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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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All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Energetic electrons in impulsive and extended solar flares as deduced from flux correlations between hard X-rays and microwaves

The peak flux relationship between hard X-rays and microwaves from solar flares is studied using about 400 events simultaneously recorded with the hard X-ray burst spectrometer on the SMM satellite and the Nobeyama 17 GHz radiometer. The data indicate that the hard X-ray and microwave peak fluxes correlate best for X-ray energies of less than about 80 keV for impulsive flares and greater than about 360 keV for extended flares. By postulating that electrons responsible for microwave emission at 17 GHz are those emitting hard X-rays at these photon energies, it is concluded that: (1) in impulsive flares, microwaves at about 20 GHz are emitted mainly by electrons of less than about 200 keV from a layer through which the electrons stream down into the thick-target hard X-ray source; and (2) in extended flares, microwaves are emitted mainly by MeV electrons trapped in a coronal loop or loops.

Kosugi, Takeo↗
NASA NTRS1990

Statistical study of the correlation of hard X-ray and type III radio bursts in solar flares

A large number of hard X-ray events which occurred during the maximum of solar cycle 21 have been analyzed in order to study their correlation with type III bursts. It is found that the distribution of occurrences of hard X-ray bursts correlated with type III radio bursts is significantly different from the distribution of all hard X-ray bursts. This result is consistent with the assumption that the hard X-ray and type III intensities are somewhat correlated. A bivariate distribution function of the burst intensities is fitted to the data and is used to determine that the typical ratio of X-ray intensity to type II intensity is about 10 and that the ratio of the number of X-ray producing-electrons to type III-producing electrons is about 1000. Three models which have been proposed to explain the relation between the accelerated hard X-ray and type III-producing electrons are examined in the context of these observations.

Hamilton, Russell J.↗
NASA NTRS1991

The association of solar millisecond radio spikes with hard X-ray emission

Conventional observational data regarding solar millisecond spikes are compared with data gathered simultaneously in the hard X-ray band by means of a statistical analysis. The analysis considers the association rate, correlation degree, and relative time delays between hard X-ray emissions (in the 25-438 keV range) and radio-spike events. About 95 percent of the radio-spike bursts occur during impulsive hard X-ray bursts, and approximately 43 percent of the compared events are characterized by hard X-ray time profiles that mimic the concentration of simultaneous radio spikes. The delay of the radio emission with respect to the hard X-ray bursts puts some constraints on the acceleration and propagation of particles. The time delays and the quantization into discrete radio events are theorized to be caused by the operation of the accelerator.

Guedel, M.↗
NASA NTRS1992

Stereoscopic observations of a solar flare hard X-ray source in the high corona

The vertical structure of the impulsive and gradual hard X-ray sources in high coronae and the characteristics of the impulsive soft X-ray emission are investigated on the basis of PVE, ICE, and GOES observations of the energetic flare on February 16, 1984. The average photon spectra observed by these instruments during the impulsive and gradual hard X-ray bursts are summarized. A comparison of these unocculted and partially occulted spectra shows that the sources of the impulsive hard X-ray (greater than about 25 keV) and impulsive soft X-ray (2-5 keV) emissions in this flare extended to coronal altitudes greater than about 200,000 km above the photosphere. At about 100 keV, the ratio of the coronal source brightness to the total source brightness was 0.001 during the impulsive phase and less than about 0.01 during the gradual hard X-ray burst. The sources of the gradual hard X-ray burst and gradual soft X-ray burst were almost completely occulted, indicating that these sources were located at heights less than 200,000 km above the photosphere.

Kane, S. R.↗
NASA NTRS1992

Imaging solar flares in hard X-rays using Fourier telescopes

The sun emits hard X-rays (above 10 keV) during solar flares. Imaging hard X-ray sources on the sun with spatial resolutions on the order of 1-5 arcsec and integration times of 1 sec will provide greater insight into the energy release processes during a solar flare. In these events, tremendous amounts of energy stored in the solar magnetic field are rapidly released leading to emission across the electromagnetic spectrum. Two Fourier telescope designs, a spatial modulation collimator and a rotating modulation collimator, were developed to image the full sun in hard X-rays (10-100 keV) in an end-to-end simulation. Emission profiles were derived for two hard X-ray solar flare models taken from the current solar theoretical literature and used as brightness distributions for the telescope simulations. Both our telescope models, tailored to image solar sources, were found to perform equally well, thus offering the designer significant flexibility in developing systems for space-based platforms. Given sufficient sensitive areas, Fourier telescopes are promising concepts for imaging solar hard X-rays.

Campbell, Jonathan W.↗
NASA NTRS1994

The correlation of solar flare hard X-ray bursts with Doppler blueshifted soft X-ray flare emission

We have investigated the temporal correlation between hard X-ray bursts and the intensity of Doppler blueshifted soft X-ray spectral line emission. We find a strong correlation for many events that have intense blueshifted spectral signatures and some correlation in events with modest blueshifts. The onset of hard X-rays frequently coincides to within a few seconds with the onset of blueshifted emission. The peak intensity of blueshifted emission is frequently close in time to the peak of the hard X-ray emission. Decay rates of the blueshifted and hard X-ray emission are similar, with the decay of the blueshifted emission tending to lag behind the hard X-ray emission in some cases. There are, however, exceptions to these conclusions, and, therefore, the results should not be generalized to all flares. Most of the data for this work were obtained from instruments flown on the Japanese Yohkoh solar spacecraft.

Bentley, R. D.↗
NASA NTRS1998

Discovery of Correlated Behavior Between the Hard X-Ray and the Radio Bands in Cygnus X-3

Using CGRO/BATSE hard X-ray data and GHz radio monitoring data from the Green Bank Interferometer (GBI), we have performed a long term study (approximately 1800 days) of the unusual X-ray binary Cygnus X-3 resulting in the discovery of a remarkable relationship between the two wavelength bands. We find that quiescent radio states are strongly anticorrelated with the intensity of the hard X-ray emission. With the onset of a flaring state the relationship switches to a correlation. This is most easily seen in the larger (> or = 1 Jy) flares where the preflare quenched radio emission is accompanied by a very low hard X-ray intensity, and recovery of the hard X-ray flux during the radio flare. The injection of plasma into the radio jets, associated with Cyg X-3, can be directly related to changes in the hard X-ray emission, and suggests the possibility of accretion-related and jet-related components of the high energy emission.

McCollough, M. L.↗
NASA NTRS2002

Hard X-Ray Emission of X-Ray Bursters

The primary goal of this proposal was to increase our understanding of the accretion dynamics and emission mechanisms in neutron-star low-mass x-ray binaries via accurate measurements of their broad-band x-ray spectrum with particular emphasis on the hard x-ray emission. We obtained an extensive set of Rossi X-Ray Timing Explorer (RXTE) observations of a bright hard x-ray outburst from the source 4U1728-34 including data obtained under this proposal and previously scheduled observations for another observer. We have constructed x-ray light curves in several energy bands, including hard energy bands, from these data. We also completed spectral analysis of several observations which show strong hard x-ray emission. We are currently performing timing analysis to search for possible correlations between the spectral and timing evolution of 4U1728-34. Due to the one-year delay in obtaining the observations made for the other observer (which are the ones containing the peak of the hard X-ray emission), the analysis for this project is not yet complete. Because 4U1728-34 shows interesting high-frequency timing behavior, we plan to complete the analysis as part of our on-going investigation of high-frequency timing of X-ray binaries.

Kaaret, P.↗
NASA NTRS2003

Non-Thermal Hard X-Ray Emission in Galaxy Clusters Observed with the BeppoSAX PDS

We study the X-ray emission in a Sample of galaxy clusters using the BeppoSAX PDS instrument in the 20 - 80 keV energy band. We estimate the non-thermal hard X-ray cluster emission (HXR) by modeling the thermal contribution from the cluster gas and the non-thermal contamination from the unobscured AGN in the clusters. We also evaluate the systematic uncertainties due to the background fluctuations. Assuming negligible contamination from the obscured AGN, the resulting non-thermal component is detected at a 2 sigma level in approx. 50% of the non-significantly AGN-contaminated clusters: A2142, A2199, A2256, A3376, Coma, Ophiuchus and Virgo. The data are consistent with a scenario whereby relaxed clusters have no hard X-ray component of non-thermal origin, whereas merger clusters do. The co-added spectrum of the above clusters indicates a power-law spectrum for the HXR with a photon index of 2.8+0.3-0.4 in the 12 - 115 keV band, and we find indication that it has extended distribution. These indications argue against significant contamination from obscured AGN, which have harder spectra and centrally concentrated distribution. These results are supportive of the assumption of the merger shock acceleration of electrons in clusters, which has been proposed as a possible origin of the non-thermal hard X-ray emission models. Assuming that the Cosmic Microwave Background photons experience Inverse Compton scattering from the merger-accelerated relativistic electrons, and thus produce the observed HXR, the measured hard X-ray slope corresponds to a differential momentum spectra of the relativistic electrons with a slope of mu = 3.8 - 5.0. In presence of cluster magnetic fields this relativistic electron population produces synchrotron emission with a spectral index of 1.4 - 2.1, consistent with radio halo observations of merger clusters. Thus both hard X-ray and radio observations of merger clusters are consistent with the Inverse Compton model. The observed slope of HXR is also consistent with that predicted by the non-thermal bremsstrahlung, which chus cannot be ruled by the fit to the current data, even though this model requires an extreme, untenable cluster energetics. Assuming centrally concentrated distribution of HXR, the data requires a harder slope for the HXR spectrum, which is consistent with secondary electron models, but this model yields a worse fit to the PDS data and thus seems to be disfavored over the primary electron Inverse Compton model.

Nevalainen, J.↗
NASA NTRS2004

Non-Thermal Hard X-Ray Emission in Galaxy Clusters Observed with the BeppoSAX PDS

We study the X-ray emission in a sample of galaxy clusters using the BeppoSAX PDS instrument in the 20-80 keV energy band. We estimate the nonthermal hard X-ray (HXR) cluster emission by modeling the thermal contribution from the cluster gas and the nonthermal contamination from the unobscured active galactic nuclei (AGNs) in the clusters. We also evaluate the systematic uncertainties due to the background fluctuations. Assuming negligible contamination from the obscured AGNs, the resulting nonthermal component is detected at a 2 sigma level in approx. 50% of the nonsignificantly AGN-contaminated clusters: A2142, A2199, A2256, A3376, Coma, Ophiuchus, and Virgo. The data are consistent with a scenario whereby relaxed clusters have no hard X-ray component of nonthermal origin, whereas merger clusters do, with a 20-80 keV luminosity of approx. 10(exp 43)-10(exp 44) h(sup -2 sub 50) ergs/s. The co-added spectrum of the above clusters indicates a power-law spectrum for the HXR emission with a photon index of 2.8(sup +0.3 sub -0.4) in the 12-115 keV band, and we find indication that it has extended distribution. These indications argue against significant contamination from obscured AGNs, which have harder spectra and a centrally concentrated distribution. These results are supportive of the assumption of the merger shock acceleration of electrons in clusters, which has been proposed as a possible origin of the nonthermal hard X-ray emission models. Assuming that the cosmic microwave background photons experience inverse Compton scattering from the merger-accelerated relativistic electrons and thus produce the observed HXR, the measured hard X-ray slope corresponds to a differential momentum spectra of the relativistic electrons with a slope of mu = 3.8-5.0. In presence of cluster magnetic fields this relativistic electron population produces synchrotron emission with a spectral index of 1.4-2.1, consistent with radio halo observations of merger clusters. Thus both hard X-ray and radio observations of merger clusters are consistent with the inverse Compton model.

Nevalainen, J.↗
NASA NTRS2010

Galactic Black Holes in the Hard State: A Multi-Wavelength View of Accretion and Ejection

The canonical hard state is associated with emission from all three fundamental accretion components: the accretion disk, the hot accretion disk corona and the jet. On top of these, the hard state also hosts very rich temporal variability properties (low frequency QPOs in the PDS, time lags, long time scale evolution). Our group has been working on the major questions of the hard state both observationally (with mult i-wavelength campaigns using RXTE, Swift, Suzaku, Spitzer, VLA, ATCA, SMARTS) and theoretically (through jet models that can fit entire SEDs). Through spectral and temporal analysis we seek to determine the geometry of accretion components, and relate the geometry to the formation and emission from a jet. In this presentation I will review the recent contributions of our group to the field, including the Swift results on the disk geometry at low accretion rates, the jet model fits to the hard state SEDs (including Spitzer data) of GRO J1655-40, and the final results on the evolution of spectral (including X-ray, radio and infrared) and temporal properties of elected black holes in the hard states. I will also talk about impact of ASTROSAT to the science objective of our group.

Kalemci↗
NASA NTRS2011

Fault-Tolerant, Radiation-Hard DSP

Commercial digital signal processors (DSPs) for use in high-speed satellite computers are challenged by the damaging effects of space radiation, mainly single event upsets (SEUs) and single event functional interrupts (SEFIs). Innovations have been developed for mitigating the effects of SEUs and SEFIs, enabling the use of very-highspeed commercial DSPs with improved SEU tolerances. Time-triple modular redundancy (TTMR) is a method of applying traditional triple modular redundancy on a single processor, exploiting the VLIW (very long instruction word) class of parallel processors. TTMR improves SEU rates substantially. SEFIs are solved by a SEFI-hardened core circuit, external to the microprocessor. It monitors the health of the processor, and if a SEFI occurs, forces the processor to return to performance through a series of escalating events. TTMR and hardened-core solutions were developed for both DSPs and reconfigurable field-programmable gate arrays (FPGAs). This includes advancement of TTMR algorithms for DSPs and reconfigurable FPGAs, plus a rad-hard, hardened-core integrated circuit that services both the DSP and FPGA. Additionally, a combined DSP and FPGA board architecture was fully developed into a rad-hard engineering product. This technology enables use of commercial off-the-shelf (COTS) DSPs in computers for satellite and other space applications, allowing rapid deployment at a much lower cost. Traditional rad-hard space computers are very expensive and typically have long lead times. These computers are either based on traditional rad-hard processors, which have extremely low computational performance, or triple modular redundant (TMR) FPGA arrays, which suffer from power and complexity issues. Even more frustrating is that the TMR arrays of FPGAs require a fixed, external rad-hard voting element, thereby causing them to lose much of their reconfiguration capability and in some cases significant speed reduction. The benefits of COTS high-performance signal processing include significant increase in onboard science data processing, enabling orders of magnitude reduction in required communication bandwidth for science data return, orders of magnitude improvement in onboard mission planning and critical decision making, and the ability to rapidly respond to changing mission environments, thus enabling opportunistic science and orders of magnitude reduction in the cost of mission operations through reduction of required staff. Additional benefits of COTS-based, high-performance signal processing include the ability to leverage considerable commercial and academic investments in advanced computing tools, techniques, and infra structure, and the familiarity of the science and IT community with these computing environments.

Czajkowski, David↗
NASA NTRS2019

Detection of Nonthermal Hard X-Ray Emission from the “Fermi Bubble” in an External Galaxy

We report new Chandra hard X-ray (>2 keV) and Jansky Very Large Array C-band observations of the nuclear super bubble of NGC 3079, an analog of the “Fermi bubble” in our Milky Way. We detect extended hard X-ray emission on the southwest (SW)side of the galactic nucleus with coherent multiwavelength features in radio, Hα, and soft X-ray. The hard X-ray feature has a cone shape with possibly a weak cap, forming a bubble-like structure with a diameter of∼1.1 kpc. A similar extended feature, however, is not detected on the northeast (NE)side, which is brighter in all other wavelengths such as radio, Hα, and soft X-ray. Scattered photons from the nuclear region or other nearby point-like X-ray bright sources, inverse Compton emission from cosmic-ray(CR)electrons via interaction with the cosmic microwave background, or any individually faint stellar X-ray source populations, cannot explain the extended hard X-ray emission on the SW side and the strongly NE/SW asymmetry. A synchrotron emission model, plus a thermal component accounting for the excess at∼1 keV, can well characterize the broadband radio/hard X-ray spectra. The broadband synchrotron spectra do not show any significant cutoff, and even possibly slightly flatten at higher energy. This rule out a loss-limited scenario in the acceleration of the CR electrons in or around this superbubble. As the first detection of kiloparsec-scale extended hard X-ray emission associated with a galactic nuclear superbubble, the spatial and spectral properties of the multiwavelength emissions indicate that the CR leptons responsible for the broadband synchrotron emission from the SW bubble must be accelerated in situ, instead of transported from the nuclear region of the galaxy.

Jiang-Tao Li↗
NASA NTRS2016

Performance of ASTRO-H Hard X-Ray Telescope (HXT)

The Japanese X-ray Astronomy Satellite, Hitomi (ASTRO-H) carries hard X-ray imaging system, covering the energy band from 5 keV to 80 keV. The hard X-ray imaging system consists of two hard X-ray telescopes (HXT) and two hard X-ray imagers (HXI). The HXT employs tightly-nested, conically-approximated thin foil Wolter-I optics. The mirror surfaces of HXT were coated with PtC depth-graded multilayers. We carried out ground calibrations of HXTs at the synchrotron radiation facility SPring-8 BL20B2 in Japan, and found that total effective area of two HXTs was about 350 sq cm at 30 keV, and the half power diameter of HXT was about 1.9. After the launch of Hitomi, Hitomi observed several targets during the initial functional verification of the onboard instruments. The Hitomi software and calibration team (SCT) provided the Hitomis data of G21.5-0.9, a pulsar wind nebula, to the hardware team for the purpose of the instrument calibration. Through the analysis of the in-flight data, we have confirmed that the X-ray performance of HXTs in orbit was consistent with that estimated by the ground calibrations.

hard X-ray telescope↗
NASA NTRS1930

The relation between the tensile strength and the hardness of metals

This report presents methods determining the hardness and tensile strength of metals by showing the effect and dependence of the hardness numbers on the strain-hardening. Relations between the hardness numbers and the ordinary stress-strain diagrams and tensile strength are given. Procedures for finding the Brinell strength are also presented.

METALS - NICKEL HARDNESS TESTS↗
DOE OSTI2026

Optimization of Processing, Microstructure, and Hardness of an Al–Ce–Ni–Mn–Zr Alloy With Laser Additive Manufacturing

Here, this study examines the processing behavior, microstructure, surface roughness, and hardness properties of an aluminum alloy containing 8.2 Ce, 4.5 Ni, 0.5 Mn, and 0.7 Zr (wt%) fabricated using laser powder bed fusion. Sixty samples were produced across a range of laser powers, scan speeds, and hatch spacings to evaluate their effect on porosity, hardness, and microstructural features. Porosity was measured using X-ray computed tomography, while microstructure and surface roughness were characterized by scanning electron (SEM) and laser confocal microscopy. High dense and cracking-free Al–Ni–Ce alloy was successfully manufactured. Porosity showed a U-shaped dependence on energy input, increasing under both insufficient and excessive melting conditions. Hardness increased with cooling rate due to finer cellular structures and solute redistribution. A general statistical model was developed to capture the relationships between processing parameters and material response. Results identify a narrow processing window defined by laser powers between 350 and 370 W, scan speeds from 1400 to 1800 mm/s, and hatch distances between 0.14 and 0.18 mm. Within this window, porosity is minimized (below 0.01%) and hardness is maximized (up to 160 HV), demonstrating that careful control of these parameters enables dense, high strength aluminum components suitable for demanding structural applications.

Aluminum alloys↗
NASA NTRS2013

Long-Term Variability of AGN at Hard X-Rays

Variability at all observed wavelengths is a distinctive property of active galactic nuclei (AGN). Hard X-rays provide us with a view of the innermost regions of AGN, mostly unbiased by absorption along the line of sight. Characterizing the intrinsic hard X-ray variability of a large AGN sample and comparing it to the results obtained at lower X-ray energies can significantly contribute to our understanding of the mechanisms underlying the high-energy radiation. Methods. Swift/BAT provides us with the unique opportunity to follow, on time scales of days to years and with a regular sampling, the 14-195 keV emission of the largest AGN sample available up to date for this kind of investigation. As a continuation of an early work on the first 9 months of BAT data, we study the amplitude of the variations, and their dependence on sub-class and on energy, for a sample of 110 radio quiet and radio loud AGN selected from the BAT 58-month survey. About 80 of the AGN in the sample are found to exhibit significant variability on months to years time scales, radio loud sources being the most variable. The amplitude of the variations and their energy dependence are incompatible with variability being driven at hard X-rays by changes of the absorption column density. In general, the variations in the 14-24 and 35-100 keV bands are well correlated, suggesting a common origin of the variability across the BAT energy band. However, radio quiet AGN display on average 10 larger variations at 14-24 keV than at 35-100 keV and a softer-when-brighter behavior for most of the Seyfert galaxies with detectable spectral variability on month time scale. In addition, sources with harder spectra are found to be more variable than softer ones. These properties are generally consistent with a variable power law continuum, in flux and shape, pivoting at energies 50 keV, to which a constant reflection component is superposed. When the same time scales are considered, the timing properties of AGN at hard X-rays are comparable to those at lower energies, with at least some of the differences possibly ascribable to components contributing differently in the two energy domains (e.g., reflection, absorption).

X-rays↗
NASA NTRS2016

Hardness and Microstructure of Binary and Ternary Nitinol Compounds

The hardness and microstructure of twenty-six binary and ternary Nitinol (nickel titanium, nickel titanium hafnium, nickel titanium zirconium and nickel titanium tantalum) compounds were studied. A small (50g) ingot of each compound was produced by vacuum arc remelting. Each ingot was homogenized in vacuum for 48 hr followed by furnace cooling. Specimens from the ingots were then heat treated at 800, 900, 1000 or 1100 degree C for 2 hr followed by water quenching. The hardness and microstructure of each specimen was compared to the baseline material (55-Nitinol, 55 at.% nickel - 45 at.% titanium, after heat treatment at 900 degC). The results show that eleven of the studied compounds had higher hardness values than the baseline material. Moreover, twelve of the studied compounds had measured hardness values greater 600HV at heat treatments from 800 to 900 degree C.

intermetallics↗