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A Large Double-ring Disk Around the Taurus M Dwarf J04124068+2438157
No full textPlanet formation imprints signatures on the physical structures of disks. In this paper, we present high-resolution (∼50 mas, 8 au) Atacama Large Millimeter/submillimeter Array observations of 1.3 mm dust continuum and CO line emission toward the disk around the M3.5 star 2MASS J04124068+2438157. The dust disk consists of only two narrow rings at radial distances of 0.”47 and 0.”78 (∼70 and 116 au), with Gaussian σ widths of 5.6 and 8.5 au, respectively. The width of the outer ring is smaller than the estimated pressure scale height by ∼25%, suggesting dust trapping in a radial pressure bump. The dust disk size, set by the location of the outermost ring, is significantly larger (by 3σ) than other disks with similar millimeter luminosity, which can be explained by an early formation of local pressure bump to stop radial drift of millimeter dust grains. After considering the disk's physical structure and accretion properties, we prefer planet–disk interaction over dead zone or photoevaporation models to explain the observed dust disk morphology. We carry out high-contrast imaging at the L’ band using Keck/NIRC2 to search for potential young planets, but do not identify any source above 5σ. Within the dust gap between the two rings, we reach a contrast level of ∼7 mag, constraining the possible planet below ∼2–4 M_(Jup). Analyses of the gap/ring properties suggest that an approximately Saturn-mass planet at ∼90 au is likely responsible for the formation of the outer ring, which can potentially be revealed with JWST
A hard look at the X-ray spectral variability of NGC 7582
No full textNGC 7582 (z = 0.005264; D = 22.5 Mpc) is a highly variable, changing-look AGN. In this work, we explore the X-ray properties of this source using XMM–Newton and NuSTAR archival observations in the 3 – 40 keV range, from 2001 to 2016. NGC 7582 exhibits a long-term variability between observations but also a short-term variability in two observations that has not been studied before. To study the variability, we perform a time-resolved spectral analysis using a phenomenological model and a physically motivated model (uxclumpy). The spectral fitting is achieved using a nested sampling Monte Carlo method. uxclumpy enables testing various geometries of the absorber that may fit AGN spectra. We find that the best model is composed of a fully covering clumpy absorber. From this geometry, we estimate the velocity, size, and distance of the clumps. The column density of the absorber in the line of sight varies from Compton-thin to Compton-thick between observations. Variability over the time-scale of a few tens of kiloseconds is also observed within two observations. The obscuring clouds are consistent with being located at a distance not larger than 0.6 pc, moving with a transverse velocity exceeding ∼700 km s⁻¹. We could put only a lower limit on the size of the obscuring cloud being larger than 10¹³ cm. Given the sparsity of the observations, and the limited exposure time per observation available, we cannot determine the exact structure of the obscuring clouds. The results are broadly consistent with comet-like obscuring clouds or spherical clouds with a non-uniform density profile
General relativistic simulations of collapsing binary neutron star mergers with Monte Carlo neutrino transport
No full textRecent gravitational wave observations of neutron-star-neutron-star and neutron-star-black-hole binaries appear to indicate that massive neutron stars may not be too uncommon in merging systems. These discoveries have led to an increased interest in the simulation of merging compact binaries involving massive stars. In this paper, we present a first set of evolution of massive neutron star binaries using Monte Carlo radiation transport for the evolution of neutrinos. We study a range of systems, from nearly symmetric binaries that collapse to a black hole before forming a disk or ejecting material, to more asymmetric binaries in which tidal disruption of the lower mass star leads to the production of more interesting postmerger remnants. For the latter type of systems, we additionally study the impact of viscosity on the properties of the outflows, and compare our results to two recent simulations of identical binaries performed with the whiskythc code. We find agreement on the black hole properties, disk mass, and mass and velocity of the outflows within expected numerical uncertainties, and some minor but noticeable differences in the evolution of the electron fraction when using a subgrid viscosity model, with viscosity playing a more minor role in our simulations. The method used to account for r-process heating in the determination of the outflow properties appears to have a larger impact on our result than those differences between numerical codes. We also use the simulation with the most ejected material to verify that our newly implemented Lagrangian tracers provide a reasonable sampling of the matter outflows as they leave the computational grid. We note that, given the lack of production of hot outflows in these mergers, the main role of neutrinos in these systems is to set the composition of the postmerger remnant. One of the main potential uses of our simulations is, thus, as improved initial conditions for longer evolutions of such remnants
Control education for societal-scale challenges: A community roadmap
No full textThis article focuses on extending, disseminating and interpreting the findings of an IEEE Control Systems Society working group looking at the role of control theory and engineering in solving some of the many current and future societal challenges. The findings are interpreted in a manner designed to give focus and direction to both future education and research work in the general control theory and engineering arena, interpreted in the broadest sense. The paper is intended to promote discussion in the community and also provide a useful starting point for colleagues wishing to re-imagine the design and delivery of control-related topics in our education systems, especially at the tertiary level and beyond
The TESS-Keck Survey. XV. Precise Properties of 108 TESS Planets and Their Host Stars
No full textWe present the stellar and planetary properties for 85 TESS Objects of Interest (TOIs) hosting 108 planet candidates that compose the TESS-Keck Survey (TKS) sample. We combine photometry, high-resolution spectroscopy, and Gaia parallaxes to measure precise and accurate stellar properties. We then use these parameters as inputs to a light-curve processing pipeline to recover planetary signals and homogeneously fit their transit properties. Among these transit fits, we detect significant transit-timing variations among at least three multiplanet systems (TOI-1136, TOI-1246, TOI-1339) and at least one single-planet system (TOI-1279). We also reduce the uncertainties on planet-to-star radius ratios R_p/R⋆ across our sample, from a median fractional uncertainty of 8.8% among the original TOI Catalog values to 3.0% among our updated results. With this improvement, we are able to recover the Radius Gap among small TKS planets and find that the topology of the Radius Gap among our sample is broadly consistent with that measured among Kepler planets. The stellar and planetary properties presented here will facilitate follow-up investigations of both individual TOIs and broader trends in planet properties, system dynamics, and the evolution of planetary systems
Using a Bayesian-Inference Approach to Calibrating Models for Simulation in Robotics
No full textIn robotics, simulation has the potential to reduce design time and costs, and lead to a more robust engineered solution and a safer development process. However, the use of simulators is predicated on the availability of good models. This contribution is concerned with improving the quality of these models via calibration, which is cast herein in a Bayesian framework. First, we discuss the Bayesian machinery involved in model calibration. Then, we demonstrate it in one example: calibration of a vehicle dynamics model that has low degree-of-freedom (DOF) count and can be used for state estimation, model predictive control, or path planning. A high fidelity simulator is used to emulate the “experiments” and generate the data for the calibration. The merit of this work is not tied to a new Bayesian methodology for calibration, but to the demonstration of how the Bayesian machinery can establish connections among models in computational dynamics, even when the data in use is noisy. The software used to generate the results reported herein is available in a public repository for unfettered use and distribution
Target-oriented elastic full-waveform inversion through acoustic extended image-space redatuming
No full textElastic full-waveform inversion (FWI) can provide accurate and high-resolution subsurface parameters. However, its high computational cost prevents the application of this method to large-scale field-data scenarios. To mitigate this limitation, we have developed a target-oriented elastic FWI methodology based on a redatuming step that relies upon an extended least-squares migration process. In our approach, the surface-reflection data can be attributed to a given subsurface portion when mapped into the image space. This process allows us to reconstruct reflection data generated by a target area and recorded with a virtual acquisition geometry positioned directly above it. The redatuming step enables the application of an elastic FWI method within the target portion only. The entire workflow drastically decreases the overall cost of the surface-data inversion and allows the retrieval of accurate elastic parameters of the area of interest. We determine the effectiveness of our approach on a synthetic case based on the well-known Marmousi2 model and on 3D ocean-bottom node pressure data recorded in the Gulf of Mexico in which we retrieve the elastic parameters of a potential prospect, positioned in proximity of a salt-dome flank, and whose rock-physical properties are consistent with the presence of a gas-bearing sand reservoir
Unification of Thermal and Quantum Noises in Gravitational-Wave Detectors
No full textContemporary gravitational-wave detectors are fundamentally limited by thermal noise—due to dissipation in the mechanical elements of the test mass—and quantum noise—from the vacuum fluctuations of the optical field used to probe the test-mass position. Two other fundamental noises can in principle also limit sensitivity: test-mass quantization noise due to the zero-point fluctuation of its mechanical modes and thermal excitation of the optical field. We use the quantum fluctuation-dissipation theorem to unify all four noises. This unified picture shows precisely when test-mass quantization noise and optical thermal noise can be ignored
New interstellar laboratories in the molecular ring
No full textMuch of what is known about chemistry in star-forming regions comes from observations of nearby (d < 500 pc) low-mass protostars. For chemistry in high-mass star-forming regions, several more distant (d ∼ 2–8 kpc), exceptionally bright molecular sources have also been the subjects of repeated observations but with concomitantly poorer linear spatial resolution. Facilities such as ALMA and JWST, however, now provide the means for observing distant sources at dramatically higher spatial resolution and sensitivity. We used the modest resolving power of the Atacama Compact Array, a dedicated subset of ALMA antennas, to carry out a pilot survey of 11 giant molecular clouds selected from the Bolocam Galactic Plane Survey [Battisti & Heyer, Astrophys. J., 2014, 780, 173] within the so-called molecular ring between about 4 and 8 kpc from the galactic center. Within our observed sample, molecular emission regions—most of which correspond to at least one (candidate) young stellar object—exhibit a range of chemical complexity and diversity. Furthermore, nine target giant molecular clouds contain well-fit methanol emission, giving us a first look at the spatial chemical variability within the objects at relatively high (compared to past observations) resolutions of ∼5′′. This work lays the foundation for future high angular resolution studies of gas-phase chemistry with the full ALMA
Conspiracy spillovers and geoengineering
No full textGeoengineering techniques such as solar radiation management (SRM) could be part of a future technology portfolio to limit global temperature change. However, there is public opposition to research and deployment of SRM technologies. We use 814,924 English-language tweets containing #geoengineering globally over 13 years (2009–2021) to explore public emotions, perceptions, and attitudes toward SRM using natural language processing, deep learning, and network analysis. We find that specific conspiracy theories influence public reactions toward geoengineering, especially regarding “chemtrails” (whereby airplanes allegedly spray poison or modify weather through contrails). Furthermore, conspiracies tend to spillover, shaping regional debates in the UK, USA, India, and Sweden and connecting with broader political considerations. We also find that positive emotions rise on both the global and country scales following events related to SRM governance, and negative and neutral emotions increase following SRM projects and announcements of experiments. Finally, we also find that online toxicity shapes the breadth of spillover effects, further influencing anti-SRM views