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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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

New X-ray and optical observations of the X-ray discovered QSO-galaxy pair 1E 0104.2 + 3153

New X-ray and optical observations are presented of the QSO-galaxy pair 1E 0104.2 + 3153, originally discovered as a serendipitous source in the Einstein Observatory Medium Sensitivity Survey (Gioia et al., 1984). Results from an extremely deep Exosat observation are used to suggest that the QSO rather than the compact group of galaxies is the optical counterpart of the IPC source. High-resolution (1-A) spectroscopy of the broad-absorption-line QSO, which fails to confirm the Ca II H and K absorption features reported by Stocke et al., (1984), is presented and discussed. The presence of broad absorption lines in the QSO spectrum may indicate that intrinsic absorption is the cause of the nondetection of this source in the soft Exosat energy band. Optical monitoring of the QSO over a 2-yr period indicates variability. Possible interpretations of this phenomenon are intrinsic luminosity variation or a cessation of a gravitational lensing effect acting at the time of the Einstein observation.

Gioia, I. M.↗
NASA NTRS1986

The Medium Sensitivity Survey and the X-ray selected quasar sample

Statistical investigations of X-ray-emitting quasars are reviewed, focusing on the possible incompleteness of the Einstein IPC Medium Sensitivity Survey (MSS) (Maccacaro et al., 1982; Stocke et al., 1983; Gioia et al., 1984). The criteria used in constructing the MSS and calculating the source parameters are discussed, and the corrections determined for each line of sight by Maccacaro and Gioia (1986) on the basis of the H I measurements of Stark et al. (1986) are shown to have no effect on the completeness of the MSS extragalactic sample as a whole and of the quasar sample in particular. Other possible reasons for inconsistencies between the MSS sample and optically selected quasar samples are considered; ongoing efforts to expand the MSS sample are described; and some preliminary results are presented in graphs.

Gioia, Isabella M.↗
NASA NTRS1990

Probing the Interstellar Medium of External Galaxies Using Quasar Absorption Lines: the 3C 232/NGC 3067 System

Quasar absorption lines offer unique opportunities to probe the interstellar medium of external galaxies. Researchers present new optical and UV absorption line spectroscopy of the quasar 3C232 (z=0.55) revealing new detail in the foreground absorption system due to the bright, spiral galaxy NGC 3067 (cz=1420 km/s). Specifically, the spectra show evidence for two and possibly three separate absorption components in CaII and Na I spanning approx. 150 km/s. The original HI detection of Haschick and Burke (1975) corresponds to the strongest of these metal systems which exhibits doublet ratios consistent with saturation in both CaII and Na I. Due to the recent detection in HI emission of a tidal tail or finger of HI extending from the western edge of NGC 3067 through the position of 3C 232 (Carilli, van Gorkom and Stocke, 1989), the morphology of the HI absorber is now known and is not either a warped disk nor a spherical halo as had been proposed. New deep continuum and H alpha imaging provides a sensitive upper limit on the the ionizing continuum impinging upon this cloud (and thus a limit on the intensity of the extragalactic ionizing radiation field). Together with the observed UV spectrum of 3C 232, the optical emission line ratios and the deep H alpha imaging set a minimum distance between the quasar and the HI cloud disregarding redshift information. This limit strains the non-cosmological redshift interpretation for 3C 232 -- and this quasar is one of the original 5 3C quasars found to be too close to NGC galaxies as if by chance (Burbidge, Burbidge, Solomon and Strittmatter, 1972).

Stocke, John T.↗
NASA NTRS1992

Discovery of neutral hydrogen 21 centimeter absorption at redshift 0.25 toward PKS 1413+135

A strong H I 21-cm absorption line is identified toward PKS 1413+135 at the redshift of the host galaxy and argued to indicate that the IR-optical cutoff of the BL Lac object's spectrum is caused by extinction. The BL Lac object is shown to have strong neutral 21-cm absorption at the redshift range z = 0.24671 +/- 0.00001, and the implied H I column density is derived. The H I covering factor is assumed to be not more than 0.1, suggesting that a high degree of extinction exists in the galaxy. The host galaxy is theorized to be a spiral of type later than S0 based on the redshift of the H I absorption line and the host. The statistical and observational conclusions are found to support the theories of Stock et al. (1992) regarding the red spectrum of the object.

Carilli, C. L.↗
NASA NTRS1993

The new BL Lacertae objects discovered by an efficient X-ray/radio/optical technique

We report the recent discovery of ten BL Lac objects in the Einstein IPC Slew Survey by means of X-ray/radio versus X-ray/optical color-color diagrams and confirming optical spectroscopy. These ten BL Lac objects were discovered using a technique proposed by Stocke et al. (1989) which exploits the characteristic broad-band spectra of BL Lac objects. New VLA detections provide accurate fluxes (limiting f(6 cm) about 0.5 mJy) and about 1 arcsec positions, facilitating the determination of an optical counterpart. All ten new BL Lac objects show essentially featureless optical spectra and lie within the range of radio/X-ray/optical colors of known X-ray-selected BL Lac objects, when about 1 mag optical variability is included. We expect about 50 new BL Lac objects in total, from complete optical follow-up of our now completed VLA work and recent Australia Telescope observations, yielding a complete Slew Survey sample of about 90 BL Lac objects.

Schachter, Jonathan F.↗
NASA NTRS1996

Intergalactic Hydrogen Clouds at Low Redshift: Connections to Voids and Dwarf Galaxies

We provide new post-COSTAR data on one sightline (Mrk 421) and updated data from another (I Zw 1) from our Hubble Space Telescope (HST) survey of intergalactic Ly(alpha) clouds located along sightlines to four bright quasars passing through well-mapped galaxy voids (16000 km/s pathlength) and superclusters (18000 km/s). We report two more definite detections of low-redshift Ly(alpha) clouds in voids: one at 3047 km/s (heliocentric) toward Mrk 421 and a second just beyond the Local Supercluster at 2861 km/s toward I Zw 1, confirming our earlier discovery of Ly(alpha) absorption clouds in voids (Stocke et al., ApJ, 451, 24). We have now identified ten definite and one probable low-redshift neutral hydrogen absorption clouds toward four targets, a frequency of approximately one absorber every 3400 km/s above 10(exp 12.7/sq cm column density. Of these ten absorption systems, three lie within voids; the probable absorber also lies in a void. Thus, the tendency of Ly(alpha) absorbers to 'avoid the voids' is not as clear as we found previously. If the Ly(alpha) clouds are approximated as homogeneous spheres of 100 kpc radius, their masses are approximately 10(exp 9)solar mass (about 0.01 times that of bright L* galaxies) and they are 40 times more numerous, comparable to the density of dwarf galaxies and of low-mass halos in numerical CDM simulations. The Ly(alpha) clouds contribute a fraction Omega(sub cl)approximately equals 0.003/h(sub 75) to the closure density of the universe, comparable to that of luminous matter. These clouds probably require a substantial amount of nonbaryonic dark matter for gravitational binding. They may represent extended haloes of low-mass protogalaxies which have not experienced significant star formation or low-mass dwarf galaxies whose star formation ceased long ago, but blew out significant gaseous material.

Shull, J. Michael↗
NASA NTRS2023

Tree Growth Enhancement Drives a Persistent Biomass Gain in Unmanaged Temperate Forests

While enhanced tree growth over the last decades has been reported in forests across the globe, it remains unclear whether it drives persistent biomass increases of forest stands, particularly in mature forests. Enhanced tree growth and stand-level biomass are often linked with a simultaneous increase in density-driven mortality and a reduction in tree longevity. Identifying empirical evidence regarding the balance between these processes is challenging due to the confounding effects of stand history, management, and environmental changes. Here, we investigate the link between growth and biomass via the negative relationship between average tree size and stand density (tree number per area). We find increasing stand density for a given mean tree size in unmanaged closed-canopy forests in Switzerland over the past six decades and a positive relationship between tree growth and stand density across forest plots—qualitatively consistent with our simulations using a mechanistic, cohort-resolving ecosystem model (BiomeE). Model simulations show that, in the absence of other disturbances, enhanced tree growth persistently increases biomass stocks despite simultaneous decreases in carbon residence time and tree longevity. However, the magnitude of simulated biomass changes for a given growth enhancement critically depends on the shape of the mortality functions. Our analyses reconcile reports of growth-induced reductions of tree longevity with model predictions of persistent biomass increases, and with our finding of trends toward denser forests in response to growth—also in mature stands.

biomass stocks↗
NASA NTRS1962

METEOROLOGICAL SATELLITES

This paper presents a status report on the progress of the Meteorological Satellite Program. In this review, I shall try to emphasize primarily the accomplishments since May 1961 when a report on the program was given to the First National Conference on Peaceful Uses of Space in Tulsa, Oklahoma. It is now one year later, and it is fitting that we stop and take stock of what we have been doing and where we are heading.

Meteorological satellite↗
NASA NTRS1965

Spiral heater coils hand-formed with fixture

Bench model jig and fixture used for hand fabricating spiral coils of various lengths from flat strip stock. This tool is used to make springs and coils to custom lengths.

Chattin, J. H.↗
NASA NTRS1966

Electrical upsetting of metal sheet forms weld edge

Electric gathering of sheet stock edges forms metal sheets in the shape of gore sections with heavier edge areas that can be welded without loss of strength. The edges are gathered by progressive resistance heating and upsetting, and are formed automatically. This process avoids disturbance of the metals internal structure.

Scherba, E. S.↗
NASA NTRS1966

Large seals fabricated from small segments reduce procurement lead time

Large diameter seals are fabricated from narrow strip stock welded in segments to form a complete ring. This technique could be used to reduce the cost of critical, large diameter seals in the heating and ventilating industry, petrochemical industry, and marine fabrication industry.

Daniels, C. M.↗
NASA NTRS1968

Cure of epoxy resins determined by simple tests

Rapid visual and simple quantitative tests indicate the degree of cure of particular epoxy resin binders in prepreg stock. It is possible that these tests may be extended to a number of different epoxy formulations.

Ladaki, M.↗
NASA NTRS1968

Thread cutting with 3-axis N/C milling machine

TAPDIE, a generalized macro written for the APT numerical control system, cuts threads in stock too big for conventional machines or for which conventional methods are unsuitable. TAPDIE computes the machine tool path necessary and the information is passed on to a post-processor which produces a control tape.

Salley, G. C.↗
NASA NTRS1968

Remote sensing of fishery resources

Investigating feasibility of locating, identifying and quantifying surface and near-surface fish stocks from aircraft and spacecraft

Drennan, K. L.↗