X-ray and gamma-ray astronomy at the turning point
X and gamma ray astronomy instrumentation, point sources, continuum emission, line spectra, etc
Peterson, L. E.↗
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Results for “EMISSION SPECTRA”
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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Charged particle emission following pion capture in nuclei
Negative pion capture in nuclei, examining charged particle emission energy spectra
Castleberry, P. J.↗
High-resolution spectra of Io's sodium emission
The shape of Io's sodium D2 emission profile varies markedly with Io's orbital phase, and its width suggests that the sodium cloud may be expanding with velocities up to 18 km/sec. This offers an explanation for at least part of the orbital phase asymmetry observed for the D-line emission.
Trafton, L.↗
The emission-line spectrum above the limb of a solar coronal hole - 1175-1940 A
Emission-line spectra of a coronal hole that coincided with the north pole of the sun are discussed which were obtained with a slit spectrograph aboard Skylab at positions within and above the solar white-light limb in the wavelength range from 1175 to 1940 A. Relative line intensities, line profiles, and full widths at half-maximum are presented for selected chromospheric and transition-zone lines observed above the present polar coronal hole. Average mass motions in the transition zone are determined as a function of electron temperature from the widths of the optically thin lines by assuming ionization equilibrium. The line intensities and profiles are compared with corresponding results deduced from spectra obtained above a quiet solar region. The coronal-hole spectra are found to imply an angular dependence for the source function as well as a radial dependence such that the source function is the smallest at the south pole and increases with decreasing solar latitude.
Feldman, U.↗
CO/d-3 Delta sub i to X-1 Sigma +/ fluorescence from photodissociation of CO2 by 923 A photons
Measurements of vacuum ultraviolet fluorescence from the photodissociation of CO2 by photons from a N IV line emission source at a wavelength of 923 A have revealed a second CO band system in addition to the expected emission bands. Spectra with time resolution were obtained and the fluorescence lifetime and the dependence of fluorescence intensity on CO2 pressure were measured. An analysis of this data has permitted the second band system to be identified as originating from CO(d-3 Delta sub i to X-1 Sigma +) transitions.
Phillips, E.↗
Observed and theoretical profiles of the Si II lines at lambda 1814
Emission line spectra observed at the limb of the solar disc are presented for transitions of singly ionized silicon at lambdas 1816.93, 1817.45 and 1808.01. The profiles show self-reversals in the line cores. A non-LTE analysis for a simplified model of the silicon ion is presented, and calculated line profiles are compared with the observations. The study indicates that some modification of the Vernazza et al. (1973) model of the solar chromosphere in the transition region is needed to reconcile the calculated and observed profiles.
Finn, G. D.↗
A comparison of emission lines in the ultraviolet spectra of Alpha Boo /K2IIIp/, Alpha Tau /K5III/, Alpha Ori /M1-2Ia-b/ and Alpha Sco /M1.5Iab+B2.5V/
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Van Der Hucht, K. A.↗
The optical counterpart of GX 339-4, a possible black hole X-ray source
Optical studies of the galactic X-ray source GX 339-4 (4U 1658-48), which led to its recent identification as reported by Doxsey et al. (1979), are presented. Reddening and distance estimates are given, as well as evidence for optical variability on differing time scales. The emission-line spectra and UBV photometry suggest that GX 339-4 may be at about 8 kpc and have a main-sequence B star binary companion. Both the optical spectrum and optical/X-ray luminosity ratio for GX 339-4 may be similar to Cir X-1.
Grindlay, J. E.↗
Optical redshifts of 59 galaxies
This paper presents the results of an observing program carried out to measure galaxy redshifts with the Cassegrain Digicon Spectrograph system on the McDonald Observatory 2.1 m Struve telescope. New redshift determinations are presented for 59 galaxies, obtained for emission line spectra by conventional wavelength determination techniques and for absorption line spectra by Fourier transform filtering and cross correlation techniques with respect to velocity standard spectra of NGC 3115 and NGC 4736. With respect to published redshifts for 29 galaxies, the new redshifts show a mean residual of -1 km/sec and rms residual of 49 km/sec, without apparent systematic trends, from -300 to +13,700 km/sec.
Kelton, P. W.↗
Densities and mass motions in transition-zone plasmas in solar flares observed from Skylab
The electron densities and bulk motions in the transition-zone plasma of a solar flare are investigated by an analysis of EUV emission line spectra taken on Skylab. Spectra of three flares were obtained with the NRL normal incidence grating slit spectrograph in the ranges 1100-1940 and 1940-3940 A. The line ratios of transition-zone Si III lines and the intensity of the forbidden O IV 1401-A lines during flare maximum indicate electron densities on the order of 10 to the 12th/cu cm, decreasing by a factor of 2 to 3 in the flare decay phase. Line broadening of the transition-zone ions such as Si III, O IV, C IV and N V is noted, and the observed asymmetrical N V line profiles are approximated by a bi-Gaussian model of a stationary and a moving plasma component with a bulk velocity of 12 to 70 km/sec. Turbulent velocities of from 45 to 85 km/sec and from 20 to 40 km/sec are also indicated for the moving and stationary components of the transition-zone plasma, respectively.
Cheng, C.-C.↗
IUE high-dispersion spectrum of R Aquarii
Emission-line spectra of several ions were observed in R Aqr in the wavelength range 1900-3000 A. C II diagnostics gives an electron density of about 400,000/cu cm and an electron temperature of about 10,000 K. The Mg II doublet profiles are grossly asymmetric, of a P Cygni type with terminal ejection velocity of at least 200 km/s. This is like Mg II behavior in Omicron Cet, Zeta Aur, and 32 Cyg, but unlike smaller UV shifts of the Mg II self-absorptions reported so far in other red giants and supergiants.
Johnson, H. M.↗
The remarkable spectrum of some material ejected by Eta Carinae
Some of the outer condensations of the very massive star Eta Carinae have emission-line spectra which convey clues to the nature of the star from which they were ejected. Ground-based spectrograms as well as ultraviolet IUE data on the brightest such condensation is described. Excess nitrogen presumably resulting from the C/N/O cycle implies that the star is at least moderately evolved. The facts seem consistent with recent suggestions that turbulent mixing, combined with mass loss, causes a very massive star like Eta Carinae to evolve quasi-homogeneously.
Davidson, K.↗
Integrated fluxes for emission lines in the ultraviolet spectra of several planetary nebulae
(Previously announced in STAR as N82-13022)
Carpenter, K. G.↗
X-ray and optical studies of emission-line Markarian galaxies
The X-ray and optical properties of a selection of compact nucleus, emission line Markarian galaxies have been studied. Observations with the Einstein Observatory have detected X-rays from all the Seyfert galaxies and none of the narrow emission line galaxies in the sample. This result supports the idea that powerful X-ray emission is correlated with the presence of a broad optical emission line component. The emission line spectra of the Seyfert galaxies show much higher excitation than do the narrow-line galaxies, whose spectra are similar to those of H II regions. Both the optical properties and the radio and X-ray upper limits of the non-Seyfert galaxies are consistent with the suggestion that those objects have undergone bursts of massive star formation.
Ulvestad, J. S.↗
The effects of a multidensity plasma on ultraviolet spectroscopic electron density diagnostics
Spectroscopic electron density diagnostics have been developed for interpretation of UV, EUV, and X-ray emission line spectra of solar and other astrophysical plasmas, and tokamak plasmas. In principle, accurate electron densities can be determined. However, in practice, a number of difficulties arise with respect to the determination of very accurate electron densities in the 1100-3000 A region. The present study has the objective to investigate one of these difficulties, taking into account the effect on line ratios produced by a source composed of several regions of substantially different densities, all at the same temperature. The study is in particular concerned with a source in which small high density knots are embedded in low-density plasma. Attention is given to line ratios involving the O IV multiplet near 1400 A, obtained from the spectrum of a surge observed outside the solar limb.
Doschek, G. A.↗
Search for white dwarf companions of cool stars with peculiar element abundances
A search for a white dwarf companions of cool stars with peculiar element abundances was undertaken. One additional star the xi Cet, was found with a white dwarf companion. It was found that HR 1016, 56Uma, 16 Ser, have high excitation emission lines which indicate a high temperature object in the system. It is suggested that since these indications for high temperature companions were seen for all nearby Ba stars, it is highly probable that all Ba stars have white dwarf companions, and that the peculiar element abundances seen in the Ba stars are due to mass transfer. Observations, arguments and conclusions are presented. White dwarf companions were not found. Together with the Li and Be abundances and the chromospheric emission line spectra in these stars were studied. No white dwarf companions were seen for subgiant CH stars.
Boehm-Vitense, E.↗
Coordinated multifrequency observations of the BL Lacertae objects Mrk 180 and Mrk 501
The continuous spectra of the nearby BL Lac objects Mrk 180 and Mrk 501 have been investigated by making coordinated observations at X-ray, ultraviolet, optical, and radio wavelengths. The observations were planned in order to obtain single-epoch snapshots, or time-frozen spectra, of the emission at many different wavelengths. The spectra were fitted with spherically symmetric, synchrotron self-Compton models and relativistic jet models with relaxed assumptions of spherical geometry and homogeneity and allowance for relativistic motion. It is found that these models provide accurate fits to the observed spectra and tighter constraints on the physical parameters. These models are also not dependent on uncertain source size and synchrotron break frequency.
Mufson, S. L.↗
Review of methodology and technology available for the detection of extrasolar planetary systems
Four approaches exist for the detection of extrasolar planets. According to the only direct method, the planet is imaged at some wavelength in a manner which makes it possible to differentiate its own feeble luminosity (internal energy source plus reflected starlight) from that of the nearby host star. The three indirect methods involve the detection of a planetary mass companion on the basis of the observable effects it has on the host star. A search is conducted regarding the occurrence of regular, periodic changes in the stellar spatial motion (astrometric method) or the velocity of stellar emission line spectra (spectroscopic method) or in the apparent total stellar luminosity (photometric method). Details regarding the approaches employed for implementing the considered methods are discussed.
Tarter, J. C.↗