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At least 1,693 records · Page 94
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NASA NTRS1971

Apollo galactic X-ray astronomy observations

The galactic X-ray observations are a detailed study of the temporal behavior of pulsating X-ray sources. NASA's first X-ray astronomy satellite Uhuru (Explorer 42) has recently discovered fast time variability of pulsations in the output from several sources. The variability occurs on a time scale of minutes, seconds, or less, implying that the emitting regions are very small in size, much smaller than the sun, although they are emitting about a thousand times more power. Fast time variability may provide the clue that is needed to understand the mechanisms which drive pulsating sources. The Apollo observations record the emission from several objects continuously for a period of about an hour. The spacecraft can be pointed at the source for the entire time. On the other hand, Uhuru can observe only for about a minute or two per sighting. Consequently, Apollo has the capability for determining whether periodicities exist in the 10-1000 second range.

Adler, I.↗
NASA NTRS1971

Charge composition of galactic cosmic radiation

Experimental results from the balloon borne ionization spectrometer have enabled the extension of the measurement of the energy spectra of cosmic rays to 10 to the 12th power eV. The exposure factor for this flight was 1825 sq m/sr/sec and approximately 10,000 nuclei with Z greater than or equal to 3 have been observed. Differential spectra of individual nuclei from lithium to oxygen and from groups of nuclei with Z = 10-14, 15-19, 20-23, and 24-30 energy range 2 x 10 to the 10th eV to 10 to the 12th eV are described in a power law representation. Results indicate that the composition of galactic cosmic rays remains similar to that observed at lower energies. These results from direct measurements provide evidence for the processes of source acceleration with interstellar propagation remaining essentially energy independent up to 10 to the 12th power eV.

Ormes, J. F.↗
NASA NTRS1971

A discussion of the H-alpha filamentary nebulae and galactic structure in the Cygnus region

From observation of the galactic structure in Cygnus, the system of filamentary nebulae was found to lie at a distance of roughly 1.5 kpc, in the same region as about half the thermal radio sources in Cygnus X, the supernova remnant near gamma Cygni, and the association Cygnus OB2, in the direction of which the X-ray source Cygnus XR-3 is observed. The source of excitation was probably the pulse of radiation from a supernova explosion, as proposed in the case of Gum nebula. However continuing excitation by early stars in the region of Cygnus X cannot be excluded.

Matthews, T. A.↗
NASA NTRS1971

The spectra of ten galactic X-ray sources in the southern sky

Data on ten galactic X-ray sources were obtained during a rocket flight from Brazil in June 1969. Detailed spectra of these sources have been compared with bremsstrahlung, black body, and power law models, each including interstellar absorption. Six of the sources were fitted well by one or more of these models. In only one case were the data sufficient to distinguish the best model. Three of the sources were not fitted by any of the models, which suggests that more complex emission mechanisms are applicable. A comparison of our results with those of previous investigations provides evidence that five of the sources vary in intensity by a factor of 2 or more, and that three have variable spectra. New or substantially improved positions have been derived for four of the sources observed.

Cruddace, R.↗
NASA NTRS1972

Solar modulation of galactic cosmic rays. 3: Implications of the Compton-Getting coefficient

Spectra of modulated galactic cosmic rays are expressed in terms of the Compton-Getting coefficient C. This parameter can reveal the energy range over which the force field approximation is valid, and the range where convection effects dominate those of diffusion. A value of C near zero over an extended low energy range implies that the radial gradient at low energies can not be large. This small gradient may imply that the diffusion coefficient increases beyond 1 AU less rapidly than proportionally to heliocentric radial distance, and/or there is essentially no scattering for a sizeable distance from the Sun to earth. The behavior of C with rigidity (or energy) is discussed in terms of the omnidirectional distribution function f sub zero. Contours of constant f sub zero in the heliocentric distance vs rigidity plane are useful for illustrating the mean rigidity loss experienced by cosmic rays in the interplanetary medium.

Fisk, L. A.↗
NASA NTRS1972

The modulation of low energy galactic cosmic rays over solar maximum (cycle 20)

A preliminary report is presented on detailed observations of low energy approximately (60 MeV/nucleon) galactic cosmic rays made during the recent period of solar maximum. For this particular cycle a significant time lag between intensity changes in the low energy and high energy components was observed. There are a number of possible explanations of this hysteresis effect. In the simplest form these include either changes in the form of the magnetic field power spectrum or changes in the size of the effective modulating region, or both.

Vanhollebeke, M. A. I.↗
NASA NTRS1972

Diffuse galactic light in the 1500-4200 angstrom region

Diffuse galactic light has been observed with the four stellar photometers of the OAO-2 in 29 of Kapteyn's selected areas. The data can be understood in terms of a wavelength dependent albedo of the interstellar grains with a pronounced minimum around 2200 A with a rapid increase towards unity at wavelengths below 2000 A.

Witt, A. N.↗