2,178 research outputs found
Bayesian analysis of the radial velocities of HD 11506 reveals another planetary companion
We aim to demonstrate the efficiency of a Bayesian approach in analysing
radial velocity data by reanalysing a set of radial velocity measurements. We
present Bayesian analysis of a recently published set of radial velocity
measurements known to contain the signal of one extrasolar planetary candidate,
namely, HD 11506. The analysis is conducted using the Markov chain Monte Carlo
method and the resulting distributions of orbital parameters are tested by
performing direct integration of randomly selected samples with the
Bulirsch-Stoer method. The magnitude of the stellar radial velocity
variability, known as jitter, is treated as a free parameter with no
assumptions about its magnitude. We show that the orbital parameters of the
planet known to be present in the data correspond to a different solution when
the jitter is allowed to be a free parameter. We also show evidence of an
additional candidate, a 0.8 MJup planet with period of about 0.5 yr in orbit
around HD 11506. This second planet is inferred to be present with a high level
of confidence.Comment: 4 pages, 5 figures, to appear in A&
A determination of the spin-orbit alignment of the anomalously dense planet orbiting HD 149026
We report 35 radial velocity measurements of HD 149026 taken with the Keck Telescope. Of these measurements, 15
were made during the transit of the companion planet HD 149026b, which occurred on 2005 June 25. These velocities
provide a high-cadence observation of the Rossiter-McLaughlin effect, the shifting of photospheric line profiles that occurs when a planet occults a portion of the rotating stellar surface. We combine these radial velocities with previously published radial velocity and photometric data sets and derive a composite best-fit model for the star-planet system. This model confirms and improves previously published orbital parameters, including the remarkably small planetary radius, the planetary mass, and the orbital inclination, found to be Rp/RJup = 0.718 ± 0.065, Mp/MJup = 0.352 ± 0.025, and I = 86.1° ± 1.4°, respectively. Together the planetary mass and radius determinations imply a mean planetary density
of 1.18(-0.30)(+0.38)g cm(-3). The new data also allow for the determination of the angle between the apparent stellar equator and the orbital plane, which we constrain to be λ = -12° ± 15°
Two Jovian-Mass Planets in Earthlike Orbits
We report the discovery of two new planets: a 1.94 M_Jup planet in a 1.8-year
orbit of HD 5319, and a 2.51 M_Jup planet in a 1.1-year orbit of HD 75898. The
measured eccentricities are 0.12 for HD 5319 b and 0.10 for HD 75898 b, and
Markov Chain Monte Carlo simulations based on derived orbital parameters
indicate that the radial velocities of both stars are consistent with circular
planet orbits. With low eccentricity and 1 < a < 2 AU, our new planets have
orbits similar to terrestrial planets in the solar system. The radial velocity
residuals of both stars have significant trends, likely arising from substellar
or low-mass stellar companions.Comment: 32 pages, including 11 figures and 5 tables. Accepted by Ap
Combining Psychological and Engineering Approaches to Utilizing Social Robots with Children with Autism
Abstract-It is estimated that Autism Spectrum Disorder (ASD) affects 1 in 68 children
Identifying Very Metal-Rich Stars with Low-Resolution Spectra: Finding Planet-Search Targets
We present empirical calibrations that estimate stellar metallicity,
effective temperature and surface gravity as a function of Lick/IDS indices.
These calibrations have been derived from a training set of 261 stars for which
(1) high-precision measurements of [Fe/H], T_eff and log g have been made using
spectral-synthesis analysis of HIRES spectra, and (2) Lick indices have also
been measured. Our [Fe/H] calibration, which has precision 0.07 dex, has
identified a number of bright (V < 9) metal-rich stars which are now being
screened for hot Jupiter-type planets. Using the Yonsei-Yale stellar models, we
show that the calibrations provide distance estimates accurate to 20% for
nearby stars.
This paper outlines the second tier of the screening of planet-search targets
by the N2K Consortium, a project designed to identify the stars most likely to
harbor extrasolar planets. Discoveries by the N2K Consortium include the
transiting hot Saturn HD 149026 b (Sato et al. 2005, astro-ph/0507009) and HD
88133 b (Fischer et al. 2005). See Ammons et al. (2005, In Press) for a
description of the first tier of N2K metallicity screening, calibrations using
broadband photometry.Comment: Accepted for publication in the Astrophysical Journa
Combining data from the distributed GRUAN site Lauder-Invercargill, New Zealand, to provide a site atmospheric state best estimate of temperature
A site atmospheric state best estimate (SASBE) of the temperature profile above the GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN) site at Lauder, New Zealand, has been developed. Data from multiple sources are combined within the SASBE to generate a high temporal resolution data set that includes an estimate of the uncertainty on every value.
The SASBE has been developed to enhance the value of measurements made at the distributed GRUAN site at Lauder and Invercargill (about 180km apart), and to demonstrate a methodology which can be adapted to other distributed sites. Within GRUAN, a distributed site consists of a cluster of instruments at different locations.
The temperature SASBE combines measurements from radiosondes and automatic weather stations at Lauder and Invercargill, and ERA5 reanalysis, which is used to calculate a diurnal temperature cycle to which the SASBE converges in the absence of any measurements.
The SASBE provides hourly temperature profiles at 16 pressure levels between the surface and 10hPa for the years 1997 to 2012. Every temperature value has an associated uncertainty which is calculated by propagating the measurement uncertainties, the ERA5 ensemble standard deviations, and the ERA5 representativeness uncertainty through the retrieval chain. The SASBE has been long-term archived and is identified using the digital object identifier https://doi.org/10.5281/zenodo.1195779.
The study demonstrates a method to combine data collected at distributed sites. The resulting best-estimate temperature data product for Lauder is expected to be valuable for satellite and model validation as measurements of atmospheric essential climate variables are sparse in the Southern Hemisphere. The SASBE could, for example, be used to constrain a radiative transfer model to provide top-of-the-atmosphere radiances with traceable uncertainty estimates
The NASA-UC-UH Eta-Earth Program: IV. A Low-mass Planet Orbiting an M Dwarf 3.6 PC from Earth
We report the discovery of a low-mass planet orbiting Gl 15 A based on radial
velocities from the Eta-Earth Survey using HIRES at Keck Observatory. Gl 15 Ab
is a planet with minimum mass Msini = 5.35 0.75 M, orbital
period P = 11.4433 0.0016 days, and an orbit that is consistent with
circular. We characterize the host star using a variety of techniques.
Photometric observations at Fairborn Observatory show no evidence for
rotational modulation of spots at the orbital period to a limit of ~0.1 mmag,
thus supporting the existence of the planet. We detect a second RV signal with
a period of 44 days that we attribute to rotational modulation of stellar
surface features, as confirmed by optical photometry and the Ca II H & K
activity indicator. Using infrared spectroscopy from Palomar-TripleSpec, we
measure an M2 V spectral type and a sub-solar metallicity ([M/H] = -0.22,
[Fe/H] = -0.32). We measure a stellar radius of 0.3863 0.0021 R
based on interferometry from CHARA.Comment: ApJ accepted, 11 pages, 8 figures, 3 table
Survey of J=0,1 mesons in a Bethe-Salpeter approach
The Bethe-Salpeter equation is used to comprehensively study mesons with
J=0,1 and equal-mass constituents for quark masses from the chiral limit to the
b-quark mass. The survey contains masses of the ground states in all
corresponding J^{PC} channels including those with "exotic" quantum numbers.
The emphasis is put on each particular state's sensitivity to the low- and
intermediate-momentum, i.e., long-range part of the strong interaction.Comment: 8 pages, 4 figure
Five Intermediate-Period Planets from the N2K Sample
We report the detection of five Jovian mass planets orbiting high metallicity
stars. Four of these stars were first observed as part of the N2K program and
exhibited low RMS velocity scatter after three consecutive observations.
However, follow-up observations over the last three years now reveal the
presence of longer period planets with orbital periods ranging from 21 days to
a few years. HD 11506 is a G0V star with a planet of \msini = 4.74 \mjup in a
3.85 year orbit. HD 17156 is a G0V star with a 3.12 \mjup planet in a 21.2 day
orbit. The eccentricity of this orbit is 0.67, one of the highest known for a
planet with a relatively short period. The orbital period for this planet
places it in a region of parameter space where relatively few planets have been
detected. HD 125612 is a G3V star with a planet of \msini = 3.5 \mjup in a 1.4
year orbit. HD 170469 is a G5IV star with a planet of \msini = 0.67 \mjup in a
3.13 year orbit. HD 231701 is an F8V star with planet of 1.08 \mjup in a 142
day orbit. All of these stars have supersolar metallicity. Three of the five
stars were observed photometrically but showed no evidence of brightness
variability. A transit search conducted for HD 17156 was negative but covered
only 25% of the search space and so is not conclusive.Comment: 13 pages, 9 figures, accepted ApJ Resubmitted here with some
additional data, modified Keplerian orbit
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