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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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158 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Galactic-latitude dependence of low-energy diffuse X-rays.

A flux of low-energy diffuse X-rays has been observed which is qualitatively well correlated with 21-cm column densities of hydrogen from intermediate to high galactic latitude. The intensity exceeds that predicted by an extrapolation to low energies of the power-law spectrum observed above 1 keV. The observed X-ray intensity and the apparent correlation with interstellar hydrogen is accounted for by an additional component of extragalactic radiation plus a local component. For the latter, we cannot exclude the possibility that the X-rays are produced in the upper atmosphere. In addition, we have observed a large flux of X-rays near the galactic plane and a prominent feature in the constellation Gemini.

Yentis, D. J.↗
NASA NTRS1972

Search for H-alpha emission from the companion radio sources of Sco X-1.

Attempt to obtain additional evidence linking three companion radio sources to Sco X-1 by the detection of optical emission from possible nebulosity in the region of the X-ray source. Further studies are required to prove that the three sources comprise a single system, since adverse weather conditions prevented needed observations during this attempt.

Vanden Bout, P. A.↗
NASA NTRS1972

Search for coronal line emission from the Cygnus Loop.

The flux from the edges of the Cygnus Loop in the forbidden Fe XIV coronal line at 5303 A is measured to be less than 5 nanoergs per sq cm per sterad per sec (0.017 R) in a 3 A band centered on the line. This upper limit is an order of magnitude lower than the predicted total flux in the line and implies that there must be substantial broadening of the line profile by mass motion or that the temperature is somewhat higher than the present best estimate from X-ray data.

Kurtz, D. W.↗
NASA NTRS1973

Spectroscopic observations of HZ Herculis. II

Preliminary results from an extensive series of spectroscopic observations of the HZ Her optical counterpart of the eclipsing, pulsating X-ray binary Her X-1. Spectrograms with a dispersion of 30 A/mm reveal a spectral type as late as F5 near minimum in the light curve with the G-band and metallic lines present. Narrow Fe lines show that HZ Her is not a rapid rotator. Low-dispersion (115 A/mm) spectra, obtained with 10-minute time resolution, reveal rapid (10-min) variations in the 4640 N III emission and in the 4471 He I absorbtion features. The H-beta absorption is variable in equivalent width, and shows evidence of being partially filled with emission.

Bopp, B. W.↗
NASA NTRS1974

Nonperiodic optical flickering in HZ Herculis

High-speed simultaneous dual-channel photometry of HZ Her and a nearby comparison star reveal nonperiodic optical flickering in the HZ Her system on a time scale of 15 to 300 sec. The amplitude of the flickering appears to be correlated with orbital phase. Optical emission from a hot spot in a disk of material around the X-ray source cannot account for the flickering.

Moffett, T. J.↗
NASA NTRS1978

The energetics of molecular clouds. II - The S140 molecular cloud

Techniques of analysis which allow estimates of kinetic temperature, gas density, gas cooling rate, and dust cooling rate are applied to the S140 molecular cloud. Maps of this cloud in various molecular lines are examined which reveal the existence of a strong temperature and density peak near the H-alpha rim and the presence of a strong near-IR source very near that peak. This source is found to have an energy distribution which is very similar to that of the Becklin-Neugebauer object, including the silicate feature at 9.5 microns. The heating and cooling rates for the gas and dust in S140 are estimated, and the predicted cooling rate for dust is shown to be much greater than that for gas. The molecular-line observations are compared with a spherical large-velocity-gradient trapping calculation. An optimum cloud model is developed which indicates that: (1) (C-13)O, HCO(+), and H2CO are about 10 times less abundant in S140 than in dark clouds; (2) the HCN abundance is approximately 4 times the H2CO abundance in S140, compared with roughly equal values in dark clouds; and (3) the (C-13)O/C(O-18) ratio is consistent with terrestrial isotope ratios.

Blair, G. N.↗
NASA NTRS1978

Further observations of nonperiodic optical flickering in HZ Herculis

High-speed photometric observations of the HZ Her/Her X-1 system show that nonperiodic optical flickering is present during both the ON and OFF portions of the 35-day cycle. The optical flickering is broad band and not confined to emission lines. There is a weak correlation between the amplitude of the flickering and orbital phase but efforts to identify the source of the flickering were unsuccessful.

Vanden Bout, P. A.↗
NASA NTRS1981

The energetics of molecular clouds. IV - The S88 molecular cloud

The S88 molecular cloud has been observed in several molecular lines and at infrared wavelengths from 1 to 100 microns. The CO emission has a single, sharp peak which is near the H-alpha emission region S88 B and centered on a compact H II region observed in the radio continuum. The infrared observations indicate that the principal luminosity source is located near the radio continuum peak and is hidden behind substantial extinction, presumably from the molecular cloud. The molecular cloud has a size of about 6.5 pc and a mass of about 5,000 solar masses at an assumed distance of 2 kpc. Regions of very high density (more than 10,000/cu cm) do not seem to be present. Analysis of the energetics leads to a predicted dust cooling rate in good agreement with the infrared observations, which indicate L = 180,000 solar luminosities. A more detailed examination of the energetics indicates that densities may be insufficient for collisions of molecules with warm dust grains to heat the gas to the observed kinetic temperature.

Evans, N. J., II↗
NASA NTRS1982

The energetics of molecular clouds. V - The S37 molecular cloud

The molecular clouds of S37, which coincides with a region of visual obscuration, is observed at several molecular transition frequencies and at IR wavelengths in the 2-125 micron range. It is found that the temperature and the column density peak near the reflection nebulae vdB 118 and 119, with line splitting and possible self-absorption being observed near the latter. Although many 2-micron sources are observed in the direction of the cloud, no bright, 10-micron sources are seen, and far-IR emission is found over an extensive region in the cloud. An energetics analysis leads to the prediction of a dust cooling rate consistent with the far-IR observations, which indicate not less than 15,000-35,000 solar luminosities, and more detailed energetics examinations show that the conditions necessary for collision heating of the gas by warm dust exist.

Evans, N. J., II↗
NASA NTRS1994

IRAS F15307+3252: A hyperluminous infrared galaxy at z = 0.93

A new hyperluminous infrared galaxy in the Infrared Astronomy Satellite (IRAS) Faint Source Catalog is identified at a redshift of 0.93. This object has a bolometric luminosity of approximately 10(exp 13) solar luminosity, a very large ratio of infrared-to-optical luminosity, warm dust emission, a ratio of infrared-to-radio flux densities consistent with other infrared galaxies, and an optical spectrum similar to a Seyfert 2 galaxy. IRAS F15307+3552 shares these characteristics and its radio-to-optical spectral energy distribution with two other infrared galaxies, F10214+4724 and P09104+4109. Discovery of a third object with these properties defines an extreme subclass of ultraluminous galaxies powered primarily by star formation. The systematic method used to find this object begins the process of determining the space density of these most luminous examples of the infrared galaxy phenomenon.

Cutri, Roc M.↗