445 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
Demonstration of an automated CFD system for three-dimensional flow simulations
In this paper the capabilities of an automated CFD system which is currently available at NLR are demonstrated. Transonic flow around the AS28G wing/body configuration and hypersonic flow through a generic three-dimensional mixed-compression airbreathing inlet are simulated. An assessment of the level of automation of the current CFD-system is made. The problem-turnaround time lies within the order of a week for both applications
Kepler-445, Kepler-446 And The Occurrence Of Compact Multiples Orbiting Mid-M Dwarf Stars
We confirm and characterize the exoplanetary systems Kepler-445 and Kepler-446: two mid-M dwarf stars, each with multiple, small, short-period transiting planets. Kepler-445 is a metal-rich ([ Fe/H] = + 0.25 0.10) M4 dwarf with three transiting planets, and Kepler-446 is a metal-poor ([ Fe/H] = -0.30 0.10) M4 dwarf also with three transiting planets. Kepler-445c is similar toGJ 1214b: both in planetary radius and the properties of the host star. The Kepler-446 system is similar to the Kepler-42 system: both are metal-poor with large galactic space velocities and three short-period, likely rocky transiting planets that were initially assigned erroneously large planet-to-star radius ratios. We independently determined stellar parameters from spectroscopy and searched for and fitted the transit light curves for the planets, imposing a strict prior on stellar density in order to remove correlations between the fitted impact parameter and planet-to-star radius ratio for short-duration transits. Combining Kepler-445, Kepler-446, and Kepler-42, and isolating all mid-M dwarf stars observed by Kepler with the precision necessary to detect similar systems, we calculate that 21+ 7 -5 % of mid-M dwarf stars host compact multiples ( multiple planets with periods of less than 10 days) for a wide range of metallicities. We suggest that the inferred planet masses for these systems support highly efficient accretion of protoplanetary disk metals by mid-M dwarf protoplanets.NSF DGE1144152, AST-1005313NASA NAS5-26555NASA Office of Space Science NNX13AC07GAstronom
K2-231 b: A sub-Neptune exoplanet transiting a solar twin in Ruprecht 147
We identify a sub-Neptune exoplanet ( R)
transiting a solar twin in the Ruprecht 147 star cluster (3 Gyr, 300 pc, [Fe/H]
= +0.1 dex). The ~81 day light curve for EPIC 219800881 (V = 12.71) from K2
Campaign 7 shows six transits with a period of 13.84 days, a depth of ~0.06%,
and a duration of ~4 hours. Based on our analysis of high-resolution MIKE
spectra, broadband optical and NIR photometry, the cluster parallax and
interstellar reddening, and isochrone models from PARSEC, Dartmouth, and MIST,
we estimate the following properties for the host star: M, R, and K. This star appears to be single, based on our modeling of the
photometry, the low radial velocity variability measured over nearly ten years,
and Keck/NIRC2 adaptive optics imaging and aperture-masking interferometry.
Applying a probabilistic mass-radius relation, we estimate that the mass of
this planet is M, which would cause a RV
semi-amplitude of m s that may be measurable with existing
precise RV facilities. After statistically validating this planet with BLENDER,
we now designate it K2-231 b, making it the second sub-stellar object to be
discovered in Ruprecht 147 and the first planet; it joins the small but growing
ranks of 23 other planets found in open clusters.Comment: 24 pages, 7 figures, light curve included as separate fil
High-resolution broadband spectroscopy using externally dispersed interferometry at the Hale telescope: Part 1, data analysis and results
High-resolution broadband spectroscopy at near-infrared wavelengths (950 to 2450 nm) has been performed using externally dispersed interferometry (EDI) at the Hale telescope at Mt. Palomar. Observations of stars were performed with the “TEDI” interferometer mounted within the central hole of the 200-in. primary mirror in series with the comounted TripleSpec near-infrared echelle spectrograph. These are the first multidelay EDI demonstrations on starlight, as earlier measurements used a single delay or laboratory sources. We demonstrate very high (10×) resolution boost, from original 2700 to 27,000 with current set of delays (up to 3 cm), well beyond the classical limits enforced by the slit width and detector pixel Nyquist limit. Significantly, the EDI used with multiple delays rather than a single delay as used previously yields an order of magnitude or more improvement in the stability against native spectrograph point spread function (PSF) drifts along the dispersion direction. We observe a dramatic (20×) reduction in sensitivity to PSF shift using our standard processing. A recently realized method of further reducing the PSF shift sensitivity to zero is described theoretically and demonstrated in a simple simulation which produces a 350× times reduction. We demonstrate superb rejection of fixed pattern noise due to bad detector pixels—EDI only responds to changes in pixel intensity synchronous to applied dithering. This part 1 describes data analysis, results, and instrument noise. A section on theoretical photon limited sensitivity is in a companion paper, part 2
Precise Stellar Radial Velocities of an M Dwarf with a Michelson Interferometer and a Medium-resolution Near-infrared Spectrograph
Precise near-infrared radial velocimetry enables efficient detection and
transit verification of low-mass extrasolar planets orbiting M dwarf hosts,
which are faint for visible-wavelength radial velocity surveys. The TripleSpec
Exoplanet Discovery Instrument, or TEDI, is the combination of a variable-delay
Michelson interferometer and a medium-resolution (R=2700) near-infrared
spectrograph on the Palomar 200" Hale Telescope. We used TEDI to monitor GJ
699, a nearby mid-M dwarf, over 11 nights spread across 3 months. Analysis of
106 independent observations reveals a root-mean-square precision of less than
37 m/s for 5 minutes of integration time. This performance is within a factor
of 2 of our expected photon-limited precision. We further decompose the
residuals into a 33 m/s white noise component, and a 15 m/s systematic noise
component, which we identify as likely due to contamination by telluric
absorption lines. With further development this technique holds promise for
broad implementation on medium-resolution near-infrared spectrographs to search
for low-mass exoplanets orbiting M dwarfs, and to verify low-mass transit
candidates.Comment: 55 pages and 13 figures in aastex format. Accepted by PAS
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