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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 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

The IPAC Image Subtraction and Discovery Pipeline for the Intermediate Palomar Transient Factory

We describe the near real-time transient-source discovery engine for the intermediate Palomar Transient Factory (iPTF), currently in operations at the Infrared Processing and Analysis Center (IPAC), Caltech. We coin this system the IPAC/iPTF Discovery Engine (or IDE). We review the algorithms used for PSF-matching, image subtraction, detection, photometry, and machine-learned (ML) vetting of extracted transient candidates. We also review the performance of our ML classifier. For a limiting signal-to-noise ratio of 4 in relatively unconfused regions, bogus candidates from processing artifacts and imperfect image subtractions outnumber real transients by approximately equal to 10:1. This can be considerably higher for image data with inaccurate astrometric and/or PSF-matching solutions. Despite this occasionally high contamination rate, the ML classifier is able to identify real transients with an efficiency (or completeness) of approximately equal to 97% for a maximum tolerable false-positive rate of 1% when classifying raw candidates. All subtraction-image metrics, source features, ML probability-based real-bogus scores, contextual metadata from other surveys, and possible associations with known Solar System objects are stored in a relational database for retrieval by the various science working groups. We review our efforts in mitigating false-positives and our experience in optimizing the overall system in response to the multitude of science projects underway with iPTF.

methods: analytical – methods: data analysis –↗
NASA NTRS1986

Radio observations of galactic bulge and globular cluster X-ray sources

A program of VLA observations of luminous X-ray sources in the Galactic bulge and globular clusters has been undertaken. Faint radio sources have been found as the counterparts of several Galactic bulge X-ray sources. Discovery of a relatively bright radio counterpart for GX 13 + 1 has allowed a much more precise source position to be obtianed and a likely IR identification to be made. The results suggest that the radio emission may be nonthermal. Comparison of the results with those of Geldzahler (1983) shows that the radio emission from Galactic bulge X-ray sources is highly variable by factors of at least three. Extended ratio monitoring could yield the long-sought binary periods for these objects.

Grindlay, Jonathan E.↗
NASA NTRS1995

Our planetary system: The solar system

A survey is given of the accomplishments of airborne astronomy in solar-system science. They include identification of sulfuric acid in the clouds of Venus, establishment of Jupiter's internal heat source, discovery of water vapor and almost a dozen other molecules in Jupiter's atmosphere, important measurements of occultations of stars by Mars, Pluto, and Chiron, discovery of the rings of Uranus, and diagnosis of mineral composition on planetary surfaces.

Hunten, Donald M.↗
NASA NTRS1991

On the possible bipolar nature of 21 micron IRAS sources

The discovery of another IRAS source (22574 + 6609) showing the unidentified 21-micron emission feature is reported. Its overall energy distribution is similar to the well-known edge-on bipolar nebulae AFGL 2688 and AFGL 618. Ground-based optical and infrared observations of this object and two other 21-micron sources show that while all three have very similar infrared properties, they differ greatly in the visual region. All three of these 21-micron sources are intrinsically similar bipolar nebulae, viewed at different orientations.

Hrivnak, Bruce J.↗
NASA NTRS1983

A new AM Her-like X-ray source

The discovery of a new X ray source associated with a binary and classifiable as a member of the AM Her class of objects is reported. The object was located with a detector on the HEAO A-2 spacecraft and by the imaging proportional counter on the Einstein Observatory. Detection occurred in the 0.15-0.4 keV band, and intensity variations of a factor of 2 were observed to happen on a time scale of around 2 hr. A location error box 0.9 deg on a side was constructed from the 2.95 deg overlapping FWHM field of view of the HEAO detector. The object, designated HO139-68, was reexamined using photometric and spectroscopic scans of it and the companion, which has been observed to be an ordinary late type star. Evidence for the presence of a magnetic white dwarf in the binary is discussed, noting indications of cyclotron emission. The X ray source flux is estimated to be 2.3/10 billion erg per sq cm per sec.

Agrawal, P. C.↗
NASA NTRS1978

On two new X-ray sources in the SMC and the high luminosities of the Magellanic X-ray sources

The discovery of two new X-ray sources, SMC X-2 and SMC X-3, in the Small Magellanic Cloud is reported. They have hard spectra, and their luminosities in the energy range 2-11 keV are 1.0 and 0.7 by 10 to the 38th power erg/sq cm per sec, respectively. It is shown that the luminosity distribution of the known Magellanic X-ray sources, which are now nine in number, is shifted toward higher luminosities with respect to that of similar sources in the Galaxy, and that the cause of the shift is probably an underabundance of heavy elements in the material accreted by the X-ray sources.

Clark, G.↗
NASA NTRS1987

The discovery of a source of repeated soft short gamma bursts in Sagittarius

Twelve short cosmic gamma-ray bursts were observed during July-December, 1983. The results of the localization of this source on the basis of Prognoz-9 and ICE data are presented. The source is situated 10 deg away from the Galactic Center. These localizations indicate that the January 7, 1979 burst originated from the same source.

Atteia, J. L.↗
NASA NTRS1988

Broad-wing molecular lines without internal energy sources

The discovery of broad CO wings in four high-latitude molecular clouds which do not have associated internal energy sources is reported. The velocity width of the wings is as much as five times greater than the width of the cloud cores. Neither visible stars brighter than the background population, optical nebulosity, nor IRAS point sources are found at the position of the wings, except for one case with an IRAS source 3 arcmin from the peak position of the wings. The possibility that the wings are the result of conductive interfaces resulting from cold molecular clouds in a hotter ambient medium is examined, and it is concluded that the expected column density of such gas is more than three orders of magnitude smaller than that observed.

Blitz, Leo↗
NASA NTRS1986

H0538 + 608 - A bright AM Herculis-type X-ray source

The discovery of an AM Herculis-type magnetic variable, an accreting binary system that contains a magnetic white dwarf and a late-type companion, is reported. The proposed optical counterpart to the detected X-ray source exhibits all the optical emission characteristics of its class: circular polarization, strongly modulated brightness variations, intense flickering on time scales of seconds, historical 'low states', and intense emission lines, including very strong lines of He II. The modulations in the polarization and the photometric magnitude suggest an orbital period of 3.1 + or -0.2 hr.

Remillard, R. A.↗
NASA NTRS2024

JWST Sighting of Decameter Main-Belt Asteroids and View on Meteorite Sources

Asteroid discoveries are essential for planetary-defense efforts aiming to prevent impacts with Earth, including the more frequent megaton explosions from decameter impactors. While large asteroids (≥100 km) have remained in the main belt since their formation, small asteroids are commonly transported to the near-Earth object (NEO) population. However, due to the lack of direct observational constraints, their size-frequency distribution — which informs our understanding of the NEOs and the delivery of meteorite samples to Earth —varies significantly among models. Here, we report 138 detections of the smallest asteroids (⪆10 m) ever observed in the main belt, which were enabled by JWST’s infrared capabilities covering the asteroids’ emission peaks and synthetic tracking techniques. Despite small orbital arcs, we constrain the objects’ distances and phase angles using known asteroids as proxies, allowing us to derive sizes via radiometric techniques. Their size-frequency distribution exhibits a break at∼100 m (debiased cumulative slopes of q=−2.66±0.60 and−0.97±0.14 for diameters smaller and larger than∼100 m, respectively), suggestive of a population driven by collisional cascade. These asteroids were sampled from multiple asteroid families —most likely Nysa, Polana and Massalia — according to the geometry of pointings considered here. Through additional long-stare infrared observations, JWST is poised to serendipitously detect thousands of decameter-scale asteroids across the sky, probing individual asteroid families and the source regions of meteorites “in-situ”.

asteroid families↗
NASA NTRS1980

Detection of energetic hydrogen molecules in Jupiter's magnetosphere by Voyager 2 - Evidence for an ionospheric plasma source

The discovery of energetic (approximately 1 MeV/nuc) H3 and H2 molecules in Jupiter's magnetosphere is reported. The data, obtained with the LECP instrument on Voyager 2, showed these molecules to be present throughout the magnetosphere and as far as 180 Jupiter radii from the planet, in the 'magnetospheric wind' region. Although the relative abundances of H3 and H2 do not show a monotonic trend with distance from Jupiter, the intervals of highest abundance were found in the outer magnetosphere. As an example, in the radial range 51-56 Jupiter radii, of the dayside magnetosphere, the abundances of H3 and H2 (0.60-0.95 MeV/nuc) were about 20 and 13-25% that of He, respectively, and the He abundance was about 1-2% that of H. Since H3(+) is expected to be an important constituent of Jupiter's ionosphere, the data provide strong evidence that, in addition to Io, the ionosphere may be an important local plasma source for the Jovian energetic particles. The measurements reported may represent the first detection in nature of molecules at energies as high as 1 MeV/nucleon.

Hamilton, D. C.↗
NASA NTRS1986

The Gamma-Ray Spectrometer Experiment on the Solar Maximum Mission Satellite

Observations by the Gamma-Ray Spectrometer (GRS) on the Solar Maximum Mission (SMM) are examined. This detector system is sensitive to high-energy X-rays, gamma-rays, and energetic neutrons. These neutral quanta provide a probe of the highest energy processes in a flare. The GRS has recorded over 150 flares since launch. In addition to the solar discoveries, the SMM GRS has made important discoveries about cosmic gamma-ray sources. These discoveries are summarized.

Chupp, E. L.↗
NASA NTRS1981

X-ray emission from galaxies and the universe

The study of X-ray emission from normal galaxies began with the launch of the Einstein Observatory in 1978. Galaxies of all Hubble types and point sources are discussed. It is concluded that statistical studies of bright Galactic sources, which relate to their evolution, are reliant upon the discovery of sources in many galaxies. It is also concluded that a substantial future increase (the Virgo cluster galaxies) requires a telescope system with better than arcminute resolution and a sensitivity better than 10 x that of Einstein.

Fabian, A. C.↗
NASA NTRS1989

Discovery of new 2 micron sources in Rho Ophiuchi

A 144-sq-arcmin region of the Rho Oph star-forming cloud core was surveyed at 2.2 microns, complete to mK = 14. A total of 61 sources are detected, 26 of which have been previously reported, accounting for a total of 35 new sources with mK = 12-14. There is no turnover in the 2-micron luminosity function of the Rho Oph cloud core to a limiting sensitivity of mK = 14. Two of the newly discovered sources are binary companions to previously cataloged objects.

Barsony, M.↗
NASA NTRS1990

On the feasibility of detecting extrasolar planets by reflected starlight using the Hubble Space Telescope

The best metrology data extant are presently used to estimate the center and wing point-spread function of the HST, in order to ascertain the implications of an observational criterion according to which a faint source's discovery can occur only when the signal recorded near its image's location is sufficiently larger than would be expected in its absence. After defining the maximum star-planet flux ratio, a figure of merit Q, defined as the contrast ratio between a 'best case' planet and the scattered starlight background, is introduced and shown in the HST's case to be unfavorable for extrasolar planet detection.

Brown, Robert A.↗
NASA NTRS1992

Gamma ray burst astrometry 2: Numerical tests

Since the announcement of the discovery of sources of gamma ray radiation in 1973, many more reports of such bursts have been published. Numerous artificial satellites have been equipped with gamma ray detectors including GRO. Unfortunately, almost no progress has been made in identifying the sources of this high energy radiation. Only one visible counterpart is known. It is suspected that this is a consequence of the methods currently used to define gamma ray burst source 'error boxes'. An alternative procedure was proposed in 1988 by Taff. Herein, Monte Carlo simulations are reported of the efficacy of this technique using realistic burst timing uncertainties and satellite location errors as well as a variety of satellite constellations. Since these are controlled numerical experiments, the dependence is examined of the statistics of the errors in the deduced burst wavefront normal as a function of the timing inconsistencies, detector location standard deviations, and especially the number and distribution of the detectors. The results clearly show that an arc minute prediction of a unique burst location is routinely obtainable once there are at least two interplanetary detectors.

Taff, L. G.↗