2,193 research outputs found
Orbital Parameter Determination for Wide Stellar Binary Systems in the Age of Gaia
The orbits of binary stars and planets, particularly eccentricities and
inclinations, encode the angular momentum within these systems. Within stellar
multiple systems, the magnitude and (mis)alignment of angular momentum vectors
among stars, disks, and planets probes the complex dynamical processes guiding
their formation and evolution. The accuracy of the \textit{Gaia} catalog can be
exploited to enable comparison of binary orbits with known planet or disk
inclinations without costly long-term astrometric campaigns. We show that
\textit{Gaia} astrometry can place meaningful limits on orbital elements in
cases with reliable astrometry, and discuss metrics for assessing the
reliability of \textit{Gaia} DR2 solutions for orbit fitting. We demonstrate
our method by determining orbital elements for three systems (DS Tuc AB, GK/GI
Tau, and Kepler-25/KOI-1803) using \textit{Gaia} astrometry alone. We show that
DS Tuc AB's orbit is nearly aligned with the orbit of DS Tuc Ab, GK/GI Tau's
orbit might be misaligned with their respective protoplanetary disks, and the
Kepler-25/KOI-1803 orbit is not aligned with either component's transiting
planetary system. We also demonstrate cases where \textit{Gaia} astrometry
alone fails to provide useful constraints on orbital elements. To enable
broader application of this technique, we introduce the python tool
\texttt{lofti\_gaiaDR2} to allow users to easily determine orbital element
posteriors.Comment: 18 pages, 10 figures, accepted for publication in Ap
Larval culture of the calico scallop, Argopecten gibbus
Mature calico scallops, Argopecten gibbus, collected from the grounds off Cape Kennedy, Florida, were induced to spawn in the laboratory. Fertilized eggs were reared to postlarvae in sea water of 23° C ± 2.0° C at a salinity of 35 %o. The external morphology of eggs and developing larval stages are described
The Impact of Stellar Multiplicity on Planetary Systems, I.:The Ruinous Influence of Close Binary Companions
The dynamical influence of binary companions is expected to profoundly influence planetary systems. However, the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain; despite numerous theoretical hurdles to their formation and survival, at least some binary systems clearly host planets. We present high-resolution imaging of 382 Kepler Objects of Interest (KOIs) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry on the Keck II telescope. Among the full sample of 506 candidate binary companions to KOIs, we super-resolve some binary systems to projected separations of 0.4; we instead only found 23 companions (a 4.6σ deficit), many of which must be wider pairs that are only close in projection. When the binary population is parametrized with a semimajor axis cutoff a cut and a suppression factor inside that cutoff S bin, we find with correlated uncertainties that inside au, the planet occurrence rate in binary systems is only times that of wider binaries or single stars. Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion
Low temperature transition to a superconducting phase in boron-doped silicon films grown on (001)-oriented silicon wafers
We report on a detailed analysis of the superconducting properties of
boron-doped silicon films grown along the 001 direction by Gas Immersion Laser
Doping. The doping concentration cB has been varied up to approx. 10 at.% by
increasing the number of laser shots to 500. No superconductivity could be
observed down to 40mK for doping level below 2.5 at.%. The critical temperature
Tc then increased steeply to reach 0.6K for cB = 8 at%. No hysteresis was found
for the transitions in magnetic field, which is characteristic of a type II
superconductor. The corresponding upper critical field Hc2(0) was on the order
of 1000 G, much smaller than the value previously reported by Bustarret et al.
in Nature (London) 444, 465 (2006).Comment: 4 pages including 4 figures, submitted to PRB-Rapid Communicatio
DISCOVERY OF A LOW-LUMINOSITY, TIGHT SUBSTELLAR BINARY AT THE T/Y TRANSITION
We have discovered that the brown dwarf WISEJ014656.66+423410.0 is a close
binary (0.08750.0021 arcsec, 0.93 AU) from Keck laser
guide star adaptive optics imaging. Our photometry for this system reveals that
both components are less luminous than those in any known substellar binary.
Combining a new integrated-light spectrum (T9p) and resolved YJH-band
photometry from Keck allows us to perform spectral decomposition and assign
component types of T9 and Y0. Many of the unusual features in the spectrum
might be explained by high surface gravity: Y-band peak broadened to the blue;
J-band peak broadened to the red; H-band peak shifted slightly to the red; and
red Y-J colors. Interestingly, the very low component luminosities imply that
the T9 primary is unexpectedly cold ( = 34545 K assuming an
age of 10 Gyr), making it 100 K cooler than any other late-T dwarf and
comparable to Y dwarfs. One intriguing explanation for this apparent
discrepancy is that the J- and H-band spectral features that trigger the
transition from T to Y spectral types are highly gravity-dependent. This can be
tested directly in the very near future by orbit monitoring. We constrain the
orbital period to be 10 yr by combining evolutionary model-based mass
estimates for the components (1221 , 1 at 10
Gyr) with a statistical constraint on the semimajor axis (1.3 AU).
Such a period is shorter than any other known T/Y transition binary, meaning
that WISEJ0146+4234AB will likely yield a dynamical mass within the next few
years.Comment: Accepted to ApJ (2015 Feb 14); 24 pages, 4 figures, 5 table
ADAPTIVE OPTICS IMAGING OF VHS 1256-1257: A LOW MASS COMPANION TO A BROWN DWARF BINARY SYSTEM
Recently, Gauza et al. (2015) reported the discovery of a companion to the
late M-dwarf, VHS J125601.92-125723.9 (VHS 1256-1257). The companion's absolute
photometry suggests its mass and atmosphere are similar to the HR 8799 planets.
However, as a wide companion to a late-type star, it is more accessible to
spectroscopic characterization. We discovered that the primary of this system
is an equal-magnitude binary. For an age Myr the A and B components
each have a mass of , and the b component
has a mass of , making VHS 1256-1257 only the third brown
dwarf triple system. There exists some tension between the spectrophotometric
distance of pc and the parallax distance of pc. At
12.7 pc VHS1256-1257 A and B would be the faintest known M7.5 objects, and are
even faint outliers among M8 types. If the larger spectrophotmetric distance is
more accurate than the parallax, then the mass of each component increases. In
particular, the mass of the b component increases well above the deuterium
burning limit to and the mass of each binary
component increases to . At 17.1 pc, the UVW
kinematics of the system are consistent with membership in the AB~Dor moving
group. The architecture of the system resembles a hierarchical stellar multiple
suggesting it formed via an extension of the star-formation process to low
masses. Continued astrometric monitoring will resolve this distance uncertainty
and will provide dynamical masses for a new benchmark system.Comment: Accepted to ApJ
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
- …