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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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NASA NTRS1971

The UV spectrum of the Crab Nebula

Observations of the Crab nebula are described, which were made under the OAO 2/NASA guest-investigator program with WEP stellar photometers. The 10 foot-diameter focal plane diaphragm was ample enough to accept the 4 ft X 6 ft image. The logarithm of the integrated relative intensity per wavelength interval, corrected for sky background, and the rms error, from 11 passbands in the range 4250 to 1380 A, are given. No correction was given for polarization of light. The data were converted to logarithm of the flux density per frequency interval and plotted on scales of log nu (Hz) and of reciprocal microns with two adjustments.

Johnson, H. M.↗
NASA NTRS1972

Discovery of interstellar circular polarization in the direction of the Crab Nebula.

A search in many small regions of the Crab Nebula has resulted in the detection of a small component of circular polarization. The variation of the sign and magnitude with position in the Nebula indicates that the polarization is of interstellar origin. On the basis of the polarity, strength, and colour dependence, it is concluded that the composition of the aligned grains causing this polarization is dielectric. Metallic particles are clearly ruled out. Some stars have also been observed with negative results.

Martin, P. G.↗
NASA NTRS1973

VLBI observations of the Crab Nebula pulsar.

Observations of the Crab Nebula pulsar at meter wavelengths using very long baseline interferometry techniques have been made. At 196.5 MHz, no resolution of the pulsar is observed, all the pulse shapes observed with the interferometers are similar to single-dish profiles, and all the power pulsates. At 111.5 MHz, in addition to the pulsing power, there is always a steady component, presumably due to multipath propagation effects. The pulsar is slightly resolved at 111.5 MHz with an apparent angular diameter of 0.07 plus or minus 0.01 sec. Fifty per cent linear polarization of the time-averaged power is observed at 196.5 MHz; at 111.5 MHz, 20% of the total time-averaged power is polarized, and 35% of the pulsing power is polarized. The steady component is unpolarized. The total flux of the steady plus pulsating component appears to remain constant, while the distribution of power between these components varies.

Vandenberg, N. R.↗
NASA NTRS1972

The 1969 solar occultation of the Crab Nebula pulsar.

Results of an occultation experiment carried out on June 14-15, 1969, when the Crab Nebula pulsar passed within 80 min of arc from the center of the sun. For a time interval of two months around this event comparisons are made of the reception times of pulses at frequencies of 111.5, 196.5, and 430 MHz for the purpose of determining the contribution of the solar corona to the integrated electron density along the total path length to the pulsar. For impact parameters between 5 and 12 solar radii the measured integrated densities are not incompatible with those that can be derived from a spherically symmetric Baumbach-Allen model. The systematic differences in density obtained at each observation frequency can be explained in terms of refraction effects.

Rankin, J. M.↗