High-Spatial-Resolution K-Band Imaging of Select K2 Campaign Fields

NASA's K2 mission began observing fields along the ecliptic plane in 2014. Each observing campaign lasts approximately 80 days, during which high-precision optical photometry of select astrophysical targets is collected by the Kepler spacecraft. Due to the 4 arcsec pixel scale of the Kepler photometer, significant blending between the observed targets can occur (especially in dense fields close to the Galactic plane). We undertook a program to use the Wide Field Camera (WFCAM) on the 3.8 m United Kingdom InfraRed Telescope (UKIRT) to collect high-spatial-resolution near-infrared images of targets in select K2 campaign fields, which we report here. These 0.4 arcsec resolution K-band images offer the opportunity to perform a variety of science, including vetting exoplanet candidates by identifying nearby stars blended with the target star and estimating the size, color, and type of galaxies observed by K2.Comment: 2 pages, Published by Research Notes of the American Astronomical Societ

Three-dimensional ambient noise modeling in a submarine canyon

Author Posting. © Acoustical Society of America, 2019. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 146(3), (2019): 1956-1967, doi:10.1121/1.5125589.A quasi-analytical three-dimensional (3D) normal mode model for longitudinally invariant environments can be used to compute vertical noise coherence in idealized ocean environments. An examination of the cross modal amplitudes in the modal decomposition of the noise cross-spectral density shows that the computation can be simplified, without loss of fidelity, by modifying the vertical and horizontal mode sums to exclude non-identical mode numbers. In the special case of a Gaussian canyon, the across-canyon variation of the vertical wave number associated with each mode allows a set of horizontally trapped modes to be generated. Full 3D and Nx2D parabolic equation sound propagation models can also be used to calculate vertical noise coherence and horizontal directionality. Intercomparison of these models in idealized and realistic canyon environments highlights the focusing effect of the bathymetry on the noise field. The absolute vertical noise coherence increases, while the zero-crossings of the real component of the coherence are displaced in frequency when out-of-plane propagation is accounted for.The authors wish to acknowledge Arthur Newhall for his technical support. This work was supported by the Office of Naval Research, Ocean Acoustic Code 322OA, under Grant Nos. N00014-15-1-2629 and N00014-17-1-2692, and by the Natural Sciences and Engineering Research Council of Canada's Research Chair, and Discovery Grant program.2020-03-3

Implosion in the Challenger Deep: echo sounding with the shock wave

© The Author(s), 2021. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Loranger, S., Barclay, D., & Buckingham, M. Implosion in the Challenger Deep: echo sounding with the shock wave. Oceanography, 34(2), (2021), https://doi.org/10.5670/oceanog.2021.201.Since HMS Challenger made the first sounding in the Mariana Trench in 1875, scientists and explorers have been seeking to establish the exact location and depth of the deepest part of the ocean. The scientific consensus is that the deepest depth is situated in the Challenger Deep, an abyss in the Mariana Trench with depths greater than 10,000 m. Since1952, when HMS Challenger II, following its namesake, returned to the Mariana Trench, 20 estimates (including the one from this study) of the depth of the Challenger Deep have been made. The location and depth estimates are as diverse as the methods used to obtain them; they range from early measurements with explosives and stopwatches, to single- and multibeam sonars, to submersibles, both crewed and remotely operated. In December 2014, we participated in an expedition to the Challenger Deep onboard Schmidt Ocean Institute’s R/V Falkor and deployed two free-falling, passive-acoustic instrument platforms, each with a glass-sphere pressure housing containing system electronics. At a nominal depth of 9,000 m, one of these housings imploded, creating a highly energetic shock wave that, as recorded by the other instrument, reflected multiple times from the sea surface and seafloor. From the arrival times of these multi-path pulses at the surviving instrument, in conjunction with a concurrent measurement of the sound speed profile in the water column, we obtained a highly constrained acoustic estimate of the Challenger Deep: 10,983 ± 6 m.This work was funded by the Schmidt Ocean Institute, the Ocean Frontiers Institute, and the Office of Naval Research, Ocean Acoustics, Code 322OA, grant number N00014-18-1-2126

Quantifying the contribution of ship noise to the underwater sound field

Author Posting. © Acoustical Society of America, 2020. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 148(6), (2020): 3863-3872, https://doi.org/10.1121/10.0002922.The ambient sound field in the ocean can be decomposed into a linear combination of two independent fields attributable to wind-generated wave action at the surface and noise radiated by ships. The vertical coherence (the cross-spectrum normalized by the power spectra) and normalized directionality of wind-generated noise in the ocean are stationary in time, do not vary with source strength and spectral characteristics, and depend primarily on the local sound speed and the geoacoustic properties which define the propagation environment. The contribution to the noise coherence due to passing vessels depends on the range between the source and receiver, the propagation environment, and the effective bandwidth of the characteristic source spectrum. Using noise coherence models for both types of the sources, an inversion scheme is developed for the relative and absolute contribution of frequency dependent ship noise to the total sound field. A month-long continuous ambient sound recording collected on a pair of vertically aligned hydrophones near Alvin Canyon at the New England shelf break is decomposed into time-dependent ship noise and wind-driven noise power spectra. The processing technique can be used to quantify the impact of human activity on the sound field above the natural dynamic background noise, or to eliminate ship noise from a passive acoustic monitoring data set.The work was funded by Office of Naval Research, Code 32 (Grant No. N00014-17-1-2692 for Y.T. Lin), and the Canada Research Chair program and the Natural Science and Engineering Research Council Discovery program. N. S. would like to thank Transatlantic Ocean System Science and Technology (TOSST) for his graduate fellowship.2021-06-2

The Five Planets in the Kepler-296 Binary System All Orbit the Primary: A Statistical and Analytical Analysis

Kepler-296 is a binary star system with two M-dwarf components separated by 0.2 arcsec. Five transiting planets have been confirmed to be associated with the Kepler-296 system; given the evidence to date, however, the planets could in principle orbit either star. This ambiguity has made it difficult to constrain both the orbital and physical properties of the planets. Using both statistical and analytical arguments, this paper shows that all five planets are highly likely to orbit the primary star in this system. We performed a Markov-Chain Monte Carlo simulation using a five transiting planet model, leaving the stellar density and dilution with uniform priors. Using importance sampling, we compared the model probabilities under the priors of the planets orbiting either the brighter or the fainter component of the binary. A model where the planets orbit the brighter component, Kepler-296A, is strongly preferred by the data. Combined with our assertion that all five planets orbit the same star, the two outer planets in the system, Kepler-296 Ae and Kepler-296 Af, have radii of 1.53 +/- 0.26 and 1.80 +/- 0.31 R_earth, respectively, and receive incident stellar fluxes of 1.40 +/- 0.23 and 0.62 +/- 0.10 times the incident flux the Earth receives from the Sun. This level of irradiation places both planets within or close to the circumstellar habitable zone of their parent star.Comment: Accepted for publication in Ap

Dissipative and Dispersive Optomechanics in a Nanocavity Torque Sensor

Dissipative and dispersive optomechanical couplings are experimentally observed in a photonic crystal split-beam nanocavity optimized for detecting nanoscale sources of torque. Dissipative coupling of up to approximately $500$ MHz/nm and dispersive coupling of $2$ GHz/nm enable measurements of sub-pg torsional and cantilever-like mechanical resonances with a thermally-limited torque detection sensitivity of 1.2$\times 10^{-20} \text{N} \, \text{m}/\sqrt{\text{Hz}}$ in ambient conditions and 1.3$\times 10^{-21} \text{N} \, \text{m}/\sqrt{\text{Hz}}$ in low vacuum. Interference between optomechanical coupling mechanisms is observed to enhance detection sensitivity and generate a mechanical-mode-dependent optomechanical wavelength response.Comment: 11 pages, 6 figure

High-resolution Multi-band Imaging for Validation and Characterization of Small Kepler Planets

High-resolution ground-based optical speckle and near-infrared adaptive optics images are taken to search for stars in close angular proximity to host stars of candidate planets identified by the NASA Kepler Mission. Neighboring stars are a potential source of false positive signals. These stars also blend into Kepler light curves, affecting estimated planet properties, and are important for an understanding of planets in multiple star systems. Deep images with high angular resolution help to validate candidate planets by excluding potential background eclipsing binaries as the source of the transit signals. A study of 18 Kepler Object of Interest stars hosting a total of 28 candidate and validated planets is presented. Validation levels are determined for 18 planets against the likelihood of a false positive from a background eclipsing binary. Most of these are validated at the 99% level or higher, including 5 newly-validated planets in two systems: Kepler-430 and Kepler-431. The stellar properties of the candidate host stars are determined by supplementing existing literature values with new spectroscopic characterizations. Close neighbors of 7 of these stars are examined using multi-wavelength photometry to determine their nature and influence on the candidate planet properties. Most of the close neighbors appear to be gravitationally-bound secondaries, while a few are best explained as closely co-aligned field stars. Revised planet properties are derived for each candidate and validated planet, including cases where the close neighbors are the potential host stars.Comment: in press at AJ, 44 pages, 8 figures; The only changes made relative to version 1 are updates to the list of reference

On the indistinguishability of Raman photons

We provide a theoretical framework to study the effect of dephasing on the quantum indistinguishability of single photons emitted from a coherently driven cavity QED $\Lambda$-system. We show that with a large excited-state detuning, the photon indistinguishability can be drastically improved provided that the fluctuation rate of the noise source affecting the excited state is fast compared with the photon emission rate. In some cases a spectral filter is required to realize this improvement, but the cost in efficiency can be made small.Comment: 18 pages, 3 figures, final versio