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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

1 millimeter continuum observations of extragalactic objects

Continuum observations of 23 extragalactic objects have been made at a wavelength of 1 mm; nine of the 23 have been definitely detected at this wavelength. The sources detected include seven from which the 1-mm emission appears to be nonthermal, and two from which the emission appears to be thermal radiation from dust. Repeated observations of the brightest nonthermal sources permitted a search for 1-mm variations on time scales of one month to three years. BL Lac was observed to vary by more than a factor of 2 in flux, and 3C 84, 3C 120, and 3C 273 showed possible variations; 3C 279 showed no variations greater than + or - 30%. The 1-mm variations of BL Lac appear to be correlated with variations at radio wavelengths. The other sources with nonthermal spectra detected were 3C 111 and M87; the two thermal sources detected were NGC 253 and M82. Comparison of the latter two 1-mm measurements with 2.6-mm CO measurements suggests that the CO line in these galaxies is not heavily saturated.

Elias, J. H.↗
NASA NTRS1977

New infrared objects associated with OH masers

Results of a search for IR radiation at 10 microns from a sample of OH maser sources are reported. An IR source is discovered near each of six OH masers which emit mainly at 1612 MHz in two distinct velocity ranges. It is shown that all the sources have varied with time, that two sources have exhibited significant variations in color temperature, and that the energy distributions of the six objects over the spectral range from 2 to 20 microns fall into two categories. Absorption in the 2.3-micron band of CO is detected in two sources, and four are found to display substantial silicate absorption features. The energy distributions of the sources indicate that pumping by 35-micron photons is feasible, but 2.8-micron pumping is very unlikely; the distributions are best explained as emission from very thick dust shells at temperatures of about 500 K. The data are taken as supporting the hypothesis that every double-peaked OH maser emitting principally at 1612 MHz is associated with an IR object. The nature of the objects inside the dust shells and their evolutionary state are briefly discussed.

Evans, N. J., II↗
NASA NTRS1993

A search for radiative neutrino decay from supernovae

Two supernovae have been identified in the COMPTEL data base as being the best sources to investigate for evidence of gamma-ray emission caused by radiative neutrino decay. These are SN1987a and SN1993J. A detailed simulation has shown us that we can expect a gain in sensitivity 1-3 orders of magnitude (depending on neutrino mass) over previous results. Instrument response is now being modeled using a SPARC10 computer acquired for this study. A library of simulated gamma-ray lines is being produced for COMPTEL as a by-product of this effort.

Svoboda, Robert C.↗
NASA NTRS1998

Studying the High Energy Gamma Ray Sky with Gamma Ray Large Area Space Telescope (GLAST)

Building on the success of the Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory, the Gamma Ray Large Area Space Telescope (GLAST) will make a major step in the study of such subjects as blazars, gamma Ray bursts, the search for dark matter, supernova remnants, pulsars, diffuse radiation, and unidentified high energy sources. The instrument will be built on new and mature detector technologies such as silicon strip detectors, low-power low-noise LSI, and a multilevel data acquisition system. GLAST is in the research and development phase, and one full tower (of 25 total) is now being built in collaborating institutes. The prototype tower will be tested thoroughly at Stanford Linear Accelerator Center (SLAC) in the fall of 1999.

Kamae, T.↗
NASA NTRS2018

Direct Laser Ice Penetration System

An optically powered system for rapid, focused heating and melting of water ice. The optical wavelength is chosen to fall in a range where transmissivity through liquid water is higher than through ice. An alternative embodiment of the invention further comprises a length of fiber optic tether between source and output to allow for motion of the melt head. A further embodiment includes probing the ice using various sensing modalities exploiting the presence of the fiber in the ice, searching for biomarkers and characterizing the radiation/light environment for subsurface habitability, including photosynthetic potential and radiation environment as a source for energy.

Hogan, Bartholomew P.↗
NASA NTRS1977

Interpretation of cosmological information on radio sources

The question of whether any cosmological information can be obtained from radio astronomy is considered. Specific attention is given to the discovery and cosmological interpretation of the microwave background radiation, attempts to derive a Hubble relation for the optical objects identified with radio sources, searches for relations between the angular diameters of radio sources and the redshifts of their optically identified counterparts as well as between angular diameter and radio flux, construction of log N - log S curves, and luminosity volume tests. A brief outline is given of the situation that might prevail if a significant population of radio sources is not at great distances and is associated with QSOs that have been ejected from relatively nearby galaxies. It is concluded that: (1) some types of cosmological investigations have been premature; (2) much of the discussion in this area still depends on the distances of QSOs; and (3) there is no conclusive proof that the population of radio sources is changing with epoch.

Burbidge, G.↗
NASA NTRS1993

The terrestrial gravitational wave environment from known sources

The objective of this project was to produce a gravitational wave spectral line list of all known binary stars producing expected strain amplitudes at Earth in excess of h = 10 (exp -21), or gravitational wave fluxes in excess of F = 10 (exp -12) erg cm(exp -2) s(exp -1). These strain and flux limits lie above the anticipated detection thresholds for space-borne laser interferometers capable of detecting gravitational radiation in the 10 micron Hz to 1 Hz frequency range. The source list was intended to provide frequency (including each harmonic), amplitude and phase (for each polarization and harmonic), and celestial coordinates for each system, lacking only the orientation of the principal polarization axis with respect to the pole of the coordinate system, and the sign of the source phase and frequency (or, equivalently, of the sense of rotation of the strain tensor with time) from providing a complete source description. Such a spectral line list would lay essential groundwork for high-sensitivity, low-frequency searches for gravitational radiation.

Webbink, Ronald F.↗
NASA NTRS2003

Stacking Searches for Greater Than 100 MeV Gamma Ray Emission from Radio Galaxies and Seyfert Galaxies

The EGRET telescope on CGRO detected more than sixty sources of high-energy gamma radiation associated with active galactic nuclei (AGN). All but one of those belong to the blazar subclass; the only exception is the nearby radio galaxy Centaurus A. Since there is no obvious reason other than proximity to expect Cen A to be the only non-blazar AGN emitting in high-energy gamma rays, we have utilized the "stacking" technique to search for $>100$-MeV emission from two non-blazar AGN subclasses, radio galaxies and Seyfert galaxies. Maps of gamma-ray counts, exposure, and diffuse background have been created, then co-added in varying numbers based on sorts by redshift, 5-GHZ flux density, and optical brightness, and finally tested for gamma-ray emission. No detection significance greater than $2\sigma$ has been found for any subclass, sorting parameter, or number of objects co-added. Monte Carlo simulations have also been performed, to validate the technique and estimate the significance of the results.

Cillis, A. N.↗
NASA NTRS1992

A liquid xenon imaging telescope for gamma ray astrophysics: Design and expected performance

A high resolution telescope for imaging cosmic x ray sources in the MeV region, with an angular resolution better than 0.5 deg is being developed as balloon-borne payload. The instrument consists of a 3-D liquid xenon TPC as x ray detector, coupled with a coded aperture at a distance of 1 meter. A study of the actual source distribution of the 1.809 MeV line from the decay of Al-26 and the 511 keV positron-electron annihilation line is among the scientific objectives, along with a search for new x ray sources. The telescope design parameters and expected minimum flux sensitivity to line and continuum radiation are presented. The unique capablity of the LXe-TPC as a Compton Polarimeter is also discussed.

Aprile, E.↗
NASA NTRS1975

A survey of carbon monoxide emission in dark clouds

Results are reported of a CO and (C-13)O survey of 68 dark clouds from the Lynds catalog. CO was detected in 63 of the 64 sources in which it was searched for, and the (C-13)O line was seen in 52 of 55 clouds. There is a rather narrow distribution of CO peak line radiation temperatures about a mean of 6 K; this may reflect the presence of a roughly uniform kinetic temperature of 9.5 K in the sources. Despite the probably subthermal excitation temperature of the (C-13)O transition observed, derived (C-13)O column densities are most likely good to within a factor of 2. Typical CO column densities for the clouds surveyed are 5 x 10 to the 17-th power per sq cm, assuming a terrestrial carbon isotope ratio. All 68 clouds have previously been studied by Dieter in 6-cm H2CO absorption; a comparison of line widths shows the (C-13)O lines to generally be wider than their formaldehyde counterparts. Possible explanations of this fact in terms of internal cloud motions are discussed.

Dickman, R. L.↗
NASA NTRS1973

Gamma-ray observations of the galactic centre.

Review of observation data obtained with a portable gas-Cerenkov gamma-ray telescope flown twice from Parana, Argentina (31.8 deg S), to search for gamma radiation from the galactic center. The angular resolution of this detector is not good enough to resolve the source structure controversy, i.e. whether the gamma radiation is coming from point sources or from a diffuse source along the galactic plane. Comparisons with observation data of other investigators are presented and discussed.

Helmken, H. F.↗
NASA NTRS2007

LAT Perspectives in Detection of High Energy Cosmic Ray Electrons

The GLAST Large Area Telescope (LAT) science objectives and capabilities in the detection of high energy electrons in the energy range from 20 GeV to approx. 1 TeV are presented. LAT simulations are used to establish the event selections. It is found that maintaining the efficiency of electron detection at the level of 30% the residual hadron contamination does not exceed 2-3% of the electron flux. LAT should collect approx. ten million of electrons with the energy above 20 GeV for each year of observation. Precise spectral reconstruction with high statistics presents us with a unique opportunity to investigate several important problems such as studying galactic models of IC radiation, revealing the signatures of nearby sources such as high energy cutoff in the electron spectrum, testing the propagation model, and searching for KKDM particles decay through their contribution to the electron spectrum.

Moiseev, Alexander↗
NASA NTRS2003

Strategies for Studying the Sources of Gamma Ray Bursts

The study of gamma ray bursts (GRBs) has rapidly evolved in recent years with the discovery of their cosmological nature and with BATSE, BeppoSAX, HETE and the IPN enabling a wide variety of associated . afterglow measurements. Multiwavelength observations ranging through the radio, optical, soft and hard x-ray, and gamma-ray regimes have exploded the field of GRB interpretation. Also, the Amanda, Milagro and LIGO experiments can search for related neutrino, cosmic-ray photon, and gravitational radiation events, even with the delayed alerts, such as from the IPN. The infrared region, where the optical emissions from sources at the extreme distances may be shifted, will become important but is undersubscribed. The soon-to-be launched Swift mission will greatly broaden the GRB discipline, and a strategy for associated ground-based measurements is outlined. The need for the improved global distribution of all instruments, in particular, robotic infrared detectors, is cited.

Cline, T. L.↗
NASA NTRS1979

New multiple systems in molecular clouds

Twenty-micron searches of the dense cores of the molecular clouds S140, S255, and Cepheus A have revealed the existence of multiple sources of infrared radiation which seem to be precursors to Trapezium-like clusters of OB stars. Two of the new sources are extended with unusually low color temperatures, less than 100 K. Observations with the Very Large Array with 1 mJy sensitivity have shown that three and possibly four of the infrared sources are associated with small H II regions. Multiple systems appear to be the rule rather than the exception in molecular clouds.

Beichman, C. A.↗
NASA NTRS1998

Spacecraft Doppler Tracking as a Narrow-Band Detector of Gravitational Radiation

We discuss a filtering technique for reducing the frequency fluctuations due to the troposphere, ionosphere, and mechanical vibrations of the ground antenna in spacecraft Doppler tracking searches for gravitational radiation. This method takes advantage of the sinusoidal behavior of the transfer function to the Doppler observable of these noise sources, which displays sharp nulls at selected Fourier components.

gravitational radiation doppler tracking↗
NASA NTRS1999

Search for Obscured Nucleus in a Luminous IRAS Galaxy NGC 6240

IRAS discovered very luminous objects which emit the vast majority of their radiation in the infrared wavelength. The energy source of such a tremendous amount of emission is not understood. Starburst and active galactic nuclei (AGN) are thought to be the origin of their power. X-ray observations are expected to be able to reveal the characteristics of the AGN component. However, some are very X-ray quiet, because the AGN is thought to be obscured by a large column density. In order to determine the primary luminosity of the nucleus, we need an X-ray observation with a wide energy band at least up to several tens of keV. We propose to observe NGC 6240, one of the luminous IRAS galaxies, to investigate the characteristics of its AGN, which must be obscured by large column density.

Leighly, Karen↗