769 research outputs found
Mechanical Evidence of the Orbital Angular Momentum to Energy Ratio of Vortex Beams
We measure, in a single experiment, both the radiation pressure and the torque due to a wide variety of
propagating acoustic vortex beams. The results validate, for the first time directly, the theoretically
predicted ratio of the orbital angular momentum to linear momentum in a propagating beam. We
experimentally determine this ratio using simultaneous measurements of both the levitation force and
the torque on an acoustic absorber exerted by a broad range of helical ultrasonic beams produced by a
1000-element matrix transducer array. In general, beams with helical phase fronts have been shown to
contain orbital angular momentum as the result of the azimuthal component of the Poynting vector around
the propagation axis. Theory predicts that for both optical and acoustic helical beams the ratio of the
angular momentum current of the beam to the power should be given by the ratio of the beam’s
topological charge to its angular frequency. This direct experimental observation that the ratio of the
torque to power does convincingly match the expected value (given by the topological charge to angular
frequency ratio of the beam) is a fundamental result
A Search for Exozodiacal Clouds with Kepler
Planets embedded within dust disks may drive the formation of large scale
clumpy dust structures by trapping dust into resonant orbits. Detection and
subsequent modeling of the dust structures would help constrain the mass and
orbit of the planet and the disk architecture, give clues to the history of the
planetary system, and provide a statistical estimate of disk asymmetry for
future exoEarth-imaging missions. Here we present the first search for these
resonant structures in the inner regions of planetary systems by analyzing the
light curves of hot Jupiter planetary candidates identified by the Kepler
mission. We detect only one candidate disk structure associated with KOI 838.01
at the 3-sigma confidence level, but subsequent radial velocity measurements
reveal that KOI 838.01 is a grazing eclipsing binary and the candidate disk
structure is a false positive. Using our null result, we place an upper limit
on the frequency of dense exozodi structures created by hot Jupiters. We find
that at the 90% confidence level, less than 21% of Kepler hot Jupiters create
resonant dust clumps that lead and trail the planet by ~90 degrees with optical
depths >~5*10^-6, which corresponds to the resonant structure expected for a
lone hot Jupiter perturbing a dynamically cold dust disk 50 times as dense as
the zodiacal cloud.Comment: 22 pages, 6 figures, Accepted for publication in Ap
Determination Of The Orbit Of The Planetary Companion To The Metal Rich Star HD 45350
We present the precise radial velocity (RV) data for the metal-rich star HD
45350 collected with the Harlan J. Smith (HJS) 2.7 m telescope and the
Hobby-Eberly Telescope (HET) at McDonald Observatory. This star was noticed by
us as a candidate for having a giant planetary companion in a highly eccentric
orbit, but the lack of data close to periastron left the amplitude and thus
mass of the planet poorly constrained. Marcy et al. (2005) announced the
presence of the planet based on their Keck/HIRES data, but those authors also
cautioned that the remaining uncertainties in the orbital solution might be
large due to insufficient data near periastron passage. In order to close this
phase gap we exploited the flexible queue scheduled observing mode of the HET
to obtain intensive coverage of the most recent periastron passage of the
planet. In combination with the long term data from the HJS 2.7 m telescope we
determine a Keplerian orbital solution for this system with a period of 962
days, an eccentricity of e=0.76 and a velocity semi-amplitude K of 57.4 m/s.
The planet has a minimum mass of m sin i = 1.82 +- 0.14 M_Jup and an orbital
semi-major axis of a = 1.92 +-0.07 AU.Comment: 9 pages preprint, 4 figures, accepted in A
A Planetary Companion to gamma Cephei A
We report on the detection of a planetary companion in orbit around the
primary star of the binary system Cephei. High precision radial
velocity measurements using 4 independent data sets spanning the time interval
1981--2002 reveal long-lived residual radial velocity variations superimposed
on the binary orbit that are coherent in phase and amplitude with a period or
2.48 years (906 days) and a semi-amplitude of 27.5 m s. We performed a
careful analysis of our Ca II H & K S-index measurements, spectral line
bisectors, and {\it Hipparcos} photometry. We found no significant variations
in these quantities with the 906-d period. We also re-analyzed the Ca II
8662 {\AA} measurements of Walker et al. (1992) which showed possible
periodic variations with the ``planet'' period when first published. This
analysis shows that periodic Ca II equivalent width variations were only
present during 1986.5 -- 1992 and absent during 1981--1986.5. Furthermore, a
refined period for the Ca II 8662 {\AA} variations is 2.14 yrs,
significantly less than residual radial velocity period. The most likely
explanation of the residual radial velocity variations is a planetary mass
companion with sin = 1.7 and an orbital semi-major axis
of 2.13 AU. This supports the planet hypothesis for the residual
radial velocity variations for Cep first suggested by Walker et al.
(1992). With an estimated binary orbital period of 57 years Cep is the
shortest period binary system in which an extrasolar planet has been found.
This system may provide insights into the relationship between planetary and
binary star formation.Comment: 19 pages, 15 figures, accepted in Ap. J. Includes additional data and
improved orbital solutio
Brief of Amicus Curiae Professors Elizabeth A. Clark, Robert F. Cochran, Jr., Carl H. Esbeck, David F. Forte, Richard W. Garnett, Christopher C. Lund, Michael W. McConnell, Michael P. Moreland, Robert J. Pushaw, and David A., Skeel, Supporting Petitioners
The case concerns the church autonomy doctrine based on the Free Exercise Clause of the First Amendment, which declares that courts may not inquire into matters of church government or into disputes of faith and doctrine. Will McRaney was fired from a leadership position in the Southern Baptist Convention because of a conflict over policies relating to the expansion of the Baptist faith. He sued the Southern Baptist Convention in tort.
The district court dismissed the suit on the grounds of the church autonomy doctrine. The Fifth Circuit reversed the district court\u27s dismissal as premature, asserting that there were possible neutral principles of law independent of the church autonomy doctrine that might be applicable to the case. The amicus brief in support of a petition of certiorari to the Supreme Court argues that the district court was correct in determining that the church autonomy doctrine requires dismissal of the suit
Compendium of Current Total Ionizing Dose and Displacement Damage Results from NASA GSFC and NEPP
Total ionizing dose and displacement damage testing was performed to characterize and determine the suitability of candidate electronics for NASA space utilization. Devices tested include opto-electronics, digital, analog, linear bipolar devices, and hybrid devices
NASA Goddard Space Flight Center's Compendium of Recent Total Ionizing Dose and Displacement Damage Dose Results
Total ionizing dose and displacement damage dose testing were performed to characterize and determine the suitability of candidate electronics for NASA spacecraft and program use
Persistent starspot signals on M dwarfs: multi-wavelength Doppler observations with the Habitable-zone Planet Finder and Keck/HIRES
Young, rapidly-rotating M dwarfs exhibit prominent starspots, which create
quasiperiodic signals in their photometric and Doppler spectroscopic
measurements. The periodic Doppler signals can mimic radial velocity (RV)
changes expected from orbiting exoplanets. Exoplanets can be distinguished from
activity-induced false positives by the chromaticity and long-term incoherence
of starspot signals, but these qualities are poorly constrained for
fully-convective M stars. Coherent photometric starspot signals on M dwarfs may
persist for hundreds of rotations, and the wavelength dependence of starspot RV
signals may not be consistent between stars due to differences in their
magnetic fields and active regions. We obtained precise multi-wavelength RVs of
four rapidly-rotating M dwarfs (AD Leo, G 227-22, GJ 1245B, GJ 3959) using the
near-infrared (NIR) Habitable-zone Planet Finder, and the optical Keck/HIRES
spectrometer. Our RVs are complemented by photometry from Kepler, TESS, and the
Las Cumbres Observatory (LCO) network of telescopes. We found that all four
stars exhibit large spot-induced Doppler signals at their rotation periods, and
investigated the longevity and optical-to-NIR chromaticity for these signals.
The phase curves remain coherent much longer than is typical for Sunlike stars.
Their chromaticity varies, and one star (GJ 3959) exhibits optical and NIR RV
modulation consistent in both phase and amplitude. In general, though, we find
that the NIR amplitudes are lower than their optical counterparts. We conclude
that starspot modulation for rapidly-rotating M stars frequently remains
coherent for hundreds of stellar rotations, and gives rise to Doppler signals
that, due to this coherence, may be mistaken for exoplanets.Comment: Accepted for publication in the Astrophysical Journa
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