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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 1,171 records · Page 65
All sourcesNASA NTRSDOE OSTI
DOE OSTI2015

Cosmic matrix in the jubilee of relativistic astrophysics

Following the classical works on Neutron Stars, Black Holes and Cosmology, I outline some recent results obtained in the IRAP-PhD program of ICRANet on the “Cosmic Matrix”: a new astrophysical phenomenon recorded by the X- and Gamma-Ray satellites and by the largest ground based optical telescopes all over our planet. In 3 minutes it has been recorded the occurrence of a “Supernova”, the “Induced-Gravitational-Collapse” on a Neutron Star binary, the formation of a “Black Hole”, and the creation of a “Newly Born Neutron Star”. This presentation is based on a document describing activities of ICRANet and recent developments of the paradigm of the Cosmic Matrix in the comprehension of Gamma Ray Bursts (GRBs) presented on the occasion of the Fourteenth Marcel Grossmann Meeting on Recent Developments in Theoretical and Experimental General Relativity, Gravitation, and Relativistic Field Theory. A Portuguese version of this document can be downloaded at: http://www.icranet.org/documents/brochure{sub i}cranet{sub p}t.pdf.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2022

A 20 Gbps PAM4 data transmitter ASIC for particle physics experiments

We present the design and test results of a novel data transmitter ASIC operating up to 20.48 Gbps with 4-level Pulse-Amplitude-Modulation (PAM4) for particle physics experiments. This ASIC, named GBS20, is fabricated in a 65 nm CMOS technology. Two serializers share a 5.12 GHz Phase Locked Loop (PLL) clock. The outputs from the serializers are combined into a PAM4 signal that directly drives a Vertical-Cavity-Surface-Emitting-Laser (VCSEL). The input data channels, each at 1.28 Gbps, are scrambled with an internal 2$^{7}$-1 Pseudo-Random Binary Sequence (PRBS), which also serves as a frame aligner. GBS20 is tested to work at 10.24 and 20.48 Gbps with a VCSEL-based Transmitter-Optical-Subassembly (TOSA). The power consumption of GBS20 is below 238 mW and reduced to 164 mW in the low-power mode.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2024

Phase stability in the Hf-N and Zr-N systems

Hf and Zr nitrides are promising compounds for many technologically important areas, including high-temperature structural applications, quantum computing, and solar and optical applications. Here, this article reports on a comprehensive first-principles statistical mechanics study of phase stability in the Hf-N and Zr-N binary systems. A high solubility of nitrogen in the hcp forms of Hf and Zr is predicted. The rocksalt forms of HfN and ZrN can also tolerate a high degree of off-stoichiometry through the introduction of nitrogen and metal vacancies. The Hf-N binary favors a family of stacking faulted parent crystal structures at intermediate nitrogen concentrations that host a unique form of short-range order among nitrogen interstitials and vacancies. These phases can accommodate some degree of configurational entropy and remain ordered to temperatures as high as 1200 K.

Monte Carlo methods↗
DOE OSTI2017

Chandra Detection of Intracluster X-Ray sources in Virgo

We present a survey of X-ray point sources in the nearest and dynamically young galaxy cluster, Virgo, using archival Chandra observations that sample the vicinity of 80 early-type member galaxies. The X-ray source populations at the outskirts of these galaxies are of particular interest. We detect a total of 1046 point sources (excluding galactic nuclei) out to a projected galactocentric radius of ∼40 kpc and down to a limiting 0.5–8 keV luminosity of ∼2×10{sup 38} erg s{sup −1}. Based on the cumulative spatial and flux distributions of these sources, we statistically identify ∼120 excess sources that are not associated with the main stellar content of the individual galaxies, nor with the cosmic X-ray background. This excess is significant at a 3.5σ level, when Poisson error and cosmic variance are taken into account. On the other hand, no significant excess sources are found at the outskirts of a control sample of field galaxies, suggesting that at least some fraction of the excess sources around the Virgo galaxies are truly intracluster X-ray sources. Assisted with ground-based and HST optical imaging of Virgo, we discuss the origins of these intracluster X-ray sources, in terms of supernova-kicked low-mass X-ray binaries (LMXBs), globular clusters, LMXBs associated with the diffuse intracluster light, stripped nucleated dwarf galaxies and free-floating massive black holes.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1973

X-ray pulse profile and celestial position of Hercules X-1.

The celestial position of the binary X-ray source Her X-1 has been measured with a precision of 30 sec and, within the uncertainties, agrees with the position of the optical variable HZ Herculis. An average light curve for the 1.24-sec periodicity has been obtained with about 10-msec resolution. The average pulse is a double-peaked structure which shows significant intensity changes in time scales down to 30 msec.

Doxsey, R.↗
NASA NTRS1995

The difference between radio-loud and radio-quiet active galaxies

The recent development of unified theories of active galactic nuclei (AGNs) has indicated that there are two physically distinct classes of these objects--radio-loud and radio-quiet. Despite differences, the (probable) thermal emissions from the AGNs (continua and lines from X-ray to infrared wavelengths) are quite similar to the two classes of object. We argue that this last result suggests that the black hole masses and mass accretion rates in the two classes are not greatly different, and that the difference between the classes is associated with the spin of the black hole. We assume that the normal process of accretion through a disk does not lead to rapidly spinning holes and propose that galaxies (e.g., spirals) which have not suffered a recent major merger event contain nonrotating or only slowly rotating black holes. When two such galaxies merge, the two black holes are known to form a binary and we assume that they eventually coalesce. The ratio of the number of radio-loud to radio-quiet AGNs at a given thermal (e.g., optical) luminosity is determined by the galaxy merger rate. Comparisons between the predicted and observed radio luminosity functions constrain the efficiencies with which jet power is extracted from the spinning hole and radio emission is produced by the jet.

Wilson, A. S.↗
NASA NTRS1998

The Outbursts and Orbit of the Accreting Pulsar GS 1843-02=2S 1845-024

We present observations of a series of 10 transient outbursts of pulsed hard x-ray flux from the 10.6 mHz accreting pulsar GS 1843-02 using the Burst and Transient Source Experiment (BATSE) on the Compton Observatory. These outbursts occurred regularly every 242 days, coincident with the ephemeris of the periodic transient GRO J1849-03 (Zhang et al. 1996)), which has recently been identified with the the SAS 3 source 2S 1845-024 (Soffitta et al. 1998). Our pulsed detection provides the first clear identification of GS 1843-02 with 2S 1845-024. We present a pulse timing analysis which shows that the 2S 1845-024 outbursts occur near the periastron passage of a highly eccentric (e = 0.88 q 0.01) 242.18 +/- 0.01 day period binary orbit about a high mass (M(sub opt) > 7 solar mass companion. The orbit and transient outburst pattern suggest a Be star/X-ray pulsar system, however the optical companion is unknown. Our observations show a long-term spin-up trend, with most of the spin-up occurring during the outbursts. From the measured spin-up rates and inferred mass accretion rates we conclude that an accretion disk is present during the outbursts.

Finger, Mark H.↗
NASA NTRS2002

The Stellar Imager (SI) Mission Concept

The Stellar Imager (SI) is envisioned as a space-based, UV-optical interferometer composed of 10 or more one-meter class elements distributed with a maximum baseline of 0.5 km. It is designed to image stars and binaries with sufficient resolution to enable long-term studies of stellar magnetic activity patterns, for comparison with those on the sun. It will also support asteroseismology (acoustic imaging) to probe stellar internal structure, differential rotation, and large-scale circulations. SI will enable us to understand the various effects of the magnetic fields of stars, the dynamos that generate these fields, and the internal structure and dynamics of the stars. The ultimate goal of the mission is to achieve the best-possible forecasting of solar activity as a driver of climate and space weather on time scales ranging from months up to decades, and an understanding of the impact of stellar magnetic activity on life in the Universe. In this paper we describe the scientific goals of the mission, the performance requirements needed to address these goals, the "enabling technology" development efforts being pursued, and the design concepts now under study for the full mission and a possible pathfinder mission.

Carpenter, Kenneth G.↗
NASA NTRS2005

RXTE timing and spectroscopy of black hole binary in outburst

Under this program, Rossi X-ray timing explorer (RXTE) made observations of the Galactic black hole X-ray binary GX 339-4. These observations were timed to be simultaneous with Chandra observations of the same source. Supporting multi-wavelength observations were also obtained using optical and radio telescopes. The RXTE data have been partially analyzed, and will be published in a paper summarizing both the Chandra and RXTE spectral results. The RXTE spectra are instrumental in defining the continuum spectrum in the Chandra data. Moreover, the timing properties measured with RXTE are essential to diagnosing the "state" of the black hole when it was observed by the array of telescopes organized for this effort.

Swank, Jean↗
DOE OSTI2010

The Formation of Population III Binaries from Cosmological Initial Conditions

Previous high resolution cosmological simulations predict the first stars to appear in the early universe to be very massive and to form in isolation. Here we discuss a cosmological simulation in which the central 50M{sub {circle_dot}} clump breaks up into two cores, having a mass ratio of two to one, with one fragment collapsing to densities of 10{sup -8}g cm{sup -3}. The second fragment, at a distance of {approx}800 astronomical units, is also optically thick to its own cooling radiation from molecular hydrogen lines, but is still able to cool via collision-induced emission. The two dense peaks will continue to accrete from the surrounding cold gas reservoir over a period of {approx} 10{sup 5} years and will likely form a binary star system.

08 HYDROGEN↗
NASA NTRS1984

LSS 4300 - A hot counterpart of Upsilon Sagittarii and KS Persei?

A number of recent observations indicate that the star LSS 4300 (HDE 320156) is a high-temperature analog of the hydrogen-deficient binaries Upsilon Sgr and KS Per. A preliminary model-atmosphere analysis based on high dispersion spectra obtained at Kitt Peak and Cerro Tololo yields Teff = 14,400 K, log (g) = 1.4, n(H)/n(He) = 0.003, and n(N)/n(C) = 20 for the visible component. The optical emission-line spectrum of LSS 4300 is nearly identical to that of Upsilon Sgr, including strong, broad H-alpha, Fe II, and forbidden Ca II emission; and JHKL photometry obtained at Cerr Tololo reveals an infrared excess nearly identical to that of Upsilon Sgr. It is suggested that LSS 4300, like Upsilon Sgr and KS Per, is a close binary system consisting of a helium supergiant of about 1 solar mass, which is undergoing its second mass loss, and a less luminous secondary, which is accreting matter from the primary.

Schoenberner, D.↗
DOE OSTI2016

DISCOVERY OF AN X-RAY-EMITTING CONTACT BINARY SYSTEM 2MASS J11201034−2201340

We report the detection of orbital modulation, a model solution, and the X-ray properties of a newly discovered contact binary, Two Micron All Sky Survey (2MASS) J11201034−2201340. We serendipitously found this X-ray point source outside the error ellipse when searching for possible X-ray counterparts of γ-ray millisecond pulsars among the unidentified objects detected by the Fermi Gamma-ray Space Telescope. The optical counterpart of the X-ray source (unrelated to the γ-ray source) was then identified using archival databases. The long-term Catalina Real-Time Transient Survey detected a precise signal with a period of P=0.28876208(56) days. A follow-up observation made by the Super Light Telescope of Lulin Observatory revealed the binary nature of the object. Utilizing archived photometric data of multi-band surveys, we construct the spectral energy distribution (SED), which is well fit by a K2V spectral template. The fitting result of the orbital profile using the Wilson–Devinney code suggests that 2MASS J11201034-2201340 is a short-period A-type contact binary and the more massive component has a cool spot. The X-ray emission was first noted in observations made by Swift, and then further confirmed and characterized by an XMM-Newton observation. The X-ray spectrum can be described by a power law or thermal Bremsstrahlung. Unfortunately, we could not observe significant X-ray orbital modulation. Finally, according to the SED, this system is estimated to be 690 pc from Earth with a calculated X-ray intensity of (0.7−1.5)×10{sup 30} erg s{sup −1}, which is in the expected range of an X-ray emitting contact binary.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2020

Wide Band Gap Chalcogenide Semiconductors

Wide band gap semiconductors are essential for today’s electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. The most intensively investigated wide band gap semiconductors are transparent conductive oxides (TCOs), such as tin-doped indium oxide (ITO) and amorphous In–Ga–Zn–O (IGZO), used in displays and solar cells, carbides (e.g., SiC) and nitrides (e.g., GaN) used in power electronics, and emerging halides (e.g., γ-CuI) and 2D electronic materials (e.g., graphene) used in various optoelectronic devices. Compared to these prominent materials families, chalcogen-based (Ch = S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out because of their propensity for p-type doping, high mobilities, high valence band positions (i.e., low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent semiconductors, as well as the theoretical and experimental underpinnings of the corresponding research methods. We proceed to summarize progress in wide band gap (EG > 2 eV) chalcogenide materials—namely, II–VI MCh binaries, CuMCh 2 chalcopyrites, Cu 3 MCh 4 sulvanites, mixed-anion layered CuMCh(O,F), and 2D materials—and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. Then, we finally review applications—for example, photovoltaic and photoelectrochemical solar cells, transistors, and light emitting diodes—that employ wide band gap chalcogenides as either an active or passive layer. Overall, by examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this Review aims to inspire continued research on this emerging class of transparent semiconductors and thereby enable future innovations for optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2013

INFRARED OBSERVATIONS OF THE MILLISECOND PULSAR BINARY J1023+0038: EVIDENCE FOR THE SHORT-TERM NATURE OF ITS INTERACTING PHASE IN 2000-2001

We report our multi-band infrared (IR) imaging of the transitional millisecond pulsar system J1023+0038, a rare pulsar binary known to have an accretion disk in 2000-2001. The observations were carried out with ground-based and space telescopes from near-IR to far-IR wavelengths. We detected the source in near-IR JH bands and Spitzer 3.6 and 4.5 {mu}m mid-IR channels. Combined with the previously reported optical spectrum of the source, the IR emission is found to arise from the companion star, with no excess emission detected in the wavelength range. Because our near-IR fluxes are nearly equal to those obtained by the 2MASS all-sky survey in 2000 February, the result indicates that the binary did not contain the accretion disk at the time, whose existence would have raised the near-IR fluxes to twice larger values. Our observations have thus established the short-term nature of the interacting phase seen in 2000-2001: the accretion disk existed for at most 2.5 yr. The binary was not detected by the WISE all-sky survey carried out in 2010 at its 12 and 22 {mu}m bands and our Herschel far-IR imaging at 70 and 160 {mu}m. Depending on the assumed properties of the dust, the resulting flux upper limits provide a constraint of <3 Multiplication-Sign 10{sup 22}-3 Multiplication-Sign 10{sup 25} g on the mass of the dust grains that possibly exist as the remnants of the previously seen accretion disk.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2023

Finding Multiply Lensed and Binary Quasars in the DESI Legacy Imaging Surveys

The time delay between multiple images of strongly lensed quasars is a powerful tool for measuring the Hubble constant ( H 0 ). To achieve H 0 measurements with higher precision and accuracy using the time delay, it is crucial to expand the sample of lensed quasars. We conduct a search for strongly lensed quasars in the Dark Energy Spectroscopic Instrument (DESI) Legacy Imaging Surveys. The DESI Legacy Surveys comprise 19,000 deg 2 of the extragalactic sky observed in three optical bands ( g , r , and z ), making it well suited for the discovery of new strongly lensed quasars. We apply an autocorrelation algorithm to ~5 million objects classified as quasars in the DESI Quasar Sample. These systems are visually inspected and ranked. Here, we present 436 new multiply lensed and binary quasar candidates, 65 of which have redshifts from Sloan Digital Sky Survey Data Release 16. We provide redshifts for an additional 18 candidates from the SuperNova Integral Field Spectrograph.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

Binary Millisecond Pulsar Discovery via Gamma-Ray Pulsations

We present that millisecond pulsars, old neutron stars spun up by accreting matter from a companion star, can reach high rotation rates of hundreds of revolutions per second. Until now, all such “recycled” rotation-powered pulsars have been detected by their spin-modulated radio emission. In a computing-intensive blind search of gamma-ray data from the Fermi Large Area Telescope (with partial constraints from optical data), we detected a 2.5-millisecond pulsar, PSR J1311-3430. This unambiguously explains a formerly unidentified gamma-ray source that had been a decade-long enigma, confirming previous conjectures. Lastly, the pulsar is in a circular orbit with an orbital period of only 93 minutes, the shortest of any spin-powered pulsar binary ever found.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2012

THE NATURE OF TRANSITION CIRCUMSTELLAR DISKS. III. PERSEUS, TAURUS, AND AURIGA

As part of an ongoing program aiming to characterize a large number of Spitzer-selected transition disks (disks with reduced levels of near-IR and/or mid-IR excess emission), we have obtained (sub)millimeter wavelength photometry, high-resolution optical spectroscopy, and adaptive optics near-infrared imaging for a sample of 31 transition objects located in the Perseus, Taurus, and Auriga molecular clouds. We use these ground-based data to estimate disk masses, multiplicity, and accretion rates in order to investigate the mechanisms potentially responsible for their inner holes. Following our previous studies in other regions, we combine disk masses, accretion rates, and multiplicity data with other information, such as spectral energy distribution morphology and fractional disk luminosity, to classify the disks as strong candidates for the following categories: grain-growth-dominated disks (seven objects), giant planet-forming disks (six objects), photoevaporating disks (seven objects), debris disks (11 objects), and cicumbinary disks (one object, which was also classified as a photoevaporating disk). Combining our sample of 31 transition disks with those from our previous studies results in a sample of 74 transition objects that have been selected, characterized, and classified in a homogenous way. We discuss this combined high-quality sample in the context of the current paradigm of the evolution and dissipation of protoplanetary disks and use its properties to constrain different aspects of the key processes driving their evolution. We find that the age distribution of disks that are likely to harbor recently formed giant planets favors core accretion as the main planet formation mechanism and a {approx}2-3 Myr formation timescale.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2010

DYNAMICAL K EDGE AND LINE VARIATIONS IN THE X-RAY SPECTRUM OF THE ULTRA-COMPACT BINARY 4U 0614+091

We observed the ultra-compact binary candidate 4U 0614+091 for a total of 200 ks with the high-energy transmission gratings on board the Chandra X-ray Observatory. The source is found at various intensity levels with spectral variations present. X-ray luminosities vary between 2.0 x 10{sup 36} erg s{sup -1} and 3.5 x 10{sup 36} erg s{sup -1}. Continuum variations are present at all times and spectra can be fit well with a power-law component, a high kT blackbody component, and a broad line component near oxygen. The spectra require adjustments to the Ne K edge and in some occasions also to the Mg K edge. Once further resolved, the Ne K edge region appears variable in terms of optical depths and morphology. The edge vicinity reveals an average velocity smear of {approx}3500 km s{sup -1} implying a characteristic radius of the order of <10{sup 9} cm consistent with an ultra-compact binary nature. The variability proves that the excess is intrinsic to the source. The data seem to indicate excess column densities of up to several 10{sup 18} cm{sup -2}. However, there are some serious problems with an Ne I interpretation in ultra-compact disks and we need to consider alternative interpretations, which include a variable O VIII ionization edge, as likely candidates. We test such possibilities with existing observations. The prominent soft emission line complex near the O VIII Ly{sub {alpha}} position appears extremely broad and relativistic effects from near the innermost disk have to be included. Gravitationally broadened line fits also provide nearly edge-on angles of inclination consistent with the observed high dynamics near the Ne K edge. The emissions appear consistent with an ionized disk with ionization parameters of the order of 10{sup 4} at radii of a few 10{sup 7} cm. The line wavelengths with respect to O VIII Ly{sub {alpha}} are found variably blueshifted indicating more complex inner disk dynamics.

79 ASTRONOMY AND ASTROPHYSICS↗