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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
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Detection of the 1400 A absorption in the ultraviolet spectrum of the DA white dwarf LB 3303

Low-resolution ultraviolet International Ultraviolet Explorer spectra of the southern white dwarf LB 3303 show the presence of the wavelength 1400 absorption feature reported by Greenstein in the spectrum of 40 Eri B. The equivalent width is 5.7 A, and the measured wavelength is 1394 A. A comparison of the ultraviolet fluxes with model atmospheres confirms that LB 3303 has an effective temperature near 16,000 K, as found earlier from visual wavelength data. There are still problems with the identification of this line. The star is not hot enough to explain the presence of Si IV, and the agreement with the spectrum of the H2 molecule is not convincing.

Wegner, G.↗
DOE OSTI2025

Erratum: “Tripling the Census of Dwarf AGN Candidates Using DESI Early Data” (2025, ApJ, 982, 10)

We identified an error in the EmFit code, which was employed to estimate the emission-line fluxes and widths used in the published article. Specifically, the error spectrum was not corrected for Galactic reddening before being incorporated into the fitting process. Although this does not affect the measured fluxes or line widths, it led to underestimated uncertainties. Consequently, the signal-to-noise ratios (SNRs) for individual sources were systematically overestimated, resulting in a larger number of sources satisfying a given SNR threshold.

Pucha, Ragadeepika [University of Utah, Salt Lake ↗
NASA NTRS1980

Hercules X-1 hard X-ray pulsations observed from HEAO 1

The 1.24-sec pulsations of Her X-1 in the energy range 13-75 keV have been analyzed in data obtained from the UCSD/MIT experiment on HEAO 1 during observations of the source on three dates in February 1978 and three in August 1978. Observational results are (1) the main pulse broadens somewhat with increasing energy; (2) the pulsation light curve undergoes pronounced changes at the leading edge of the main pulse from day to day; (3) spectral hardening within the main pulse is confirmed; (4) a 40-60 keV spectral feature in the spectrum is confirmed; (5) this feature is resolved, the pulse width broadening is greater than 20%, and its centroid varies with pulsation phase; and (6) the 13-75 keV spectrum does not noticeably vary from day to day, except for an overall intensity factor. Some implications of these results for the prevailing models of Her X-1 and the HZ Her-Her X-1 system are briefly discussed.

Gruber, D. E.↗
NASA NTRS1981

A 5.57 hour modulation of the X-ray flux of 4U1822-37: A new model for CYG X-3

The X-ray flux of 4U1822-37 is shown to be modulated with the 5.57 hour period of its optical counterpart. The X-ray light curve is two component with a smooth sinusoidal like 25 percent semiamplitude modulation and a 30 minute dip approximately 0.2 in phase following the other minimum. The X-ray spectrum is a relatively flat power law up to 17 keV, above which its steepens. Iron emission is detected at 6.7 keV with a 4 keV FWHM and an equivalent width of 1100 eV. There is an excee below 2 keV that is consistent with either a 0.25 keV thermal component or 350 eV equivalent width iron L emission. A slight softening of the spectrum is seen during both X-ray minima. The dip is interpreted as the partial occultation of an extended cloud of optically thick highly ionized material surrounding the central X-ray source. Modeling the eclipse gives a system inclination of 70-79 deg and a spherical cloud radius of 0.2-0.3 solar radius. Models for the long term modulation are considered. The properties of this source are compared to those of Cyg X-3. It is concluded that they are similar systems.

White, N. E.↗
DOE OSTI2020

Interface structures of inclined ZnO thin film on (0 1 1)-MgO substrate with bulk-like optical properties

Combining different phase structure materials with unique properties to design novel devices plays a significant role in the development of modern electronics. Here, we explore the characteristics of this type of complex interface and epitaxy structures based on the coupling between hexagonal ZnO film and cubic MgO substrate. The ZnO film was prepared by the molecular beam epitaxy technique on the MgO (0 1 1) substrate. The analysis results from the in situ reflection high energy electron diffraction patterns, X-ray diffraction (XRD)-pole figures and high resolution transmission electron microscopy images demonstrate that the film exhibits two-fold symmetry domains with a growth direction deviated from c-axis at about 31º along the [0 1 0] MgO or [0 $\bar{1}$ 0] MgO azimuth. Despite the intertwined diffusion from Zn and Mg atoms in the interface, which is the possible origin of a blue shift of about 0.083 eV in the Photoluminescence (PL) spectrum, the inclined film shows a full width at half maximum value that is close to the reported value from the high quality film. Finally, this work hopefully provides useful insights to the design and exploration of the novel optoelectronic devices that involve the integration of materials with different structure and different properties.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Development of digital electronics for the search of SHE nuclei using GARIS-II/III at RIKEN

This work describes the implementation of a digital data acquisition system for the search and study of short-lived isotopes or superheavy elements at the GARIS-III separator at the RIKEN Nishina Center. Here a reduction to 26 ± 0.5 keV in the average value of the Full Width at Half Maximum of the alpha spectrum at 7.133 MeV was achieved, combined with a reduction of the dead time of the overall system to around a few tens of nanoseconds for the detection of very fast decay chains. Moreover, we measured a reduction of the background induced by particles crossing the implantation detector using pulse shape analysis techniques. The detail of the optimization and analysis will be presented.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
NASA NTRS1978

The clouds of Venus - An anisotropic scattering model

The phase function for anisotropic scattering is applied to a homogeneous atmospheric model to ascertain the effects of anisotropy on the near-infrared spectrum of Venus. Young's (1971) equivalent widths for the 7820-A CO2 band are analyzed to derive allowed combinations of CO2 specific abundance, continuum albedo, pressure, and degree of anisotropy. From these combinations, values are derived for the photon mean free path and total optical thickness of the clouds. The Venera 10 measurement of the transmitted flux at 7200 A is then used in conjunction with spherical-albedo requirements to reduce the range of possible solutions to the equivalent-width analysis. Through the application of approximate similarity relations, the 'true' (i.e., anisotropic) atmospheric parameters are derived from the isotropic values. For an assumed Mie scatterer with an average anisotropy factor of 0.7, the results indicate a total optical thickness of about 55 with a single-scattering albedo of 0.9992 to 0.9995.

Lestrade, J. P.↗
NASA NTRS1979

The annihilation of galactic positrons

The annihilation of galactic positrons is studied in order to evaluate the probabilities of various channels of annihilation and to calculate the spectrum of the resulting radiation. The narrow width (FWHM less than 3.2 keV) of the 0.511-MeV line observed from the galactic center by Leventhal, McCallum, and Stang (1978) implies that a large fraction of positrons should annihilate in a medium of temperature less than 100,000 K and ionization fraction greater than 0.05. H II regions at the galactic center could be possible sites of annihilation.

Bussard, R. W.↗
NASA NTRS1979

Optical studies of the Seyfert 2 X-ray galaxy NGC 2110

Spectrophotometry of the nucleus of the X-ray galaxy NGC2110 shows a typical Seyfert Type 2 spectrum with a strong galactic continuum. The widths of the forbidden lines are about 360 km/s (FWHM), H-beta being somewhat broader. The moderate Balmer decrement implies that the interstellar reddening is approximately 2.1 mag. The average electron density and temperature in the line-emitting region are approximately 300 per cu cm and 35,000 K, respectively. From measurements of the nebulium line, it is found that the extent of the nucleus measured along the major axis of the galaxy is about 10 arcsec (2100 pc) and the full range of gas velocities is about 700 km/s. A direct plate is discussed which shows faint spirallike features in NGC2110, a galaxy currently classified as elliptical. NGC2110 is a member of a new class (about 5 members) of very nearby (cz less than 2500 km/s) X-ray galaxies. Bradt et al. (1978) tentatively concluded that they are Seyfert Type 2 galaxies. This conclusion is supported, and it is shown that this is not inconsistent with the narrowness (less than 500 km/s FWHM) of their emission line.

Mcclintock, J. E.↗
NASA NTRS1983

Iron and magnesium in the white dwarf GD 40 - A test of diffusion theory

An outstanding problem in interpreting the properties of white-dwarf stars is related to the understanding of the chemical abundances in their atmospheres. The hydrogen-rich white-dwarf stars have monoelemental atmospheres, with small quantities of helium and no heavier elements observed in most, possibly all, stars with visible H lines. The helium-rich stars are more complex, and the existence of metallic lines in many of their spectra is now well confirmed. The DB star GD 40 (Gr 384) is the hottest He-rich white-dwarf star to show metal lines, apart from the extremely hot objects, such as HZ 21 and HD 149499B. The present investigation is concerned with IUE spectra which have been obtained of the GD 40. It is found that the near-UV is marked by strong Mg II lines along with broad blends of Fe II lines. An analysis is conducted of the abundances of Fe and Mg at the surface of GD 40 using a limited spectrum-synthesis technique with the measured equivalent widths of the best Fe II features.

Shipman, H. L.↗
NASA NTRS1984

Helium 10830 Angstrom Irradiance: 1975-1983

A fairly complete time series from late 1974 to mid-1983 is available of values of the equivalent width of the He I 10830A chromospheric spectrum line averaged over the visible solar disk. Variation from about 25 mA in 1975 to about 80 mA in late 1981 is the major component of the signal. The 10830 variation reaches minimum about a year before the sunspot minimum and reaches maximum about a year after sunspot maximum. Superposed on the solar cycle variation is a modulation of up to + or - 13 mAdu to the passage of active regions across the disk. Power spectral analysis of the time series shows a major peak at a synodic rotation period of 27.42 days and smaller peaks at 1/2, 1/4 and 1/6 of this period. The spectrum is well modeled by a basic fluctuating component with an exponentially decaying autocovariance function of scale time of 43 days. Analysis of the data indicates that the rotational modulation occurs in episodes that last from 4 to 10 rotations. These episodes arise when active regions tend to occur in a limited longitude range. The analysis also shows that the apparent rotation period increased from 1977 to 1981. The apparent rotation period since 1981 is markedly shorter.

Harvey, J. W.↗
NASA NTRS1987

Nine optically selected quasars with redshifts larger than 3

The detection of nine quasars with redshifts between 3.0 and 3.8 is reported. The quasars were all found in a grism survey from their Lyman-alpha emission line. The r magnitudes of the quasars range from 18.5 to 21.7. The strengths of the Lyman-alpha lines are comparable to the values observed in other quasars (rest equivalent widths from 40 to 160 A). The spectrum of one of the objects possesses complex broad absorption features, similar to those seen in PHL 5200. A preliminary evaluation of these findings suggests that the comoving quasar density declines gradually beyond z = 3.

Schmidt, Maarten↗
NASA NTRS1995

Ultraviolet to optical spectral distributions of northern star-forming galaxies

We report spectral energy distribution from the UV to the optical for a sample of 31 northern star-forming galaxies. We also present measurements for emission-line fluxes, continuum levels, and equivalent widths of absorption features for each individual spectrum as well as averages for the eight galactic activity classes, including normal, starburst, Seyfert 2, blue compact dwarf, blue compact, Low-Inonization Nuclear Emission Regions (LINER), H II, and combination LINER-H II galaxies.

Mcquade, Kerry↗
NASA NTRS1999

Relativistic Electrons Observed at UARS and the Interpretation of their Storm-Associated Intensity Variations

The High Energy Particle Spectrometer (HEPS) instrument on the Upper Atmosphere Research Satellite (UARS) provides a database of electron intensities well resolved in energy and pitch-angle. Because of its 57 deg. orbital inclination, UARS encounters with magnetic shells L greater than 2 occur quite far off-equator (B/B (sub 0) greater than 9), corresponding to equatorial pitch angle alpha (sub 0) greater than 20 deg. Data acquired by HEPS (October 1991 through September 1994) span the declining phase of Solar Cycle 22. To reveal the storm-associated time dependence of relativistic electron intensities over the wide range of energies (50 keV to 5 MeV) covered by HEPS, we divide the daily average of the measured spectrum at a given L value (bin width = 0.25) by the corresponding 500-day average and plot the results with a color scale that spans only 2.5 decades. The data show that our off-equatorial electron intensities typically increase with time after the end of recovery phase (not during main phase or recovery phase) of each geomagnetic storm. The delay in off-equatorial energetic electron response and the subsequent lifetime of the corresponding electron flux enhancement seem to increase with particle energy above 300 keV. The trend below 300 keV seems to be opposite, such that the delay varies inversely with electron energy. Our working hypothesis for interpretation is that stormtime radial transport tends to increase the phase-space densities of trapped relativistic electrons but typically leads to a flux increases at specified energies only as the current (as indicated by Dst) decays. Flux enhancements in early recovery phase are greatest for equatorially mirroring electrons, and to pitch-angle anisotropies are initially large. Subsequent pitch-angle diffusion broadens the flux enhancement to particles that mirror off equator, thus gradually increasing low-altitude electron intensities (as detected by HEPS/UARS) on time scales equal to about 20% of corresponding lifetimes against diffusion into the loss cone. Alternative interpretations will also be examined.

Pesnell, W. D.↗
NASA NTRS2002

Impact of MIE-Resonances on the Atmospheric Absorption of Water Clouds

Clouds strongly modulate radiative transfer processes in the Earth's atmosphere. Studies, which simulate bulk properties of clouds, such as absorption, require methods that accurately account for multiple scattering among individual cloud particles. Multiple scattering processes are well described by MIE-theory, if interacting particles have a spherical shape. This is a good assumption for water droplets. Thus, simulations for water clouds (especially for interactions with solar radiation) usually apply readily available MIE-codes. The presence of different drop-sizes, however, necessitates repetitive calculations for many sizes. The usual representation by a few sizes is likely to miss contributions from densely distributed, sharp resonances. Despite their usually narrow width, integrated over the entire size-spectrum of a cloud droplet distribution, the impact of missed resonances could add up. The consideration of these resonances tends to increase cloud extinction and cloud absorption. This mechanism for a larger (than by MIE-methods predicted) solar absorption has the potential to explain observational evidence of larger than predicted cloud absorption at solar wavelengths. The presentation will address the absorption impact of added resonances for typical properties of water clouds (e.g. drop size distributions, drop concentrations and cloud geometry). Special attention will be given to scenarios with observational evidence of law than simulated solar absorption; particularly if simultaneous measurements of cloud micro- and macrophysical properties are available.

Wiscombe, W.↗
NASA NTRS1985

New calorimetric all-particle energy spectrum

Both the maximum size N sub m and the sea level muon size N sub mu have been used separately to find the all-particle energy spectrum in the air shower domain. However the conversion required, whether from N sub m to E or from N sub mu to E, has customarily been carried out by means of calculations based on an assumed cascase model. It is shown here that by combining present data on N sub m and N sub mu spectra with data on: (1); the energy spectrum of air shower muons and (2) the average width of the electron profile, one can obtain empirical values of the N sub m to E and N sub mu to E conversion factors, and an empirical calorimetric all-particle spectrum, in the energy range 2 x 10 to the 6th power E 2 x 10 to the 9th power GeV.

Linsley, J.↗
DOE OSTI2022

Tracing the outflow kinematics in Type 2 active galactic nuclei

Here, we used a sample of 577 spectra of active galactic nuclei Type 1.8-2 (z < 0.25) taken from the Sloan Digital Sky Survey to trace the influence of the outflow kinematics on the profiles of different emission lines (Hβ, [O III], Hα, [N II], [S II]). All considered lines were fitted with two Gaussian components: one that fits the core of the line, and another that fits the wings. We provide a procedure for decomposition of the Hα+[N II] wavelength band for spectra where these lines overlap. The influence of the gravitational and non-gravitational kinematics on the line components is investigated by comparing the dispersions of the line components with stellar velocity dispersion. We find that wing components of all the considered emission lines have pure non-gravitational kinematics. The core components are consistent with gravitational kinematics for the Hα, [N II], and [S II] lines, while in the [O III] there is evidence for contribution from non-gravitational kinematics. We adopted the wing components as a proxy for the outflow contribution and investigated the outflow kinematics by analysing the correlations between the widths and shifts of the wing components of different lines. For this purpose, we used the subsets in which wing components are detected in both compared lines, and can be fitted independently. We find strong correlations between wing component shifts, as well as between wing component widths of all considered lines, with the exception of the Hβ wing component width. These correlations indicate that outflow dynamics systemically affect all emission lines in the spectrum. However, it reflects with a different strength in their profiles, which is observed as different widths of the wing components. This is investigated by comparison of the mean widths of the wing components in subsets where wing components are present in all lines. The strongest outflow signature is observed in the [O III] lines, which have the broadest wing components; weaker outflow signatures are found in Hα and [N II], and the weakest is found for [S II]. These results imply that the considered lines arise in different parts of an outflowing region.

79 ASTRONOMY AND ASTROPHYSICS↗