM). We find that the choice of hyperprior can
have a significant impact on the population-level eccentricity distribution
inferred for imaged companions, an effect that becomes more important as the
sample size and orbital coverage decrease to values that mirror the existing
sample. We reanalyse the current observational sample of imaged giant planets
in the 5-100 AU range from Bowler et al. (2020) and find that the underlying
eccentricity distribution implied by the imaged planet sample is broadly
consistent with the eccentricity distribution for close-in exoplanets detected
using radial velocities. Furthermore, our analysis supports the conclusion from
that study that long-period giant planets and brown dwarf eccentricity
distributions differ by showing that it is robust to the choice of hyperprior.
We release our HBM and forward modeling code in an open-source Python package,
ePop!, and make it freely available to the community.Comment: 18 pages, 11 figures. Accepted for publication in The Astronomical
Journa
orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
orbitize! is an open-source, object-oriented software package for fitting the orbits of directly imaged objects. It packages the Orbits for the Impatient (OFTI) algorithm and a parallel-tempered Markov Chain Monte Carlo (MCMC) algorithm into a consistent and intuitive Python API. orbitize! makes it easy to run standard astrometric orbit fits; in less than 10 lines of code, users can read in data, perform one fit using OFTI and another using MCMC, and make two publication-ready figures. Extensive pedagogical tutorials, intended to be navigable by both orbit-fitting novices and seasoned experts, are available on our documentation page. We have designed the orbitize! API to be flexible and easy to use/modify for unique cases. orbitize! was designed by members of the exoplanet imaging community to be a central repository for algorithms, techniques, and know-how developed by this community. We intend for it to continue to expand and change as the field progresses and new techniques are developed, and call for community involvement in this process. Complete and up-to-date documentation is available at orbitize.info, and the source code is available at github.com/sblunt/orbitize
Rotation Periods, Inclinations, and Obliquities of Cool Stars Hosting Directly Imaged Substellar Companions: Spin-Orbit Misalignments are Common
The orientation between a star's spin axis and a planet's orbital plane
provides valuable information about the system's formation and dynamical
history. For non-transiting planets at wide separations, true stellar
obliquities are challenging to measure, but lower limits on spin-orbit
orientations can be determined from the difference between the inclination of
the star's rotational axis and the companion's orbital plane (). We
present results of a uniform analysis of rotation periods, stellar
inclinations, and obliquities of cool stars (SpT F5) hosting directly
imaged planets and brown dwarf companions. As part of this effort, we have
acquired new values for 22 host stars with the high-resolution
Tull spectrograph at the Harlan J. Smith telescope. Altogether our sample
contains 62 host stars with rotation periods, most of which are newly measured
using light curves from the Transiting Exoplanet Survey Satellite. Among these,
53 stars have inclinations determined from projected rotational and equatorial
velocities, and 21 stars predominantly hosting brown dwarfs have constraints on
. Eleven of these (52% of the sample) are likely
misaligned, while the remaining ten host stars are consistent with spin-orbit
alignment. As an ensemble, the minimum obliquity distribution between 10-250 AU
is more consistent with a mixture of isotropic and aligned systems than either
extreme scenario alone--pointing to direct cloud collapse, formation within
disks bearing primordial alignments and misalignments, or architectures
processed by dynamical evolution. This contrasts with stars hosting directly
imaged planets, which show a preference for low obliquities. These results
reinforce an emerging distinction between the orbits of long-period brown
dwarfs and giant planets in terms of their stellar obliquities and orbital
eccentricities.Comment: AJ, accepte
Improved Constraints on the 21 cm EoR Power Spectrum and the X-Ray Heating of the IGM with HERA Phase I Observations
We report the most sensitive upper limits to date on the 21 cm epoch of
reionization power spectrum using 94 nights of observing with Phase I of the
Hydrogen Epoch of Reionization Array (HERA). Using similar analysis techniques
as in previously reported limits (HERA Collaboration 2022a), we find at 95%
confidence that Mpc) mK at and that Mpc mK at , an improvement by a factor of 2.1 and 2.6 respectively. These limits are
mostly consistent with thermal noise over a wide range of after our data
quality cuts, despite performing a relatively conservative analysis designed to
minimize signal loss. Our results are validated with both statistical tests on
the data and end-to-end pipeline simulations. We also report updated
constraints on the astrophysics of reionization and the cosmic dawn. Using
multiple independent modeling and inference techniques previously employed by
HERA Collaboration (2022b), we find that the intergalactic medium must have
been heated above the adiabatic cooling limit at least as early as ,
ruling out a broad set of so-called "cold reionization" scenarios. If this
heating is due to high-mass X-ray binaries during the cosmic dawn, as is
generally believed, our result's 99% credible interval excludes the local
relationship between soft X-ray luminosity and star formation and thus requires
heating driven by evolved low-metallicity stars.Comment: 57 pages, 37 figures. Updated to match the accepted ApJ version.
Corresponding author: Joshua S. Dillo
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orbitize!: A Comprehensive Orbit-fitting Software Package for the High-contrast Imaging Community
orbitize! is an open-source, object-oriented software package for fitting the orbits of directly imaged objects. It packages the Orbits for the Impatient (OFTI) algorithm and a parallel-tempered Markov Chain Monte Carlo (MCMC) algorithm into a consistent and intuitive Python API. orbitize! makes it easy to run standard astrometric orbit fits; in less than 10 lines of code, users can read in data, perform one fit using OFTI and another using MCMC, and make two publication-ready figures. Extensive pedagogical tutorials, intended to be navigable by both orbit-fitting novices and seasoned experts, are available on our documentation page. We have designed the orbitize! API to be flexible and easy to use/modify for unique cases. orbitize! was designed by members of the exoplanet imaging community to be a central repository for algorithms, techniques, and know-how developed by this community. We intend for it to continue to expand and change as the field progresses and new techniques are developed, and call for community involvement in this process. Complete and up-to-date documentation is available at.orbitize.info, and the source code is available at.github.com/sblunt/orbitize.This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]