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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Iron K Lines from Accretion Disks: Models for Line Production and Spectroscopic Constraints

Measured profiles of the iron K lines provide important dynamical information about emitting matrial in compact objects. However, much of the modeling work which has been used to infer the location and origin of line observed from AGN and galactic black hole sources is based on highly simplified assumptions about the microphysics of K line emission. In particular, many of the intrinsic line energies, widths and emissivities are based on central-field atomic calculations. We present the results of new calculations of the quantities for the entire iron isonuclear sequence, and demonstrate that the intrinsic K line spectra contain considerably more complexity than has been previously considered. We also present calculations of iron K emission and absorption spectra which include the new data, including the local spectrum radiated from an X-ray illuminated accretion disk. The implications for the interpretation of observed iron K lines from black hole sources will be discussed.

Kallman, Timothy↗
NASA NTRS2005

Atom Resonance Lines for Modeling Atmosphere: Studies of Pressure-Broadening of Alkali Atom Resonance Lines for Modeling Atmospheres of Extrasolar Giant Planets and Brown Dwarfs

We report on progress made in a joint program of theoretical and experimental research to study the line-broadening of alkali atom resonance lines due to collisions with species such as helium and molecular hydrogen. Accurate knowledge of the line profiles of Na and K as a function of temperature and pressure will allow such lines to serve as valuable diagnostics of the atmospheres of brown dwarfs and extra-solar giant planets. A new experimental apparatus has been designed, built and tested over the past year, and we are poised to begin collecting data on the first system of interest, the potassium resonance lines perturbed by collisions with helium. On the theoretical front, calculations of line-broadening due to sodium collisions with helium are nearly complete, using accurate molecular potential energy curves and transition moments just recently computed for this system. In addition we have completed calculations of the three relevant potential energy curves and associated transition moments for K - He, using the MOLPRO quantum chemistry codes. Currently, calculations of the potential surfaces describing K-H2 are in progress.

Hasan, Hashima↗
NASA NTRS2023

The J and K Dependencies of the Line Coupling and Line Mixing Effects: Theoretical Studies of the Relaxation Matrices of N 2 -Broadened Ch 3 D

Line coupling and line mixing effects in parallel and perpendicular bands of CH 3 D perturbed by N 2 have been studied. The work focuses on exhibiting the j and k dependencies of these two processes. The calculations were based on a previously reported anisotropic intermolecular potential including both the long-range multipole, induction, and dispersion forces and a short-range atom-atom model. It is shown that components with L 1 = 3 of the atom-atom model are dominant contributions to the diffusion operator. As a consequence, in comparison with other molecular systems such as the CH 3 Cl-N 2 and CH 3 I-N 2 , theoretically predicted line coupling and line mixing effects exhibit completely new j and k dependencies. In general, the theoretically calculated halfwidths and intra-doublets’ off-diagonal elements of the relaxation matrix are in reasonable agreement with measurements.

Methane-d↗
DOE OSTI2025

XRISM Constraints on Unidentified X-Ray Emission Lines, Including the 3.5 keV Line, in the Stacked Spectrum of 10 Galaxy Clusters

We stack 3.75 Ms of early XRISM Resolve observations of 10 galaxy clusters to search for unidentified spectral lines in the E = 2.5–15 keV band (rest frame), including the E = 3.5 keV line reported in earlier low spectral resolution studies of cluster samples. Such an emission line may originate from the decay of the sterile neutrino, a warm dark matter (DM) candidate. No unidentified lines are detected in our stacked cluster spectrum, with the 3σ upper limit on the m s ∼ 7.1 keV DM particle decay rate (which corresponds to an E = 3.55 keV emission line) of Γ ∼ 1.0 × 10 −27 s −1 . This upper limit is 3–4 times lower than the one derived by Hitomi Collaboration from the Perseus observation but still 5 times higher than the XMM-Newton detection reported by E. Bulbul et al. in the stacked cluster sample. XRISM Resolve, with its high spectral resolution but small field of view, may reach the sensitivity needed to test the XMM-Newton cluster sample detection by combining several years worth of future cluster observations.

Astronomy and AstroPhysics↗
NASA NTRS1987

A computer code to calculate line by line atmospheric transmission spectra on a microcomputer

A computer program is described which calculates line by line atmospheric transmission spectra on a microcomputer. Radiance calculations are not included. The program is written in FORTRAN and could be modified to run on a microcomputer other than the one on which it was implemented, except that the plotting routine would have to be replaced. The program is based on the 1978 Air Force Geophysics Laboratory LASER routine, and uses absorption line data from the 1982 update of the AFGL Atmospheric Absorption Line Parameters Compilation; segments of needed line data are taken from the tape, preprocessed into the form used by the program and stored on floppy disks. The program calculates transmission spectra over a variety of paths and spanning an arbitrarily chosen wavelength or frequency range; the path may be chosen to be horizontal, vertical or slanted at any zenith angle, and may extend between any two altitudes between 0 and 15 km. Aerosol effects are included, presently based on the 1976 Shettle and Fenn models, plus some molecular continuum effects and Rayleigh scattering.

Safren, H. G.↗
NASA NTRS1987

Emission-line variability and the broad-line region of quasi-stellar objects. I - Time scales and photon densities

Spectroscopic data for five low-redshift QSOs taken over several years are presented as evidence for emission-line variability in QSOs. The broad hydrogen emission lines in the QSOs 0026 + 129, 1202 + 281, 1612 + 261, and 2141 + 175 are found to vary in step with their underlying continua. Another QSO, 2135 - 147, shows an increase in the intensities of its hydrogen lines five years after the increase in its continuum level. The inferred upper limit to the size of the broad emission line region is smaller than 3 lt-yr, probably as small as 0.4 lt-yr for 0026 + 129, if the line-emitting region is spherically distributed. Such a small size implies a very high density of ionizing photons, of the order of 10 to the 10th/cu cm. A very high nucleon density must then be assumed in order to obtain a value of the ionization parameter consistent with current photoionization models.

Zheng, Wei↗
NASA NTRS1991

Compton backscattered 511 keV annihilation line emission and the 170 keV line from the Galactic center direction

It is shown that Compton scattering of 511 keV electron-positron annihilation radiation produces a linelike reflection feature at 170 keV from backscattered photons. Assuming simple models of clouds and accretion disks around a compact source, the paper explores the spectrum of Compton-scattered annihilation line emission for a range of geometries, opacities, and observing angles, and finds that the linelike feature is produced under a wide variety of conditions. It is further shown that such Compton backscattering of slightly redshifted annihilation line emission from the inner edge of an accretion disk could account for the 170 keV line emission and higher energy continuum observed together with the 511 keV annihilation radiation from the direction of the Galactic center. Identification of the observed 170 keV line as a slightly redshifted annihilation line reflection feature provides strong new evidence that the source of this emission is a compact object surrounded by a disk of presumably accreting matter.

Lingenfelter, Richard E.↗
NASA NTRS1992

Numerical simulation and analysis of a prefrontal squall line. I - Observations and basic simulation results. II - Propagation of the squall line as an internal gravity wave

Results of an observational and numerical study of the squall line that occurred on June 17-18, 1978, are presented. This squall line was initially triggered by the strong surface convergence along a cold front and stretched from Illinois to the Texas Panhandle. The squall line was aligned with the surface front during its initial development, but then propagated faster than the front, resulting in a separation of approximately 200 km by 0300 UTC and 300-400 km by 0600 UTC. The Colorado State University Regional Atmospheric Modeling System is used to model the squall-line development and propagation. Results are described from several experiments that tested the sensitivity to the use of the Kuo-type cumulus parameterization scheme and grid-scale microphysical processes. The movement of the squall line in the model is shown to be due to the propagation of a deep tropospheric internal gravity wave in a CISK-like process. The thermal and dynamic perturbations associated with the hypothesized wave are shown to be consistent with internal gravity wave theory.

Cram, Jennifer M.↗
NASA NTRS1992

The formation of helioseismology lines. III - Partial redistribution effects in weak solar resonance lines

This paper investigates the formation of the Na I D2, K I 769.9 nm and Ba II 455.4 nm resonance lines in the solar atmosphere allowing for partial frequency redistribution (PRD). We show that the influence of PRD is negligible on the solar disk in all three lines for a model of the average quiet-Sun, and even for the more extreme case of a model with a steeper photospheric temperature decline. At the solar limb PRD does affect the intensity profile of the Na I and Ba II resonance lines, but not that of the K I line. Finally, we find that effects of PRD are more pronounced at the limb in the Na I D2 and Ba II 455.4 nm lines when the photospheric temperature gradient is steep.

Uitenbroek, H.↗
NASA NTRS1994

Emergence of double-peaked emission lines in the broad-line radio galaxy Pictor A

A new optical spectrum of the nearby broad-line radio galaxy (BLRG) Pictor A reveals a prominent double-peaked component of the Balmer lines which does not appear in any historical spectra of this object. Carried out with the hope of obtaining exactly such a result, this observation is a key to the interpretation of double-peaked emitters. If bolsters our previous conclusion that there is a set of additional properties which are associated with the rare class of double-peaked emitters, namely F-R II radio morphology, strong low-ionization forbidden lines, weak UV continuum, and flat far-infrared spectrum. Furthermore, the low-velocity, 'ordinary' broad Balmer lines in Pictor A remained relatively unchanged as the new twin peaks appeared, which justifies the practice of applying models that fit only the double peaks and not the low-velocity components that are often present in spectra of this type. We discuss the relative merits of accretion-disk models and other models for double-peaked emission lines in the light of this new observation.

Halpern, Jules P.↗
NASA NTRS1996

The Hubble Space Telescope Quasar Absorption Line Key Project: The Unusual Absorption-Line System in the Spectrum of PG 2302+029--Ejected or Intervening?

We report the discovery of a high-ionization broad absorption line system at a redshift of z(sub abs) = 0.695 in the spectrum of the z(sub em) = 1.052 radio-quiet quasar PG 2302+029. Broad absorption with FWHM from 3000 to 5000 km/s is detected from C iv, N v, and O vi in Hubble Space Telescope (HST) Faint Object Spectrograph spectra of the quasar. A narrow-line system (FWHM approx. 250 km/s) at z(sub abs) = 0.7016 is resolved from the broad blend and includes absorption by Ly alpha and the C iv, N v, and O vi doublets. No absorption by low-ionization metal species (e.g., Si II and Mg II) is detected in the HST or ground-based spectra for either the broad or the narrow system. The centroids of the broad system lines are displaced by approx. 56,000 km/s to the blue of the quasar's broad emission lines. The reddest extent of the broad-line absorption is more than 50,000 km/s from the quasar. The properties of this system are unprecedented, whether it is an intervening or an ejected system.

Jannuzi, B. T.↗
NASA NTRS2004

An Extreme, Blueshifted Iron Line in the Narrow Line Seyfert 1 PG 1402+261

We report on a short, XMM-Newton observation of the radio-quiet Narrow Line Seyfert 1 PG 1402+261. The EPIC X-ray spectrum of PG 1402+261 shows a strong excess of counts between 6 - 9 keV in the rest frame. This feature can be modeled by an unusually strong (equivalent width 2 keV) and very broad energy at 7.3 keV appears blue-shifted with respect to the iron Kalpha emission band between 6.4 - 6.97 keV, whilst the blue-wing of the line extends to 9 keV in the quasar rest frame. The line profile can be fitted by reflection from the inner accretion disk, but an inclination angle of greater than 60 degrees is required to model the extreme blue-wing of the line. Furthermore the extreme strength of the line requires a geometry whereby the hard X-ray emission from PG1402+261 above 2 keV is dominated by the pure-reflection component from the disk, whilst little or none of the direct hard power-law is observed. Alternatively the spectrum above 2 keV may instead be explained by an ionized absorber, if the column density is sufficiently high (NH greater than 3 x 10(exp 23) per square centimeter) and if the matter is ionized enough to produce a deep (tau approximately equal to 1) iron K-shell absorption edge at 9 keV. This absorber could originate in a large column density, high velocity outflow, perhaps similar to those which appear to be observed in several other high accretion rate AGN. Further observations, especially at higher spectral resolution, are required to distinguish between the accretion disk reflection or outflow scenarios.

Reeves, J. N.↗
NASA NTRS2020

Line shape parameters of PH3 transitions: Theoretical studies of self-broadened widths and line mixing effects

Line mixing effects have been calculated in various parallel and perpendicular bands of self-broadened PH3 lines and compared with recent experimental data. The theoretical approach is an extension to symmetric tops with high inversion barrier of the formalism previously developed for NH3 [Q. Ma and C. Boulet, J. Chem. Phys. 144, 224303 (2016)]. The model takes into account the non-diagonality of the scattering operator within the line space as well as, in a correct way, the double degeneracy of the j, k levels when k ≠ 0. Transitions between such levels should be considered as doublets whose components may be coupled by the line mixing process. It has been shown that, at low pressure, the inversion of the experimental data will strongly depend on the splitting between the two components of a doublet. When it is significant, one can measure independently both the width of one component and the intra-doublet coupling matrix element. Otherwise, one can only measure the sum of these two elements. Comparisons with measurements show that the present formalism leads to accurate predictions of the experimental line shapes.

Remote sensing↗
DOE OSTI2024

Understanding Line Losses and Transformer Losses in Rural Isolated Distribution Systems

Rural, isolated power systems in the mainland U.S. and in states like Alaska and Hawaii are powered by assets like diesel generators. These rural, isolated power systems also cannot operate at the higher band of medium voltage (like 69kV). They are primarily in the 12 to 14 kV range to keep the cost of the distribution investments lower. Because of this mid-band medium voltage range, the line losses and distribution transformers losses consume significant diesel consumption (almost 10 percent of the peak load). This work considers one such power system powering an isolated system and presents key findings online losses, and transformer losses. Understanding and documenting the impacts is critical for these communities operating their power systems and take actions to reduce expensive diesel consumption. In this paper, we will present one such typical grid and model it in electromagnetic transients (EMT) domain. We used the tower structure, under ground cabling installation to develop high fidelity models of lines. We also used high fidelity models of distribution transformers to present the no-load losses and full load loses. We will also present technical solutions available commercially off-the-shelf to reduce these losses and reduce diesel consumption. This work will be a primer for communities to understand the technical challenges and to understand the possible solution available to solve such challenges for rural, isolated power system operators.

blackstart↗
DOE OSTI2026

Pre-commissioning of the wide-dynamic range halo monitor to be installed in the Fermilab MI-8 line

The beam halo can contribute to beam losses in accelerators and is very difficult to measure. With an increase in beam intensity following the PIP-II upgrade at Fermilab, the beam losses are expected to be higher with some coming from beam halo. Therefore, it is important to measure the sources of beam halo to minimize the beam losses. A modified Halo Monitor developed by J-PARC will be installed in Fermilab MI-8 transfer line to measure the beam halo. In this paper, an update on the beam profile monitor fabrication is covered. The updates include the location selection for the Halo Monitor in the MI-8 transfer line, shielding options for instrumentation, initial testing of equipment, and ray tracing simulations for the Offner optics and the targets used in the monitor.

Babacan, Betiay [IIT, Chicago; Fermilab]↗
DOE OSTI2026

Current status of the electron transport line from RCS to ESR: RTE line

The electron injection system of the U.S. Electron-Ion Collider (EIC) is located outside of the RHIC tunnel. Electrons beams accelerated by the Rapid Cycling Synchrotron (RCS) must be transported to the Electron Storage Ring (ESR), which resides within the RHIC tunnel. To accomplish this, a dedicated beam transport line, referred to as RTE (RCS-to-ESR) line is being designed. The proposed conceptual design comprises three main sections; RCS extraction, a vertical bend and dispersion suppression region, and ESR injection matching. The extraction section uses pulsed kickers and septum magnets to achieve a total deflection angle of 3 degrees. To align the injection section with ESR, the beamline must provide a vertical elevation of 1.68 m, and an array of FODO cells is used to suppress the vertical dispersion. The total length of the RTE line is approximately 133 m, and this paper presents the current design status and considerations for this transport line.

Accelerator Physics↗
NASA NTRS1974

Suspension-line wave motion during the lines-first parachute unfurling process

A new mathematical approach to modeling the lines-first parachute unfurling process is presented. The unfurling process is treated as two distinct phases: a suspension-line unfurling phase, during which a massless-spring model of the suspension-line elasticity may be employed; and a canopy unfurling phase, during which a formulation considering suspension-line wave mechanics is employed. Histories of unfurled length and tension at the vehicle obtained using the model are compared with flight test data, and generally good agreement is observed.

Poole, L. R.↗
NASA NTRS1978

Line formation in the solar chromosphere. I - The C II resonance lines observed with OSO 8

The temperature structure of the upper chromosphere is investigated using center-to-limb measurements of the C II resonance lines at 1335 A from the University of Colorado spectrometer aboard OSO 8. Spectrum synthesis of these lines shows them to be extremely sensitive to the temperature and the physical extent of the 20,000 K plateau proposed by Vernazza et al (1973). Hydrostatic equilibrium models of the quiet chromosphere are computed to obtain theoretical spectra of the Lyman lines and continuum as well as the center-to-limb behavior of the C II lines. Good agreement is found with observations for a plateau at 16,500 K with about 25% more material than that of Vernazza et al.

Lites, B. W.↗