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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 595 records · Page 33
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

A 21 micron emission feature in four proto-planetary nebulae

The discovery of an unidentified emission feature at 21 microns in the LRS spectra of four IRAS sources is reported. These objects all show large FIR excesses due to a circumstellar dust envelope surrounding a carbon-rich central star and are likely to be in the evolutionary phase between the asymptotic giant branch and planetary nebula stages. The strength of the feature and the carbon richness of the objects suggest that this feature is due to the bending mode of a transient carbon-bearing molecule.

Kwok, Sun↗
NASA NTRS1998

Very Rapid Phenomena in Sco X-1

With the launch of the Rossi X-ray Timing Explorer the high-frequency part of the power density spectra became for the first time accessible to astronomers. The main result of the project supported by grant NAG5-3271 is our discovery of quasi-periodic oscillations (QPOs) in the kiloHertz range for Sco X-1. This discovery has been followed by detections of kHz QPOs in numerous other X-ray binary sources. This has been one of the most fruitful areas of research for the Rossi XTE. The physical interpretation of these QPOs is, as yet, unclear.

VanParadijs, Johannes A.↗
NASA NTRS2005

Correlations of (Delta)O-17 with Chemical Characteristics Among Chondrite Groups

Demonstration of mass-independent O isotopic variations in solar system materials was a seminal discovery of meteoritics. These variations were thought to reflect incomplete mixing of O from different nucleosynthesis sources. Since then, two non-nucleosynthetic causes have been suggested: (1) differential photodissociation of distinct isotopomers of CO, enriching nebular gas in chemically reactive heavy O, and (2) gas-phase molecular reactions producing mass-independent O isotopic exchange. Nebular processes caused chemical fractionations that are observed in chondrite bulk compositions. If nebular processes also produced mass-independent O isotopic variations, then these may correlate with chondrite bulk chemistry.

Mittlefehldt, D. W.↗
NASA NTRS2010

Origin of the Central Constant Emission Component of Eta Carinae

The X-ray campaign observation of the wind-wind colliding (WWC) binary system, Eta Carinae, targeted at its periastron passage in 2003, presented a detailed view of the flux and spectral variations of the X-ray minimum phase. One of the discoveries in this campaign was a central constant emission (CCE) component very near the central WWC source (Hamaguchi et al. 2007, ApJ, 663, 522). The CCE component was noticed between 1-3 keY during the X-ray minima and showed no variation on either short timescales within any observation or long timescales of up to ~ 10 years. Hamaguchi et al. (2007) discussed possible origins as collisionally heated shocks from the fast polar winds from Eta Car or the fast moving outflow from the WWC with the ambient gas, or shocked gas that is intrinsic to the wind of Eta Car. During the 2009 periastron passage, we launched another focussed observing campaign of Eta Carinae with the Chandra, XMM-Newton and Suzaku observatories, concentrating on the X-ray faintest phase named the deep X-ray minimum. Thanks to multiple observations during the deep X-ray minimum, we found that the CCE spectrum extended up to 10 keV, indicating presence of hot plasma of kT approx.4-6 keV. This result excludes two possible origins that assume relatively slow winds (v approx. 1000 km/s) and only leaves the possibility that the CCE plasma is wind blown bubble at the WWC downstream. The CCE spectrum in 2009 showed a factor of 2 higher soft band flux as the CCE spectrum in 2003, while the hard band flux was almost unchanged. This variation suggests decrease in absorption column along the line of sight. We compare this result with recent increase in V-band magnitude of Eta Carinae and discuss location of the CCE plasma.

Hamaguchi, Kenji↗
NASA NTRS2013

An Evolving Compact Jet in the Black Hole X-Ray Binary Maxi J1836-194

We report striking changes in the broadband spectrum of the compact jet of the black hole transient MAXI J1836−194 over state transitions during its discovery outburst in 2011. A fading of the optical-infrared (IR) flux occurred as the source entered the hard-intermediate state, followed by a brightening as it returned to the hard state. The optical-IR spectrum was consistent with a power law from optically thin synchrotron emission, except when the X-ray spectrum was softest. By fitting the radio to optical spectra with a broken power law, we constrain the frequency and flux of the optically thick/thin break in the jet synchrotron spectrum. The break gradually shifted to higher frequencies as the source hardened at X-ray energies, from approx 10(exp 11) to approx 4 × 10(exp 13) Hz. The radiative jet luminosity integrated over the spectrum appeared to be greatest when the source entered the hard state during the outburst decay (although this is dependent on the high-energy cooling break, which is not seen directly), even though the radio flux was fading at the time. The physical process responsible for suppressing and reactivating the jet (neither of which are instantaneous but occur on timescales of weeks) is uncertain, but could arise from the varying inner accretion disk radius regulating the fraction of accreting matter that is channeled into the jet. This provides an unprecedented insight into the connection between inflow and outflow, and has implications for the conditions required for jets to be produced, and hence their launching process.

binary↗
NASA NTRS1980

Discovery of low-redshift X-ray selected quasars - New clues to the QSO phenomenon

The identification of six X-ray sources discovered by the Einstein Observatory with X-ray quasars is reported, and the properties of these X-ray selected quasars are discussed. The four high-latitude fields of 1 sq deg each in which the Einstein imaging proportional counter detected serendipitous X-ray sources at intermediate exposures of 10,000 sec were observed by 4-m and 1.5-m telescopes, and optical sources with uv excesses and emission line spectra typical of many low-redshift quasars and Seyfert 1 galaxies were found within the 1-arcsec error boxes of the X-ray sources. All six quasars identified were found to be radio quiet, with low redshift and relatively faint optical magnitudes, and to be similar in space density, colors and magnitude versus redshift relation to an optically selected sample at the same mean magnitude. X-ray luminosity was found to be well correlated with both continuum and broad-line emission luminosities for the known radio-quiet quasars and Seyfert 1 galaxies, and it was observed that the five objects with the lowest redshifts have very similar X-ray/optical luminosity ratios despite tenfold variations in X-ray luminosity. It is concluded that photoionization by a continuum extending to X-ray energies is the dominant excitation mechanism in radio-quiet quasars.

Grindlay, J. E.↗
DOE OSTI2020

Provenance infrastructure for multimodal x-ray experiments and reproducible analysis

Exploring relationships between material structures and desired properties for material discovery and synthesis requires mining machine-readable databases and linking experimental data with sufficiently rich annotations. There are vast gaps both in these data sources and in the connections between them. We present a provenance-based data management and analysis framework that enables capturing, persisting, and reanalyzing experimental data from the BNL National Synchrotron Light Source II (NSLS-II). Our system leverages NSLS-II Bluesky for experimental data acquisition, captures analysis parameters, and enriches the search space with results from the scientific literature. We describe in detail the challenges and benefits of data-driven approaches when comparing computational and experimental data, such as the multiple possible scenarios of interest in often ill-posed inverse problems and missing data. Our infrastructure utilizes the NSLS-II event model and includes discovery mechanisms across multiple beamlines. A text and data mining module using natural language processing classification techniques extracts relevant information from the literature that is added to data sources. We describe a provenance acquisition and analysis rerun workflow based on a directed acyclic graph that keeps track of process and data provenance and allows to replay analysis.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS2014

NuSTAR J163433-4738.7: A Fast X-Ray Transient in the Galactic Plane

During hard X-ray observations of the Norma spiral arm region by the Nuclear Spectroscopic Telescope Array (NuSTAR) in 2013 February, a new transient source, NuSTAR J163433-4738.7, was detected at a significance level of 8sigma in the 3-10 keV bandpass. The source is consistent with having a constant NuSTAR count rate over a period of 40 ks and is also detected simultaneously by Swift at lower significance. The source is not significantly detected by NuSTAR, Swift, or Chandra in the days before or weeks after the discovery of the transient, indicating that the strong X-ray activity lasted between approx. 0.5 and 1.5 days. Near-infrared imaging observations were carried out before and after the X-ray activity, but we are not able to identify the counterpart. The combined NuSTAR and Swift energy spectrum is consistent with a power law with a photon index of Gamma = 4.1(+1.5/−1.0) (90% confidence errors), a blackbody with kT = 1.2+/-0.3 keV, or a Bremsstrahlung model with kT = 3.0(+2.1/−1.2) keV. The reduced-χ2 values for the three models are not significantly different, ranging from 1.23 to 1.44 for 8 degrees of freedom. The spectrum is strongly absorbed with NH = (2.8(+2.3/−1.4) × 10(exp23) cm(exp−2), (9(+15 /−7) ) × 10(exp22) cm(exp−2), and (1.7(+1.7/−0.9)) × 10(exp23) cm(exp−2), for the power-law, blackbody, and Bremsstrahlung models, respectively. Although the high column density could be due to material local to the source, it is consistent with absorption from interstellar material along the line of sight at a distance of 11 kpc, which would indicate an X-ray luminosity greater than 10(exp34) erg s(exp−1). Although we do not reach a definitive determination of the nature of NuSTAR J163433-4738.7, we suggest that it may be an unusually bright active binary or a magnetar.

Near-infrared imaging observations↗
DOE OSTI2014

NuSTAR J163433-4738.7: A fast X-ray transient in the galactic plane

During hard X-ray observations of the Norma spiral arm region by the Nuclear Spectroscopic Telescope Array (NuSTAR) in 2013 February, a new transient source, NuSTAR J163433-4738.7, was detected at a significance level of 8σ in the 3-10 keV bandpass. The source is consistent with having a constant NuSTAR count rate over a period of 40 ks and is also detected simultaneously by Swift at lower significance. The source is not significantly detected by NuSTAR, Swift, or Chandra in the days before or weeks after the discovery of the transient, indicating that the strong X-ray activity lasted between ∼0.5 and 1.5 days. Near-infrared imaging observations were carried out before and after the X-ray activity, but we are not able to identify the counterpart. The combined NuSTAR and Swift energy spectrum is consistent with a power law with a photon index of Γ=4.1{sub −1.0}{sup +1.5} (90% confidence errors), a blackbody with kT = 1.2 ± 0.3 keV, or a Bremsstrahlung model with kT=3.0{sub −1.2}{sup +2.1} keV. The reduced-χ{sup 2} values for the three models are not significantly different, ranging from 1.23 to 1.44 for 8 degrees of freedom. The spectrum is strongly absorbed with N{sub H}=(2.8{sub −1.4}{sup +2.3})×10{sup 23} cm{sup –2}, (9{sub −7}{sup +15})×10{sup 22} cm{sup –2}, and (1.7{sub −0.9}{sup +1.7})×10{sup 23} cm{sup –2}, for the power-law, blackbody, and Bremsstrahlung models, respectively. Although the high column density could be due to material local to the source, it is consistent with absorption from interstellar material along the line of sight at a distance of 11 kpc, which would indicate an X-ray luminosity >10{sup 34} erg s{sup –1}. Although we do not reach a definitive determination of the nature of NuSTAR J163433-4738.7, we suggest that it may be an unusually bright active binary or a magnetar.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2016

National Synchrotron Light Source II

NSLS-II is a synchrotron light source helping researchers explore solutions to the grand energy challenges faced by the nation, and open up new regimes of scientific discovery that will pave the way to discoveries in physics, chemistry, and biology — advances that will ultimately enhance national security and help drive the development of abundant, safe, and clean energy technologies.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1978

Positions of galactic X-ray sources - At longitudes /l-II/ of 55-320 deg

Rotating modulation collimeter detectors on the SAS-3 X-ray observatory were used to supply precise (20-40 sec) positional data on 10 galactic X-ray sources in the l super II region between 55 and 320 deg. It is noted that the position for 2S0114+650 has led to the discovery of an optical counterpart. Attention is given to the temperature dependence of the experiments, and it is found that position measurements made at low temperatures are consistent with those obtained at normal (0 C) temperatures. Positions, error radii, and intensities (2-11 keV) are listed for each of the ten sources.

Dower, R. G.↗
DOE OSTI2017

Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A

We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of <0.5 mJy in 1989 to 4 mJy in 2016 ( ν = 8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in Very Long Baseline Array observations down to a scale of 4 pc, and it is coincident with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, though an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 10{sup 7} years.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2017

VLA Radio Observations of the HST Frontier Fields Cluster Abell 2744: The Discovery of New Radio Relics

Cluster mergers leave distinct signatures in the intracluster medium (ICM) in the form of shocks and diffuse cluster radio sources that provide evidence for the acceleration of relativistic particles. However, the physics of particle acceleration in the ICM is still not fully understood. Here we present new 1–4 GHz Jansky Very Large Array (VLA) and archival Chandra observations of the HST Frontier Fields Cluster Abell 2744. In our new VLA images, we detect the previously known ∼2.1 Mpc radio halo and ∼1.5 Mpc radio relic. We carry out a radio spectral analysis from which we determine the relic’s injection spectral index to be α{sub inj}=−1.12±0.19. This corresponds to a shock Mach number of M=2.05{sub −0.19}{sup +0.31} under the assumption of diffusive shock acceleration. We also find evidence for spectral steepening in the post-shock region. We do not find evidence for a significant correlation between the radio halo’s spectral index and ICM temperature. In addition, we observe three new polarized diffuse sources and determine two of these to be newly discovered giant radio relics. These two relics are located in the southeastern and northwestern outskirts of the cluster. The corresponding integrated spectral indices measure −1.81 ± 0.26 and −0.63 ± 0.21 for the SE and NW relics, respectively. From an X-ray surface brightness profile we also detect a possible density jump of R=1.39{sub −0.22}{sup +0.34} co-located with the newly discovered SE relic. This density jump would correspond to a shock front Mach number of M=1.26{sub −0.15}{sup +0.25}.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1976

Discovery of intense X-ray bursts from the globular cluster NGC 6624

A new type of time variation of cosmic X-ray sources has been found from the Astronomical Netherlands Satellite (ANS) observations of the source 3U 1820-30, associated with the globular cluster NGC 6624. Two bursts in the 1-30 keV X-ray intensity of this source are reported. Each displayed a rapid rise in flux (no more than 1 s) by a factor of 20-30 followed by an approximately 8-s exponential decay. These bursts appear to be qualitatively different from short time variations previously reported for X-ray sources. Analysis for further source variability, energy spectra, and position is presented. The characteristics of these events may imply the existence of a collapsed core in the globular cluster.

Grindlay, J.↗
NASA NTRS1988

Discovery of a possible X-ray triple - 4U 1915-05

The optical counterpart of the 50 minute binary and X-ray burst source 4U 1915-05 has been identified with a 21st mag blue object. Extensive CCD photometric observations show that the optical modulation of the system defines a period of 50.4567 minutes with high precision and is thus probably the true orbital period, whereas the range of X-ray ray dip period values (49.7-50.1 minutes) reported previously are excluded. A model is described whereby the optical modulation is due to partial eclipse of the rim of the accretion disk by a low-mass companion star and the X-ray dips are due to absorption and scattering by blobs of material above and below the disk plane and with density proportional to the current mass transfer rate from the companion star. The 1 percent difference in periods may suggest that the system is a hierarchical triple with a third companion star of low-mass orbiting the binary ion in an about 2.5 day retrograde orbit. The possible origin of such a system by tidal capture in a globular cluster, since disrupted, is briefly discussed.

Grindlay, J. E.↗
NASA NTRS1992

Discovery of intermediate redshift galaxy clusters in the ROSAT NEP field

We report preliminary results from a program to identify optical counterparts of ROSAT sources in the North Ecliptic Pole (NEP) region. The most striking X-ray feature reported by Hasinger et al. (1991) is an extended low surface brightness region of X-ray emission. Within the two X-ray contours of highest count rate we find a cluster of galaxies at a redshift of 0.09 and an early-type galaxy at a redshift of 0.03. X-ray emission from these objects may provide an explanation for the observed X-ray morphology. We also find evidence that other X-ray sources in this region are coincident with clusters or groups of galaxies at redshifts between 0.08 and 0.09. The presence of at least five X-ray detected clusters or groups in this narrow redshift band within a 1.5 deg radius field seems to indicate the existence of a moderate redshift supercluster. The existence of these clusters will have major implications for the study of large-scale structure through X-ray surveys such as ROSAT.

Burg, R.↗
DOE OSTI2020

Probing neutrino quantum decoherence at reactor experiments

We explore how well reactor antineutrino experiments can constrain or measure the loss of quantum coherence in neutrino oscillations. We assume that decoherence effects are encoded in the size of the neutrino wave-packet, σ . We find that the current experiments Daya Bay and the Reactor Experiment for Neutrino Oscillation (RENO) already constrain σ > 1 . 0 × 10 - 4 nm and estimate that future data from the Jiangmen Underground Neutrino Observatory (JUNO) would be sensitive to σ < 2 . 1 × 10 - 3 nm. If the effects of loss of coherence are within the sensitivity of JUNO, we expect σ to be measured with good precision. The discovery of nontrivial decoherence effects in JUNO would indicate that our understanding of the coherence of neutrino sources is, at least, incomplete.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Californium Electrodepositions at Oak Ridge National Laboratory

Electrodepositions of californium isotopes were successfully performed at Oak Ridge National Laboratory (ORNL) during the past year involving two different types of deposition solutions, ammonium acetate (NH 4 C 2 H 3 O 2 ) and isobutanol ((CH 3 ) 2 CHCH 2 OH). A californium product that was decay enriched in 251 Cf was recovered for use in super-heavy element (SHE) research. This neutron-rich isotope, 251 Cf, provides target material for SHE research for the potential discovery of heavier isotopes of Z=118. The californium material was recovered from aged 252 Cf neutron sources in storage at ORNL. These sources have decayed for over 30 years, thus providing material with a very high 251 Cf-to- 252 Cf ratio. After the source capsules were opened, the californium was purified and then electrodeposited using the isobutanol method onto thin titanium foils for use in an accelerator at the Joint Institute for Nuclear Research in Dubna, Russia. Another deposition method, ammonium acetate, was used to produce a deposition containing 1.7 0.1 Ci of 252 Cf onto a stainless steel substrate. This was the largest single electrodeposition of 252 Cf ever prepared. The 252 Cf material was initially purified using traditional ion exchange media, such as AG50-AHIB and AG50-HCl, and further purified using a TEVA-NH 4 SCN system to remove any lanthanides, resulting in the recovery of 3.6 0.1 mg of purified 252 Cf. The ammonium acetate deposition was run with a current of 1.0 amp, resulting in a 91.5% deposition yield. Purification and handling of the highly radioactive californium material created additional challenges in the production of these sources.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗