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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 1,225 records · Page 68
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NASA NTRS1987

PG 1411 + 442 - The nearest broad absorption line quasar

IUE observations reveal strong, moderately broad absorption troughs in the blue wings of the C IV and N V emission lines of the quasar PG 1411 + 442. No absorption from weakly ionized gas is detected. The emission-line strengths and overall shape of the ultraviolet/optical/near-infrared/far-infrared continuum of the new broad absorption line quasar are within the range normally measured in quasars. Its redshift is low enough to allow the morphology of the host galaxy to be studied in deep broad-band and intermediate-band CCD images. The galaxy appears to be a large spiral with a very long arm or tail. The inclination angle is 57 deg, which rules out the possibility that the line of sight to the nucleus intersects a large path length in a galactic disk.

Malkan, Matthew A.↗
DOE OSTI2024

Detection of the Orbital Modulation of Fe Kα Fluorescence Emission in Centaurus X-3 Using the High-resolution Spectrometer Resolve on board XRISM

Abstract The Fe K α fluorescence line emission in X-ray spectra is a powerful diagnostic tool for various astrophysical objects to reveal the distribution of cold matter around photoionizing sources. The advent of the X-ray microcalorimeter on board the XRISM satellite will bring new constraints on the emission line. We present one of the first such results for the high-mass X-ray binary Centaurus X-3, which is composed of an O-type star and a neutron star (NS). We conducted a 155 ks observation covering an entire binary orbit. A weak Fe K α line was detected in all orbital phases at an equivalent width (EW) of 10–20 eV. We found for the first time that its radial velocity (RV) is sinusoidally modulated by the orbital phase. The RV amplitude is 248 ± 13 km s −1 , which is significantly smaller than the value (391 km s −1 ) expected if the emission is from the NS surface, but is consistent if the emission takes place at the O star surface. We discuss several possibilities of the line production site, including the NS surface, O star surface, O star wind, and accretion stream from the O star to the NS. We ran radiative transfer calculation for some of them assuming spherically symmetric density and velocity profiles and an isotropic distribution of X-ray emission from the NS. None of them explains the observed EW and velocity dispersion dependence on the orbital phase, suggesting that more elaborated modeling is needed. In other words, the present observational results have the capability to constrain deviations from these assumptions.

High energy astrophysics↗
NASA NTRSDate not supplied

Application of EUV and SXR Spectra from the EUNIS Sounding Rocket to Solar Coronal Heating

The nanoflare model is among the most actively investigated approaches to the longstanding problem of solar coronal heating. According to this model, the ~2 MK corona is heated by numerous tiny impulsive heating events, each of which is too small to be detected individually. Evidence for nanoflares is faint emission from small amounts of plasma at flare-like temperatures (4-10 MK) in non-flaring regions. The Extreme Ultraviolet Normal Incidence Spectrograph (EUNIS) sounding rocket instrument was designed to investigate coronal heating by observing emission lines of Fe XVIII, whose maximum ionization fraction occurs at temperatures around 7.1 MK, and Fe XIX (8.9 MK). Although expected to be faint, emission from hot plasma to which these lines are sensitive provides compelling evidence for the nanoflare model. EUNIS observes spectral line emission at 92-115 A in 3rd order, 277-344 A in 1st order, and 530-640 A in 1st order. These wavebands include lines from Fe XVIII and Fe XIX, as well as lines from ions formed over a wide range of lower temperatures (0.1-3.5 MK). We present preliminary results for a quiescent solar active region observed during the flight of 2021 May 18.

ultraviolet radiation↗
NASA NTRS2000

Infrared Spectroscopy of Black Hole Candidates

ISO LWS and SWS observations of the approx. solar mass black hole candidates 1E1740.7-2942 and GRS1758-258 are presented. For 1E1740.7-2942, it has been suggested that the luminosity is provided in whole or part by Bondi-Hoyle accretion from a surrounding black hole (Bally & Leventhal 1991, Nat, 353,234). Maloney et al. (1997, ApJ482, L41) have predicted that detectable far-infrared line emission from [0I] (63 microns), [CII] (158 microns), [SiII] (35 microns) and other lines will arise from black holes which are embedded in molecular clouds. No strong line emission associated with either 1E1740.7-2942 or GRS1758-258 was detected, implying either that 1) these sources are not embedded in dense molecular clouds, or 2) that their average X-ray luminosity over the past 100 years is significantly lower than its current value. The measured upper limits to the line fluxes are compared with the models of Maloney et al.to constrain the properties of the ISM in the vicinity of these X-ray sources.

Colgan, Sean W.↗
NASA NTRS1993

Comparative study of INPIStron and spark gap

An inverse pinch plasma switch, INPIStron, was studied in comparison to a conventional spark gap. The INPIStron is under development for high power switching applications. The INPIStron has an inverse pinch dynamics, opposed to Z-pinch dynamics in the spark gap. The electrical, plasma dynamics and radiative properties of the closing plasmas have been studied. Recently the high-voltage pulse transfer capabilities or both the INPIStron and the spark gap were also compared. The INPIStron with a low impedance Z = 9 ohms transfers 87 percent of an input pulse with a halfwidth of 2 mu s. For the same input pulse the spark gap of Z = 100 ohms transfers 68 percent. Fast framing and streak photography, taken with an TRW image converter camera, was used to observe the discharge uniformity and closing plasma speed in both switches. In order to assess the effects of closing plasmas on erosion of electrode material, emission spectra of two switches were studied with a spectrometer-optical multi channel analyzer (OMA) system. The typical emission spectra of the closing plasmas in the INPIStron and the spark gap showed that there were comparatively weak carbon line emission in 658.7 nm and copper (electrode material) line emissions in the INPIStron, indicating low erosion of materials in the INPIStron.

Han, Kwang S.↗
DOE OSTI2022

Spatially resolved properties of early-type group-dominant galaxies with MUSE: gas content, ionization mechanisms, and metallicity gradients

ABSTRACT With the goal of a thorough investigation of the ionized gas and its origin in early-type group-dominant galaxies, we present archival MUSE data for 18 galaxies from the Complete Local-Volume Groups Sample (CLoGS). These data allowed us to study the spatially resolved warm gas properties, including the morphology of the ionized gas, EW(H α), and kinematics as well as the gas-phase metallicity (12 + log(O/H)) of these systems. In order to distinguish between different ionization mechanisms, we used the emission-line ratios [O iii]/H β and [N ii]/H α in the BPT diagrams and EW(H α). We find that the ionization sources in our sample have variable impacts at different radii; central regions are more influenced by low-luminosity active galactic nuclei, while extended regions of low-ionization nuclear emission-line region-like emission are ionized by other mechanisms with post-asymptotic giant branch stars photoionization likely contributing significantly. We classified our sample into three H α +[N ii] emission morphology types. We calculate the gas-phase metallicity assuming several methods and ionization sources. In general, 12 + log(O/H) decreases with radius from the centre for all galaxies, independently of nebular morphology type, indicating a metallicity gradient in the abundance profiles. Interestingly, the more extended filamentary structures and all extranuclear star-forming regions present shallow metallicity gradients. Within the uncertainties these extended structures can be considered chemically homogeneous. We suggest that group-dominant galaxies in our sample likely acquired their cold gas in the past as a consequence of one or more mechanisms, e.g. gas-clouds or satellite mergers/accretion and/or cooling flows that contribute to the growth of the ionized gas structures.

Lagos, P. (ORCID:0000000223218657)↗
DOE OSTI2026

Early results in the search for extreme coronal line emitters with the Dark Energy Spectroscopic Instrument

Here, we present the results of our search through the early data release (EDR) of the Dark Energy Spectroscopic Instrument (DESI) for extreme coronal line emitters (ECLEs) – a rare classification of galaxies displaying strong, high-ionization iron coronal emission lines within their spectra. With the requirement of a strong X-ray continuum to generate the coronal emission, ECLEs have been linked to both active galactic nuclei (AGNs) and tidal disruption events (TDEs). We focus our search on identifying TDE-linked ECLEs. We identify three such objects within the EDR sample, highlighting DESI’s effectiveness for discovering new nuclear transients, and determine a galaxy-normalized TDE-linked ECLE rate of RG=5 −3+5×10−6 galaxy−1 yr−1 at a median redshift of z=0.2 – broadly consistent with previous work. Additionally, we identify more than 200 AGNs displaying coronal emission lines, which serve as the primary astrophysical contaminants in searches for TDE-related events. We also include an outline of the custom python code developed for this search.

Clark, Peter [Southampton U.; Portsmouth U., ICG] ↗
NASA NTRS1988

A new study of the interacting binary star V356 Sgr

Results on V356 Sgr from IUE and Voyager ultraviolet (500 to 3200 A) observations obtained in 1986 and 1987, primarily during 2 total eclipses are presented. The eclipse of Aug. 15, 1986 was fully covered with IUE low dispersion images and 9 hr of Voyager UVS data. The eclipse of Mar. 25, 1987 was covered with IUE low dispersion images and 1 high dispersion SWP image. During both eclipses the total strength of the emission lines is found to be invariant. An uneclipsed UV continuum is detected at wavelengths shorter than 1500 A. The high dispersion SWP spectrum reveals that the emission lines are extremely broad, almost symmetrical emissions with weak, slightly blue shifted absorption components. No evidence of carbon, C I, C II, C III, or C IV, is seen in the emission or absorption spectrum of V356 Sgr in eclipse. Models for this binary system are presented.

Polidan, R. S.↗
DOE OSTI2026

A New Record Census of Dwarf AGN and a Bimodal $M_{\rm BH}$-$M_{\star}$ Scaling Relation with DESI DR1

Using the first spectroscopic data release from the Dark Energy Spectroscopic Instrument (DESI DR1), we search for AGN signatures in 1,678,787 low-redshift ($0.001 \le z \le 0.45$) line-emitting galaxies. Based on the [NII]-BPT emission-line ratio diagnostic, we identify AGN in 314,245/1,211,573 (25.9%) high-mass ($\log (M_{\star}/M_{\odot}) > 9.5$) and 9648/467,214 (2.1%) dwarf ($\log (M_{\star}/M_{\odot}) \le 9.5$) galaxies. Among these AGN, 17,949 are broad-line candidates (BL-AGN) with broad H$α$ emission, enabling black hole (BH) mass estimates using single-epoch virial methods. We find that the AGN fraction in line-emitting galaxies increases monotonically with stellar mass, rising from $\sim$1.4% at the low-mass end to $\sim$93.3% at the high-mass end. Using the large BL-AGN sample, we extend the $M_{\rm BH} - M_{\star}$ scaling relation down to $\log (M_{\star}/M_{\odot}) \approx 7.8$ and $\log (M_{\rm BH}/M_{\odot}) \approx 4.4$. In the context of high-redshift overmassive BHs, our results suggest that galaxies and their central BHs may follow two distinct evolutionary pathways across cosmic time. With this paper, we release the EmFit value-added catalog, containing emission-line flux and width measurements for $\sim$7.4 million galaxies, the largest catalog with emission-line decomposition into narrow, broad, and outflow components to date. This work significantly expands upon the early DESI results and provides a statistical sample for probing the galaxy$-$BH connection in the low-mass galaxy regime.

Pucha, Ragadeepika [Utah U.; Arizona U., Astron. D↗
NASA NTRS1994

Observation of EX Hydrae with ASCA

We have observed the intermediate polar EX Hya with Advanced Satellite for Cosmology and Astrophysics (ASCA), and have clearly detected He-like and H-like K alpha emission lines from Mg to Fe. The intensity ratios of these pairs of lines are not compatible with an isothermal plasma, and a temperature distribution can no longer be parameterized by the conventional two emission component model. We have successfully decomposed iron line emission into thermal plasma component and flourescent component. The equivalent width of the flourescent component is approximately 80 eV.

Ishida, Manabu↗
NASA NTRS1980

Some implications of ultraviolet observations of quasars and active galaxies

The problem of the order of magnitude discrepancy in the expected and observed ratios of the Lyman and Balmer lines in quasars and active galaxies is reviewed. Whereas early photoionization models for the emission line regions predicted F(L-alpha)/F(H-beta) not less than 40, the observations give values for this ratio in the range 3-8. Attempts at explaining the observations have involved dust, both external and internal to the emission line regions, and improved treatments of the collisional processes and radiative transfer effects in dense (Ne about 10 to the 10th/cu cm), optically thick clouds. None of the effects considered is, by itself, able to explain all the observations, and a combination of several of them is probably required.

Davidsen, A. F.↗
NASA NTRS1993

Powering the superwind in NGC 253

NGC 253 is a prototypical moderate nuclear starburst galaxy. It is a barred SBc spiral galaxy at a distance of approximately 3 Mpc and can be studied on scales down to 15 pc in the optical and near IR. It is a bright IRAS source with a flux of 1000 Jy at 60 microns and a FIR luminosity of 3 x 10(exp 10) solar luminosity. It has a strong Br(gamma) emission line, a signature of ongoing massive star formation and deep CO absorption bands, which are indicative of the dominance of red supergiants in the near IR. It contains a population of compact radio sources, similar to those seen in M82. Optical spectra show that the nucleus is heavily reddened, with a Balmer decrement of approximately 30. NGC 253 possesses a 'superwind,' seen both in x-ray emission and in optical line emission. Nuclear ejection was first suggested to explain the kinematics of the nuclear region. We have obtained J, H, and K images of the entire galaxy at 1.3 arcsec/pixel (18 pc/pixel) using the superconducting quantum interference device (SQUID) on the KPNO 1.3 m. We have constructed a mosaic of 180 s exposures which traces the galaxy over much of its optical extent. The data were shifted, rotated, magnified, and calibrated following normal practice.

Watson, Alan↗
NASA NTRS1971

X-ray spectroscopy of solar active regions and flares.

Review of some recent contributions of X-ray spectroscopy to knowledge about solar active regions and flares. As an example of the importance of X-ray spectroscopy, it is pointed out that, while there are no emission lines from highly ionized silicon in the visible spectrum, the XUV spectrum has emission lines from SiIX through SiXIV. Jordan's (1969) calculations of ionization equilibria for silicon and iron are illustrated by diagrams and discussed. The observation of SiXIV gives evidence for regions having electron temperatures from 5 to 20 million deg. The ability to record the corona against the disk of the sun has enabled Van Speybroeck et al. (1970) to identify many bright diffuse X-ray emitting regions with remnants of old active regions of the type giving rise to unipolar magnetic regions. The physical characteristics of the hot coronal plasma associated with chromospheric flares are outlined on the basis of current observations.

Neupert, W. M.↗
NASA NTRS1980

Two-dimensional photometry of planetary nebulae

Monochromatic images of three planetary nebulae, NGC 6720, NGC 7662 and NGC 2392, were taken using narrow band interference filters centered on the forbidden emission lines of Oxygen I, II, III, Nitrogen II, Sulfur II and the permitted emission lines of Hydrogen I, Helium I and Helium II. The data was taken with a silicon intensified vidicon using the Palomar 1.5 meter telescope and was recorded digitally to an encoding level of 12 bits. The data was processed at the Image Processing Laboratory of the Jet Propulsion Laboratory. The calibrated images were used to investigate the three dimensional structure of the nebulae and to generate two-dimensional electron and temperature maps.

Kupferman, P. N.↗
NASA NTRS1981

Annihilation radiation from a hot e/+/-e/-/ plasma

The radiation from electron-positron annihilations in a plasma of temperature above 10 to the 8th K is investigated as a possible source of the emission line at energies between 400 and 460 keV frequently seen in gamma-ray bursts. The annihilation rate and luminosity of an optically thin electron-positron plasma and the energy distribution of the resulting annihilation radiation are calculated by the use of a Monte Carlo technique as functions of temperature. Results indicate the annihilation spectrum to be peaked at an energy of 0.511 MeV plus a temperature-dependent blueshift, and the annihilation line to be significantly temperature-broadened. The widths of the observed burst emission lines set an upper limit of 3 x 10 to the 8th K on the temperature of any pair annihilation region in burst sources, which is considerably lower than the typical kinetic temperatures of the radiating particles. It is thus inferred that either the annihilation region is nonthermal, or spatially distinct from the burst site.

Ramaty, R.↗
NASA NTRS1989

Ionization by line photons and its effect on hydrogen line ratios

Inside a line-emitting cloud the density of trapped photons could be so high that they ionize hydrogen atoms from excited levels far more efficiently than electronic collisions. Such ionizations can reduce the population of high-level hydrogen and consequently reduce the Balmer line emissivity by a factor of 3 or more. As a result, the Balmer line emission is not enhanced as significantly in the partially ionized zone as predicted by current models unless an exceptionally large column density is assumed.

Zheng, Wei↗
NASA NTRS1995

Phase Determination from Mostly One-sided Interferograms

We show how to detect and correct for non-linear phase shifts in a mainly one-sided interferogram of an emission-line source. We simultaneously detect and correct for an out-of-phase emission background from the spectrometer. The method requires two auxiliary spectra, one of a strong continuum source, and one of an emission-line source with little or no continuum.

Johnson, David G.↗
NASA NTRSDate not supplied

The Experiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)

The EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM) is a high-altitude balloon telescope designed to deepen our understanding of star formation in a cosmological context, shedding light on why the star formation rate declines and breaks away from the cosmological evolution of dark matter for redshifts z>2 [1]. EXCLAIM will operate at 420–540 GHz with a spectral resolution of R=512 to measure the integrated line emission from galaxies and the intergalactic medium (IGM), in particular CO and [CII] line emissions from the nearby universe out to redshifts of z~3.5. This approach is known as Intensity Mapping (IM), which provides efficient access to large cosmological volumes and redshifts with sensitivity limited by detector noise or photon background, while requiring modest apertures. The instrument will employ an array of six superconducting integrated grating-analog spectrometers (µ-Spec) with superconducting microwave kinetic inductance detectors (KIDs) in an all-cryogenic telescope (1.7 K) to achieve near background-limited sensitivity. Here, we present an overview of the EXCLAIM instrument and status, with emphasis on the Attitude Determination & Control System (ADCS) and the thermal system.

Giuseppe Cataldo↗