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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 127 records · Page 7
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NASA NTRS1994

Delta WIND Mission Science Briefing

The science objectives of the WIND mission are to: 1) provide complete plasma, energetic particle, and magnetic field input for magnetospheric and ionospheric studies; 2) Determine the magnetospheric output to interplanetary space in the up-stream region; 3) Investigate basic plasma processes occurring in the near-Earth solar wind; and 4) Provide baseline ecliptic plane observations to be used in heliospheric latitudes from ULYSSES. The WIND science briefing is presented by George Diller, NASA public affairs; Dr. Robert L. Carovillano, Project Scientist for the Global Geospace Science Initiative, NASA Headquarters; Dr. Mario H. Acuna, Project Scientist for the WIND Project, Goddard Space Flight Center (GSFC); Dr. Keith W. Ogilvie, Principle Investigator, Solar Wind Experiment at GSFC; Dr. Jean Louis Bougeret, Principle Investigator, Radio/Plasma Wave Experiment, Paris; and Dr. Eugeny Mazets, Co-Principle Investigator, Russian Gamma Ray Spectrometer Instrument, St. Pertersburg, Russia. Dr. Carovillano presents a cartoon slide of the Solar Terrestrial System and describes the Sun and the Magnetic field of the Earth. Dr. Acuna also presents a cartoon slide describing GEOTAIL, POLAR, WIND, SOHO, ULYSSES and Cluster which are the various tools used to study the complex solar terrestrial system. Dr. Ogilvie explains four particle and wave instruments on WIND. These instruments will be used to study the contributions and characteristics of plasma and plasma waves that occur in the solar wind. Dr. Bougeret explains the European participation in the WIND mission. He also shows a slide presentation of SOHO and the CLUSTER spacecraft. Dr. Mazets explains the main objective of the Transient Gamma Ray Spectrometer (TGRS) aboard the WIND spacecraft, which is to perform high resolution measurements of Gamma Ray Burst spectra and time histories, with emphasis on the search for line features in the energy spectra. The briefing ends with a question and answer period. See NONP-NASA-VT-2000078325 for additional question and answer footage.

Source record↗
NASA NTRS2001

Continued Analysis of EUVE Solar System Observations

This is the final report for this project. We proposed to continue our work on extracting important results from the EUVE (Extreme UltraViolet Explorer) archive of lunar and jovian system observations. In particular, we planned to: (1) produce several monochromatic images of the Moon at the wavelengths of the brightest solar EUV emission lines; (2) search for evidence of soft X-ray emissions from the Moon and/or X-ray fluorescence at specific EUV wavelengths; (3) search for localized EUV and soft X-ray emissions associated with each of the Galilean satellites; (4) search for correlations between localized Io Plasma Torus (IPT) brightness and volcanic activity on Io; (5) search for soft X-ray emissions from Jupiter; and (6) determine the long term variability of He 58.4 nm emissions from Jupiter, and relate these to solar variability. However, the ADP review panel suggested that the work concentrate on the Jupiter/IPT observations, and provided half the requested funding. Thus we have performed no work on the first two tasks, and instead concentrated on the last three. In addition we used funds from this project to support reduction and analysis of EUVE observations of Venus. While this was not part of the original statement of work, it is entirely in keeping with extracting important results from EUVE solar system observations.

Gladstone, G. Randall↗
NASA NTRS2002

Long-term Doppler Shift and Line Profile Studies of Planetary Search Target Stars

This grant supported attempts to develop a method for measuring the Doppler shifts of solar-type stars more accurately. The expense of future space borne telescopes to search for solar systems like our own makes it worth trying to improve the relatively inexpensive pre-flight reconnaissance by ground-based telescopes. The concepts developed under this grant contributed to the groundwork for such improvements. They were focused on how to distinguish between extrasolar planets and stellar activity (convection) cycles. To measure the Doppler shift (radial velocity; RV) of the center of mass of a star in the presence of changing convection in the star's photosphere, one can either measure the effect of convection separately from that of the star's motion and subtract its contribution to the apparent RV, or measure the RV in a way that is insensitive to convection. This grant supported investigations into both of these approaches. We explored the use of a Fabry-Perot Etalon HE interferometer and a multichannel Fourier Transform Spectrometer (mFTS), and finished making a 1.8-m telescope operational and potentially available for this work.

McMillan, Robert S.↗
NASA NTRS1977

Unidentified lines in molecular clouds and a search for C-14 in IRC +10216

Two spectral features have been detected toward the Kleinmann-Low infrared nebula in Orion that agree in frequency with the 7(25)-7(16) and 7(35)-7(26) rotational transitions of the ring-structured molecule ethylene oxide (CH2)2O. A feature agreeing in frequency with the 8(24)-8(45) transition probably also was detected; however, seven other transitions in (CH2)2O were not. Additional unidentified lines were detected in Ori A and Sgr B2. Searches for H(C-14)N and (C-14)O in the luminous carbon star IRC +10216 were unsuccessful. However, an unidentified line was found in IRC +10216 that was not detected in the KL nebula.

Kuiper, E. N. R.↗
NASA NTRS2019

An X-Ray Spectroscopic Search For Dark Matter And Unidentified Line Signatures In The Perseus Cluster With Hitomi

The reported detection of a 3.5 keV emission signal in the Perseus cluster core by Bulbulet al. (2014, ApJ, 789, 13) was ruled out at high confidence in analysis conducted by Aharonian et al. (2017, ApJ, 837, L15) of X-ray spectra at 5 eV energy resolution obtained with the Hitomi observatory Soft X-ray Spectrometer (SXS). Using the same data, we search the full 2–12 keV SXS energy band for previously unidentified emission and absorption features. No significant unidentified line emission or absorption is found. Line flux upper limits (1σper resolution element) vary with photon energy and assumed intrinsic width, decreasing from∼100 at 2 keV to<10 photons cm−2s−1sr−1over most of the 5–10 keV energy range for a Gaussian line with Doppler broadening of 640 kms−1. Limits for narrower and broader lines have a similar energy dependence and are systematically smaller and larger, respectively. These line flux limits are used to constrain the decay rate of hypothetical dark matter candidates. For the sterile neutrino decay rate, we place new constraints over the mass range of 4–24 keV with mass resolution better than any previous X-ray analysis. Additionally, the accuracy of relevant thermal spectral models and atomic data are evaluated. The Perseus cluster spectra may be described by a composite of multi-temperature thermal and active galactic nuclei (AGN) power-law continua. Superposed on these, a few line emission signals possibly originating from unmodeled atomic processes (including SiXIV and FeXXV)are marginally detected and tabulated. Comparisons with previous X-ray upper limits and future prospects for dark matter searches using high-energy resolution spectroscopy are discussed.

Takayuki Tamura↗
NASA NTRS1992

High spectral resolution measurement of gamma ray lines from the earth's atmosphere

A search for gamma ray line features from the earth's atmosphere has been conducted using data from the third High Energy Astronomy Observatory (HEAO 3) high spectral resolution gamma ray spectrometer. In addition to the strong line at 0.511 MeV, other intrinsically broadened line features have been observed at 1.63, 2.31, 3.67, 4.43, 5.09, and 6.13 MeV. Since the spectral resolution of the instrument is much finer than the width of the observed line features, the intrinsic width as well as the energy and intensity of each of these lines are reported. Several other predicted lines have also been observed. The characteristic of the lines seen by HEAO 3 are generally consistent with theoretical predictions as well as with previous measurements.

Willet, J. B.↗
NASA NTRS1991

A search for primeval galaxies

We are conducting a search for emission-line objects at large redshifts, ostensibly young and forming galaxies. Our method is to search for strong line emission, in particular Ly-alpha, using two techniques: a direct, narrow-band imaging search using a Fabry-Perot interferometer; and a serendipitous long-slit spectroscopic search. Assuming that none of the faint candidates found so far are actually primeval galaxies, we can set the strongest limits to date on the surface density of Ly-alpha-luminous primeval galaxies on the sky. Some of the faint emission line galaxies detected in our survey at z roughly 0.5 - 1 may be representative of the faint blue galaxy population detected in deep continuum imaging surveys.

Thompson, D. J.↗
NASA NTRS1993

Two searches for primeval galaxies

A number of active galaxies are now known at very large redshifts, some of them even have properties suggestive of galaxies in the process of formation. They commonly show strong Ly-alpha emission, at least some of which appears to be ionized by young stars. Inferred star formation rates are in the range approximately = 100-500 solar mass/yr. An important question is: are there radio-quiet, field counterparts of these systems at comparable redshifts? Whereas, we are probably already observing some evolutionary and formative processes of distant radio galaxies, the ultimate goal is to observe normal galaxies at the epoch when most of their stars form. We have, thus, started a search for emission-line objects at large redshifts, ostensibly young and forming galaxies. Our method is to search for strong line emission (hopefully Ly alpha) employing two techniques: a direct, narrow-band imaging search, using a Fabry-Perot interferometer; and a serendipitous long-slit spectroscopic search.

Thompson, D.↗
NASA NTRS1977

Search for thermal X-ray line emission from the Crab Nebula

Observations of the Crab Nebula from 1.85 to 8 keV obtained with the large-area graphite crystal spectrometer on OSO-8 show a smooth featureless continuum with an absence of X-ray emission lines from highly ionized Si and S. Upper limits on the line emission are used to derive an upper limit to the emission measure for a thermal source associated with the Crab Nebula. Existing evidence for an extended thermal source is discussed, and it is shown that the evidence is not contradicted by the upper limits set with the spectrometer data.

Kestenbaum, H. L.↗
NASA NTRS1978

Search with Copernicus for ultraviolet emission lines in the planetary nebula NGC 3242

The high-excitation planetary nebula NGC 3242 has been observed with the ultraviolet telescope-spectrometer aboard Copernicus. Wavelength intervals corresponding to the emission lines of O VI at 1032 A, He II at 1085 A, Si III at 1206 A, and N V at 1239 A have been scanned. Upper limits to the observed fluxes are reported and compared with predicted emission-line fluxes from this object.

Schwartz, R. D.↗
NASA NTRS1991

Limits to the radiative decay of the axion

An axion with a mass greater than 1 eV should be detectable through its decay into two photons. The astrophysical and cosmological limits which define a small window of allowed axion mass above 3 eV are discussed. A firm upper bound to the axion's mass of M(sub a) less than or equal to 8 eV is derived by considering the effect of decaying axions upon the diffuse extragalactic background radiation and the brightness of the night sky due to axions in the halo of the Milky Way galaxy. The intergalactic light of clusters of galaxies is shown to be an ideal place to search for an emission line arising from the radiative decay of axions. An unsuccessful search for this emission line in three clusters of galaxies is then detailed. Limits to the presence of any intracluster line emission are derived with the result that axions with masses between 3 and 8 eV are excluded by the data, effectively closing this window of axion mass, unless a severe cancellation of axionic decay amplitudes occurs. The intracluster flux limits are then used to constrain the amplitude of any such model dependence.

Ressell, M. Ted↗
NASA NTRS1993

A dwarf galaxy near the sight line to PKS 0454+0356 - A fading 'faint blue galaxy'?

We report the discovery of a dwarf galaxy (MB = -17.2 for H0 = 50 km/s per Mpc) at z = 0.072 which is only 4 arcsec (3.7/h(100) kpc) in projection from the line of sight to the bright quasar PKS 0454+0356 (z(em) = 1.345). The dwarf has very blue optical and optical/IR colors and exhibits line emission indicative of ongoing or recent star formation. However, there is no detection of Ca II 3934 A, 3969 A absorption at z(abs) = 0.072 to equivalent width limits (3 sigma) of about 40 mA, which would suggest an H I column density along the line of sight of less than 5 x 10 exp 19/sq cm, if the Ca II/H I ratio is similar to sight lines in the Galaxy. Based on the absence of Ca II absorption and the unusually weak line emission given the very blue color of the dwarf, we speculate that it may be close to exhausting its supply of gas. As its star formation rate declines, the galaxy's blue magnitude should fade substantially, eventually reaching a quiescent state in accord with its K luminosity of about 0.005 L*. Future observations of the sight line to PKS 0454+0356 using HST in search of Mg II resonance lines, or a search for 21 cm absorption against the quasar radio continuum, could place even more stringent limits on the extent of the gas associated with an intrinsically faint, star-forming dwarf.

Steidel, Charles C.↗
NASA NTRS1997

Gamma ray line observations with OSSE

Observations from the oriented scintillation spectrometer experiment of the gamma ray lines originating from a variety of Galactic center sources are reviewed. Extensive observations were acquired of the Galactic center region, including the 0.511 MeV positron annihilation line and associated positronium continuum and Al-26 emission. The results reviewed include: Co-57 from SN 1987A; limits on Co-56 from SN 1991T; gamma ray lines from solar flares; searches for Ti-44 emission from Cas A, and searches for C-12 and O-16 lines from the Orion region.

Kurfess, J. D.↗
NASA NTRSDate not supplied

New Mission Concept: Compton Telescope with Coded Aperture Mask (GECCO) for MeV Gamma-ray Astronomy

The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO) is a novel Explorer-class concept for a next-generation telescope covering the poorly explored hard X-ray and soft gamma-ray energy regimes. The instrument is based on a novel CdZnTe imaging calorimeter and a deployable coded aperture mask, which enable it to reach 1 arcmin angular resolution and 1% energy resolution. GECCO will connect the arcminute angular resolution observations from X-ray telescopes to high-energy images of the Galactic plane provided by Fermi-LAT, and will focus on the exploration of heavily populated sky regions such as the Galactic Center and the Carina and Cygnus regions to decipher the nature of their emission. These measurements will probe with unprecedented capabilities the possible origin of this emission as dark matter, new types of sources, or currently unresolved populations of point sources. Uncoded observations with GECCO’s Compton telescope will provide wide field-of-view sky monitoring for transient events, synergizing with gravitational wave and high-energy neutrino facilities. In addition, GECCO will conduct a high-sensitivity search for the positron sources in the Galactic Center responsible for the enigmatic 511 keV positron annihilation line excess, will search for as-yet untested candidates for dark matter, will detect and identify high-redshift blazars with excellent angular resolution, and will explore Galactic chemical evolution and sites of explosive element synthesis.

Alexander A Moiseev↗
NASA NTRS1977

The abundance of boron in Vega and Sirius

High-resolution (0.05 A) Copernicus observations of the 1362.46-A B II resonance line in Sirius and Vega are analyzed. In Vega, this line is found to be strong, broad, asymmetric, and blended with another line; it is not observed in Sirius. Angular velocities of 18-20 km/s for Vega and 10 km/s for Sirius are determined. A search for subordinate lines of B II reveals no such features in the Sirius spectrum and the possible weak presence of two unblended lines in that of Vega. The cause of the asymmetry of the B II blend in Vega is investigated, line-profile calculations are performed for Sirius, and the B content of Vega is obtained by means of an LTE synthesis of the B II blend as well as a non-LTE computation of the B II line alone. It is concluded that Sirius is deficient in B relative to Vega by a factor of at least 20. The Be abundances of both stars are also examined in relation to the galactic-cosmic-ray spallation theory for the origin of light elements.

Praderie, F.↗