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At least 649 records · Page 36

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DOE OSTI2025

Cosmological Neutron Stars Produce Diffuse Axion X-Ray Signatures

Axion-like particles can be abundantly produced through scattering processes in the cores of neutron stars (NSs). If they are ultralight ($m_a \lesssim 10^{-4}$ eV), then they can efficiently convert to detectable photons in the external NS magnetospheres, and if they are heavy ($m_a \gtrsim 1$ eV), then they can decay into photons before reaching Earth. In this work, we search for the resulting X-ray signatures from both of these channels summing over the $\textit{cosmological}$ NS population. We compare the predicted axion-induced X-ray signal to the cosmic X-ray background today as measured by a number of instruments such as NuSTAR, HEAO, Swift, and INTEGRAL. We model the axion-induced signal using NS cooling simulations and magnetic field evolution models. We find no evidence for axions and derive strong constraints for both ultralight and heavy axion scenarios, covering new parameter space for the axion-photon and axion-nucleon couplings. Our results rule out the axion-explanation of the Magnificent Seven X-ray excess from nearby isolated NSs.

Cosmology and Nongalactic Astrophysics (astro-ph.C↗

NASA NTRS1971

Comets and nongravitational forces. IV.

Orbital elements and nongravitational parameters are derived from observations at every apparition of the periodic comets Honda-Mrkos-Pajdusakova, Faye, Tempel 2, Biela, Brorsen, and Tempel-Swift. For all except the first comet, the observations go back a century and more, although the last three comets have failed to reappear for some considerable time. The circumstances of the splitting of P/Biela are studied, and it is shown that the motion of the primary component was scarcely affected; it is also demonstrated that, if the primary still exists, it may pass only 0.05 AU from the earth in November 1971. An up-to-date list of mass-loss rates from comets is presented. It is found that, while most of the reliable determinations indicate that the cometary nongravitational effects decrease with time, there are a few cases where the effects increase slightly. The former situation is discussed in terms of a nuclear core-mantle model, implying that these comets will eventually evolve into inert, asteroidal objects, while the nuclei of the other comets are interpreted as coreless, eventually to disappear completely (or almost completely).

Marsden, B. G.↗

NASA NTRS1973

Computer programs: Operational and mathematical, a compilation

Several computer programs which are available through the NASA Technology Utilization Program are outlined. Presented are: (1) Computer operational programs which can be applied to resolve procedural problems swiftly and accurately. (2) Mathematical applications for the resolution of problems encountered in numerous industries. Although the functions which these programs perform are not new and similar programs are available in many large computer center libraries, this collection may be of use to centers with limited systems libraries and for instructional purposes for new computer operators.

Source record↗

NASA NTRS1975

Electroencephalographic studies of sleep

Various experimental studies on sleep are described. The following areas are discussed: (1) effect of altered day length on sleep, (2) effect of a partial loss of sleep on subsequent nocturnal sleep; (3) effect of rigid control over sleep-wake-up times; (4) sleep and wakefulness in a time-free environment; (5) distribution of spindles during a full night of sleep; and (6) effect on sleep and performance of swiftly changing shifts of work.

Webb, W. B.↗

NASA NTRS1975

LANDSAT-1 data as it has been applied for land use and water quality data by the Virginia State Water Control Board. 1: The state project. 2: Monitoring water quality from LANDSAT

LANDSAT-1 imagery has been used for water quality and land use monitoring in and around the Swift Creek and Lake Chesdin Reservoirs in Virginia. This has proved useful by (1) helping determine valid reservoir sampling stations, (2) monitoring areas not accessible by land or water, (3) giving the State a viable means of measuring Secchi depth readings in these inaccessible areas, (4) giving an overview of trends in changing sedimentation loadings over a given time period and classifying these waters into various categories, (5) enabling the State to inventory all major lakes and reservoirs and computing their acreage, (6) monitoring land use changes in any specific area, (7) evaluating possible long-term environmental effects of nearby developments, and (8) monitoring and predicting population shifts with possible impact on water quality problems. The main problems in the long-term use of such imagery appear to be cost and lack of consistency due to cloud cover limitations.

Trexler, P. L.↗

NASA NTRS1977

Relative motions of fragments of the split comets. I - A new approach

A hypothesis is proposed which interprets the relative motion of two fragments of a split comet in terms of a slight difference between their effective solar attraction rather than in terms of the impulse imparted to them at separation. A quantitative version of this hypothesis is formulated by assuming that the difference in effective solar attraction varies with heliocentric distance in direct proportion to the actual solar attraction so that the ratio of the two forces is constant and equal to a measure of the relative effect between the two fragments under consideration. Results obtained using this formulation are compared with observational evidence on the split comets P/Biela, Liais 1860 I, 1882 II, P/Brooks 2 1889 V, Swift 1899 I, Kopff 1905 IV, Mellish 1915 II, Taylor 1916 I, 1947 XII, Wirtanen 1957 VI, Ikeya-Seki 1965 VIII, Kohoutek 1970 III, and West 1975n. The hypothesis is found to fail only in the case of comet Wirtanen 1957 VI. Some unusual phenomena associated with split comets are examined.

Sekanina, Z.↗

NASA NTRS1980

Dynamical and photometric investigation of comets

The findings of dynamic and photometric investigations of comets are summarized, and include discussions of the comets Bennett 1970 II, Kohoutek 1973f, West 1976 VI, and periodic comets d'Arrest, Encke, and Swift Tuttle. The phenomena examined include striated and anomalous tails, tail composition and the dynamics of vaporizing dust particles, the evolution of dust jets, and split and dissipating comets.

Sekanina, Z.↗

NASA NTRS1982

An experimental investigation of the vaporous/gaseous cavity characteristics of an eccentric journal bearing

This paper describes the experimental pressure and temperature results obtained when rotating a shaft in an eccentric lucite casing at velocities ranging from 209 to 628 rad/s (2000 to 6000 rpm). The results are presented in terms of three-dimensional plots and contour maps. Photographic evidence is presented to illustrate how the downstream and upstream regions of the cavity develop and evolve into the well-known finger patterns. A comparison between pressure and temperature profiles in air-saturated oil and carbon dioxide-saturated oil is presented; the origin and nature of the gases contained in the cavity are discussed. Three analytical models (Swift-Stieber, separation, Floberg) predicting the formation of the cavitation zone are presented and evaluated in light of the experimental results. A motion-picture supplement depicting these results is available upon request.

Braun, M. J.↗

NASA NTRS1983

Human factors in space telepresence

The problems of interfacing a human with a teleoperation system, for work in space are discussed. Much of the information presented here is the result of experience gained by the M.I.T. Space Systems Laboratory during the past two years of work on the ARAMIS (Automation, Robotics, and Machine Intelligence Systems) project. Many factors impact the design of the man-machine interface for a teleoperator. The effects of each are described in turn. An annotated bibliography gives the key references that were used. No conclusions are presented as a best design, since much depends on the particular application desired, and the relevant technology is swiftly changing.

Akin, D. L.↗

NASA NTRS1984

Infrared photometry of the dust in comets

Infrared observations of six comets ranging in heliocentric distance from 1 to 5 AU are reported. Data consist of wide and intermediate bandpass filter photometry, 1-20 microns, for periodic comets Stephan-Oterma, Swift-Gehrels, Kearns-Kwee, Gunn, and Grigg-Skjellerup and for parabolic Comet Elias (1981 XV). All of the comets show infrared temperatures hotter than a theoretical black body, indicating small absorbing grains. No emission feature at 10 microns was observed within the accuracy of the filter photometry. The photometric system is discussed in detail, and temperature-dependent corrections to monochromatic magnitudes are presented.

Tokunaga, A. T.↗

NASA NTRS1984

Errors in radiometric remote sensing of sea-surface temperature and salinity

Techniques for remote measurement of sea-surface physical temperature and salinity using radiometric measurements from aircraft or satellite are reviewed. Studies have been conducted to determine the sensitivity of the errors in surface temperature and salinity to errors in the measured brightness temperatures using combinations of UHF, L, S, and C-band measurements. These investigations were made using values of conductivity, static dielectric constant, and relaxation time derived from the regression equations of Klein and Swift (1977). Results of the error sensitivity study are presented in the form of error contour plots which permit the calculation of errors in the estimation of the physical parameters for given errors in the raw radiometric measurements.

Britt, C. L., Jr.↗

NASA NTRS1986

Ultraviolet spectroscopy of meteoric debris of comets

It is proposed to carry out slitless spectroscopy at ultraviolet wavelengths from orbit of meteoric debris associated with comets. The Eta Aquarid and Orionid/Halley and the Perseid/1962 862 Swift-Tuttle showers would be principal targets. Low light level, ultraviolet video technique will be used during night side of the orbit in a wide field, earthward viewing mode. Data will be stored in compact video cassette recorders. The experiment may be configured as a GAS package or in the HITCHHIKER mode. The latter would allow flexible pointing capability beyond that offered by shuttle orientation of the GAS package, and doubling of the data record. The 1100 to 3200 A spectral region should show emissions of atomic, ionic, and molecular species of interest on cometary and solar system studies.

Wdowiak, T. J.↗

NASA NTRS1986

Ultraviolet spectroscopy of meteoric debris: In situ calibration experiments from Earth orbit

It is proposed to carry out slitless spectroscopy at ultraviolet wavelengths from orbit of meteoric debris associated with comets. The Eta Aquarid, Orionid/Halley, and the Persied/1962 862 Swift-Tuttle showers would be principal targets. Low light level, ultraviolet video technique will be used during night side of the orbit in a wide field, earthward viewing mode. Data will be stored in compact video cassette recorders. The experiment may be configured as a GAS package or in the HITCHHIKER mode. The latter would allow flexible pointing capability beyond that offered by shuttle orientation of the GAS package, and doubling of the data record. The 1100 to 3200 A spectral region should show emissions of atomic, ionic, and molecular species of interest on cometary and solar system studies.

Nuth, J. A., III↗

NASA NTRS1987

Workstations take over conceptual design

Workstations provide sufficient computing memory and speed for early evaluations of aircraft design alternatives to identify those worthy of further study. It is recommended that the programming of such machines permit integrated calculations of the configuration and performance analysis of new concepts, along with the capability of changing up to 100 variables at a time and swiftly viewing the results. Computations can be augmented through links to mainframes and supercomputers. Programming, particularly debugging operations, are enhanced by the capability of working with one program line at a time and having available on-screen error indices. Workstation networks permit on-line communication among users and with persons and computers outside the facility. Application of the capabilities is illustrated through a description of NASA-Ames design efforts for an oblique wing for a jet performed on a MicroVAX network.

Kidwell, George H.↗

NASA NTRS1988

Observed rate of ionization in shaped-charge releases of barium in the ionosphere

Data from 36 Ba shaped-charge releases carried out at an angle of less than 25 deg to the magnetic field, by the technique of Wescott et al. (1972) and Michel (1974), were examined for evidence of a sustained rate of ionization in excess of that attributable to sunlight. In four of the experiments, the time constant for the decay of the neutrals was measured using an ultrasensitive color TV camera and was found to have a value of about 30 sec, consistent with slow (solar) ionization. Although the qualitative appearance of most jets was found to be consistent with a slow process of ionization, some releases produced a thin confined jet that was suggestive of rapid ionization. Two of these jets were analyzed in detail, but no evidence of anomalous ionization was produced. The data obtained in this work agree with the geometrical predictions of the Swift model.

Hallinan, Thomas J.↗

NASA NTRS1987

Ultraviolet spectroscopy of meteoric debris: In situ calibration experiments from earth orbit

It is proposed to carry out slitless spectroscopy at ultraviolet wavelengths from orbit of meteoric debris associated with comets. The Eta Aquarid, Orionid/Halley, and the Persied/1962 862 Swift-Tuttle showers would be principal targets. Low light level, ultraviolet video technique will be used during the night side of the orbit in a wide field, earthward viewing mode. Data will be stored in compact video cassette recorders. The experiment may be configured as a GAS package or in the HITCHHIKER mode. The latter would allow flexible pointing capability beyond that offered by shuttle orientation of the GAS package, and doubling of the data record. The 1100 to 3200 A spectral region should show emissions of atomic, ionic, and molecular species of interest on cometary and solar system studies.

Nuth, Joseph A.↗

NASA NTRS1990

Calculation of polarization and anisotropy of resonant and fluorescent scattering

Formulas are derived for the swift calculation of the angular intensity distribution and the degree of polarization associated with the resonant and fluorescent scattering of radiation by atoms which occurs in the rarefied upper atmospheres of planets during sunlit airglow phenomena. Attention is given to spectral lines with hyperfine structure, which are indicative of nuclear spin processes. The method employed involves summations over Zeeman components, allowing an evaluation of polarization through the addition of underlying simple resonant and fluorescent scattering channels.

Chamberlain, Joseph W.↗

NASA NTRS1990

A simple parcel method for prediction of cumulus onset and area-averaged cloud amount over heterogeneous land surfaces

A set of PBL data selected from the Wangara experiment is used to examine the relationship between cumulus amount and the calculated relative humidity of rising parcels. The Wilde et al. (1985) method is compared to two explicit parcel methods. It is shown that predictions using parcel methods, in which surface air is lifted to its equilibrium level while being diluted by a defined amount of mixed layer air, are superior for cloud amount, especially during periods of rapid cloud onset when the mean boundary layer top is swiftly rising through a near-neutral layer. Pending independent verification, it appears that an rms error in instantaneous cloud amount of + or - 10 percent may be achievable.

Wetzel, Peter J.↗