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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 1,063 records · Page 59
All sourcesNASA NTRSDOE OSTI
NASA NTRS2019

Highly Charged Ions in a New Era of High Resolution X-Ray Astrophysics

X‐ray astronomy and ground‐based atomic physics have a long history of fruitful collaboration: Sound understanding of the underlying atomic physics is the key to reliable interpretation of the spectra from celestial sources; conversely, astronomical spectra have been used to benchmark and advance atomic physics. This interplay is about to become even more important as we enter a new era of high‐resolution X‐ray astrophysics with large effective collection area. Although high‐resolution observations with the gratings on the Chandra and XMM‐Newton observatories continue to drive new science, upcoming planned and proposed missions will open up new discovery space in the near future that is currently challenging to access: high‐resolution spectroscopy on extended sources, in the Fe K band, and on short time scales. This review summarizes open questions in these areas and the design parameters for the Hitomi, XRISM, Athena, and Arcus observatories. The expected high quality of spectra taken with these observatories puts new constraints on the accuracy of atomic reference data required to take full advantage of the diagnostic potential of these spectra.

Natalie Hell↗
NASA NTRS2019

Plasma environment effects on K lines of astrophysical interest II. Ionization potentials, K thresholds, radiative rates, and Auger widths in Ne- through He-like iron ions (Fe xvii – Fe xxv)

Aims. In the context of accretion disks around black holes, we estimate plasma-environment effects on the atomic parameters associated with the decay of K-vacancy states in highly charged iron ions, namely Fe XVII – Fe XXV. Methods. Within the relativistic multiconfiguration Dirac–Fock (MCDF) framework, the electron–nucleus and electron–electron plasma screenings were approximated with a time-averaged Debye–Hückel potential. Results. Modified ionization potentials, K thresholds, wavelengths, radiative emission rates, and Auger widths are reported for astrophysical plasmas characterized by electron temperatures and densities in the ranges 10^5 − 10^7 K and 10^18 − 10^22 per cu.cm, respectively. Conclusions. We conclude that the high-resolution microcalorimeters on board future X-ray missions such as XRISM and ATHENA are expected to be sensitive to the lowering of the iron K edge due to the extreme plasma conditions occurring in accretion disks around compact objects.

J. Deprince↗
NASA NTRS2020

Properties and Astrophysical Implications of the 150 M Binary Black Hole Merger GW190521

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, 85 (+21,-14) Mꙩ and 66 (+17,-18) Mꙩ, compared to previously reported events, and shows mild evidence for spin-induced orbital precession. The primary falls in the mass gap predicted by (pulsational) pair-instability supernova theory, in the approximate range 65–120 Mꙩ. The probability that at least one of the black holes in GW190521 is in that range is 99.0%. The final mass of the merger (142 (+28,-16) Mꙩ) classifies it as an intermediate-mass black hole. Under the assumption of a quasi-circular BBH coalescence, we detail the physical properties of GW190521’s source binary and its post-merger remnant, including component masses and spin vectors. Three different waveform models, as well as direct comparison to numerical solutions of general relativity, yield consistent estimates of these properties. Tests of strong-field general relativity targeting the merger-ringdown stages of the coalescence indicate consistency of the observed signal with theoretical predictions. We estimate the merger rate of similar systems to be 0.13 (+0.30,-0.11)Gp/cu.c yr. We discuss the astrophysical implications of GW190521 for stellar collapse and for the possible formation of black holes in the pair-instability mass gap through various channels: via (multiple) stellar coalescences, or via hierarchical mergers of lower-mass black holes in star clusters or in active galactic nuclei. We find it to be unlikely that GW190521 is a strongly lensed signal of a lower-mass black hole binary merger. We also discuss more exotic possible sources for GW190521, including a highly eccentric black hole binary, or a primordial black hole binary.

R. Abbott↗
NASA NTRS2019

K-line X-ray fluorescence from highly charged iron ions under dense astrophysical plasma conditions

In the present work, we report an investigation of plasma environment effects on the atomic parameters associated with the K-vacancy states in highly charged iron ions within the astrophysical context of accretion disks around black holes. More particularly, the sensitivity of K-line X-ray fluorescence parameters (wavelengths, radiative transition probabilities, and Auger rates) in Fe XVII–Fe XXV ions has been estimated for plasma conditions characterized by an electron temperature ranging from 105 to 107K and an electron density ranging from 1018 to1022 cm−3. In order to do this, relativistic multiconfiguration Dirac-Fock atomic structure calculations have been carried out by considering a time averaged Debye-Hückel potential for both the electron–nucleus and electron–electron interactions.

Jérôme Deprince↗
NASA NTRS2022

SiAl Composite Feedhorn Arrays for Astrophysical Applications: Cryogenic Material Properties

A study investigating the physical properties and use of the SiAl composite Controlled Expansion 7 (CE7) for the packaging of silicon bolometric detectors for millimeter-wave astrophysical applications at cryogenic temperatures is presented. The existing interfaces to such detectors are typically made of either ductile metals or micro-machined silicon. As a composite of Si and Al, we find that CE7 exhibits properties of both in ways that may be advantageous for this application. This exploration of the physical properties of CE7 reveals: (a) superconductivity below a critical transition temperature, T_c ∼ 1.2 K; (b) a thermal contraction profile much closer to Si than metal substrates; (c) the relatively low thermal conductivity anticipated for a superconductor, which can be improved by Au-plating; and (d) the feasibility of machining mechanical features with tolerances of ∼25 µm. We further discuss the use of CE7 in the cosmology large angular scale surveyor telescope array, which deployed CE7 in several of its detector focal planes.

Aamir M. Ali↗
NASA NTRS2022

The NASA Multi-Messenger Astrophysics Science Support Center (MOSSAIC)*

The era of multi-messenger astrophysics has arrived, leading to key new discoveries and revealing a need for coordination, collab-oration, and communication between world-wide communities using ground and space-based facilities. To fill these critical needs,NASA’s Goddard Space Flight Center and Marshall Space Flight Center are jointly proposing to establish a virtual Multi-MessengerAstrophysics Science Support Center that focuses entirely on community-directed services. In this article, we describe the baselineplan for the virtual Support Center which will position the community and NASA as an Agency to extract maximum science frommulti-messenger events, leading to new breakthroughs and fostering increased coordination and collaboration.

R M Sambruna↗
NASA NTRSDate not supplied

Novel Infrared-blocking Aerogel Scattering Filters and Their Applications in Astrophysical and Planetary Science Observations

Infrared-blocking scattering aerogel filters have a broad range of potential applications in astrophysics and planetary science observations in the far-infrared, sub-millimeter, and microwave regimes. Successful dielectric modeling of aerogel filters allowed the fabrication of samples to meet the mechanical and science instrument requirements for several experiments, including the Sub-millimeter Solar Observation Lunar Volatiles Experiment (SSOLVE), the Cosmology Large Angular Scale Surveyor (CLASS), and the Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM). Thermal multi-physics simulations of the filters predict their performance when integrated into a cryogenic receiver. Prototype filters have survived cryogenic cycling to 4 K with no degradation in mechanical properties.

Kyle R Helson↗
NASA NTRSDate not supplied

PRIMA: The PRobe Far-Infrared Mission for Astrophysics

PRIMA is a far-infrared observatory concept being developed to address timely and fundamental questions about the growths of galaxies and solar systems and their constituents. It will observe the build-up of heavy elements, dust, stars, and black holes in galaxies and their interrelationships, and trace the masses and water contents of protoplanetary disks to probe the growths of solar systems. The majority of observing time will be devoted to Guest Observer programs to enable the astrophysics community to identify and plan the most critical observations, with focused PI programs to address key science with rapid releases of data to inform community planning. PRIMA will have spectral, hyperspectral imaging, and polarimetric capabilities, enabled now for the first time by extraordinary progress in kinetic inductance detector (KID) array technology over the last two decades. The 2.0-meter telescope will be cooled to < 5 K to take maximum advantage of the KID sensitivities. For observations of atomic fine-structure lines, molecular lines, and solid-state emission and absorption bands, R = 200 spectral coverage will range from approximately 25 µm to 200 µm, with a high-resolution mode across the entire band that will have a spectral resolving power of a few thousand at 100 µm. R ~ 10 moderate-resolution (hyperspectral) imaging will range from 25 to 80 µm for rest-frame, mid- and far-infrared spectral energy distribution measurements to probe dust grain composition and disambiguate star formation and active galactic nuclei in galaxies. Polarimetric observations of large areas of Galactic molecular clouds and the Magellanic Clouds from 80 to ~200 µm will bridge between the large-scale polarimetry of the interstellar medium from cosmic microwave background observatories and protostellar disk-scale interferometric observations to probe magnetic fields at the critical scales at which clouds collapse to form stars. An overview of PRIMA’s basic design and capabilities will be presented. Other posters in this session describe PRIMA science, technology, and instrumentation in greater depth.

Jason Glenn↗
NASA NTRS2021

Reconnection and particle acceleration in 3D current sheet evolution in moderately-magnetized astrophysical pair plasma

Magnetic reconnection, a plasma process converting magnetic energy to particle kinetic energy, is often invoked to explain magnetic energy releases powering high-energy flares in astrophysical sources including pulsar wind nebulae and black hole jets. Reconnection is usually seen as the (essentially 2D) nonlinear evolution of the tearing instability disrupting a thin current sheet. To test how this process operates in 3D, we conduct a comprehensive particle-in-cell simulation study comparing 2D and 3D evolution of long, thin current sheets in moderately-magnetized, collisionless, relativistically-hot electron- positron plasma, and find dramatic differences. We first systematically characterize this process in 2D, where classic, hierarchical plasmoid-chain reconnection determines energy release, and explore a wide range of initial configurations, guide magnetic field strengths, and system sizes. We then show that 3D simulations of similar configurations exhibit a diversity of behaviours, including some where energy release is determined by the nonlinear relativistic drift-kink instability. Thus, 3D current-sheet evolution is not always fundamentally classical reconnection with perturbing 3D effects, but, rather, a complex interplay of multiple linear and nonlinear instabilities whose relative importance depends sensitively on the ambient plasma, minor configuration details, and even stochastic events. It often yields slower but longer-lasting and ultimately greater magnetic energy release than in 2D. Intriguingly, nonthermal particle acceleration is astonishingly robust, depending on the upstream magnetization and guide field, but otherwise yielding similar particle energy spectra in 2D and 3D. Though the variety of underlying current-sheet behaviours is interesting, the similarities in overall energy release and particle spectra may be more remarkable.

Gregory R. Werner↗
NASA NTRSDate not supplied

ACROSS: Supporting Time Domain and Multi-Messenger Astrophysics

The Astro2020 Decadal Survey recommended an investment in Time Domain and Multi-Messenger Astrophysics (TDAMM) as the top-priority sustaining activity in space for the coming decade. One aspect of NASA’s response to this recommendation is a study, led by the Physics of the Cosmos Program Office, of how a structure akin to a General Observer Facility might be implemented that would provide support to both missions and observers as they pursue TDAMM science. Here, we present some initial observations of needs in the community, and potential concepts for such an entity. We invite discussion with both missions and observers to better understand their needs and concerns.

Brian Humensky↗
NASA NTRSDate not supplied

New Astrophysical Discovery with Ground and Space-Based Observatories

Astronomy is robust with discovery thanks to a wide range of international observing facilities in space and on the ground. For example, space telescopes such as Webb and Hubble are now detecting the most distant galaxies in the universe, as well as the cosmological effects of dark matter and dark energy. Ground based radio telescope arrays are peering into nurseries of star-formation, finding regions of infant stars and also their circumstellar disks in which planetary systems are forming. Even black holes have now been imaged. This overview talk will highlight recent advances in observational astrophysics, especially the scientifically powerful examples where multiple facilities are used in complement. Examples include the study of solar system bodies, the characterization of exoplanet atmospheres, and detections of electromagnetic radiation associated with cosmic sources of gravitational waves.

Jennifer J Wiseman↗
NASA NTRS2025

On the Stability Analysis of Astrophysical Cooling Functions

To model the temperature evolution of optically thin astrophysical environments at MHD scales, radiative and collisional cooling rates are typically either pretabulated or fit into a functional form and then input into MHD codes as a radiative loss function. Thermal balance requires estimates of the analogous heating rates, which are harder to calculate, and due to uncertainties in the underlying dissipative heating processes these rates are often simply parameterized. The resulting net cooling function defines an equilibrium curve that varies with density and temperature. Such cooling functions can make the gas prone to thermal instability (TI), which will cause departures from equilibrium. There has been no systematic study of thermally unstable parameter space for nonequilibrium states. Motivated by our recent finding that there is a related linear instability, catastrophic cooling instability, that can dominate over TI, here we carry out such a study. We show that Balbus instability criteria for TI can be used to define a critical cooling rate, Λc, that permits a nonequilibrium analysis of cooling functions through the mapping of TI zones. We furthermore illustrate how thermal conduction modifies the shape of TI zones. Upon applying a Λc-based stability analysis to coronal loop simulations, we find that loops undergoing periodic episodes of coronal rain formation are linearly unstable to catastrophic cooling instability, while TI is stabilized by thermal conduction.

Amanda Stricklan↗
DOE OSTI2024

6Li as a three-body system in the (p, 3He) reaction at astrophysical energies

Several astrophysical processes are governed by the occurrence of nuclear reactions involving light nuclei at energies below the Coulomb barrier. Among other effects, their understanding is challenged by the appearance of clustered structures in the ground-state configuration of some of these nuclei, which may have a significant impact on the reaction cross section. In this contribution, we focus on the Li 6 (p, He 3 ) He 4 reaction, to probe the role of clustered configurations of Li 6 . In particular, we consider a three-body ab-initio calculation, based on the hyperspherical harmonics (HH) method, of the Li 6 wave function (WF), together with a more phenomenological three-body model. We observe that the HH WF entails a degree of clustering much larger than obtained from the phenomenological WFs. However, the corresponding reaction cross section, evaluated as a direct two-nucleon transfer in distorted-wave Born approximation, still follows the scaling with the clustering strength already pointed out in a previous work [1] and exhibits an energy trend very similar to that obtained with realistic phenomenological WFs. This opens up interesting perspectives towards constraining

Perrotta, S.↗
DOE OSTI2026

Astrophysical Neutrino Sources as Colliders

High-energy neutrinos arise from processes at large center-of-mass energies, offering a window to test physics at comparable scales or beyond those accessible in collider experiments on Earth. Here, we present a recipe for extracting two-sided bounds on the inelastic $pp$ and $pγ$ cross sections from neutrino point-source data, by independently constraining every astrophysical input (cosmic-ray luminosities and target densities) through electromagnetic observations or theoretical arguments. The cross section is then the only remaining free parameter. Applying this framework to the IceCube associations with TXS~0506+056, NGC~1068, and the Galactic Plane, to a stacked population of eleven X-ray bright Seyfert galaxies, to the ultra-high-energy KM3NeT event KM3-230213A, and to projected observations of ultra-high-energy neutrinos, we obtain constraints that span center-of-mass energies from $\sqrt{s}\sim 1$ GeV to $\sim 10^{5}$ GeV, some of which are well beyond the reach of the LHC and, for the $pγ$ channel, beyond HERA. Several of these bounds are more stringent than unitarity limits.

Argüelles, Carlos A. [Harvard U.]↗
DOE OSTI2026

Looking for New Particle Physics with Astrophysical Origin

In this thesis, I explore the consequences of introducing new particles into astrophysical environments, and place constraints on these particles using available data. I first consider Heavy Neutral Leptons (a proposed particle which has important implications for neutrinos) in the context of atmospheric interactions, the Sun, and supernovae. I then turn my focus to various models of dark matter, considering the reach of both the terrestrial and astronomical observables. A special focus is given to cases where dark matter clusters around Supermassive Black Holes.

Gustafson, Robert Andrew [Virginia Tech., Blacksbu↗
DOE OSTI2024

Skeletal Kinetics Reduction for Astrophysical Reaction Networks

A novel methodology is developed to extract accurate skeletal reaction models for nuclear combustion. Local sensitivities of isotope mass fractions with respect to reaction rates are modeled based on the forced optimally time-dependent (f-OTD) scheme. These sensitivities are then analyzed temporally to generate skeletal models. The methodology is demonstrated by conducting skeletal reduction of constant density and temperature burning of carbon and oxygen relevant to Type Ia supernovae (SNe Ia). The 495-isotopes Torch model is chosen as the detailed reaction network. A map of maximum production of 56 Ni in SNe Ia is produced for different temperatures, densities, and proton-to-neutron ratios. The f-OTD simulations and the sensitivity analyses are then performed with initial conditions from this map. A series of skeletal models are derived and their performances are assessed by comparison against currently existing skeletal models. Previous models have been constructed intuitively by assuming the dominance of α-chain reactions. The comparison of the newly generated skeletal models against previous models is based on the predicted energy release and 44 Ti and 56 Ni abundances by each model. The consequences of ye ≠ 0.5 in the initial composition are also explored where ye is the electron fraction. The simulated results show that 56 Ni production decreases by decreasing ye as expected, and that the 43 Sc is a key isotope in proton and neutron channels toward 56 Ni production. It is shown that an f-OTD skeletal model with 150 isotopes can accurately predict the 56Ni abundance in SNe Ia for ye ≲ 0.5 initial conditions.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2013

Mach stem hysteresis: Experiments addressing a novel explanation of clumpy astrophysical jet emission

Recent time-series observations of shock waves in stellar jets taken with the Hubble Space Telescope reveal localized bright knots that persist over nearly 15 years. While some of these features represent shock fronts caused by variable velocities in the flow, others appear at the intersection points between distinct bow shocks. Theoretically, when the angle between two intersecting shocks exceeds a certain critical value, a third shock (Mach stem) should form. Because Mach stems form perpendicular to the direction of flow, incoming particles encounter a normal shock instead of an oblique one, which results in brighter emission at this location. In order to study this phenomenon in a controlled laboratory setting, we have carried out experiments on the Omega laser aimed at understanding the formation, growth, and destruction of Mach stems in the warm dense plasma regime. Our experimental results indicate how the growth rate depends upon included angle, and numerical simulations indicate that it may be possible to stabilize an already-formed Mach stem below the critical angle when certain conditions are satisfied.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗