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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

On the optical identification of Cygnus X-1

Bright star at radio source and X ray observations evaluation from optical identification of Cygnus X-1, taking into account spectrum and energy distribution characteristics

Brucato, R.↗
NASA NTRS1971

Further observations of the pulsating X-ray source Cygnus X-1 from Uhuru.

Since the discovery of the pulsations from the X-ray source Cygnus X-1 more data from Uhuru have been analyzed. The conclusions reached about the temporal behavior of the source are described. Large fluctuations of intensity exist on all observed time scales ranging from 50 msec to 10 sec containing up to 50 per cent of the power. Periodic pulse trains with periods from 0.3 sec to over 10 sec exist containing 10-25 per cent of the power; however, they persist only for several seconds or several tens of seconds. No single period is consistently present. This behavior is shown to reconcile the apparently contradictory results obtained by other observers. The energy spectrum of the source is best fitted by a power law, but with great variability in the spectral index and with an excess of flux at higher energies.

Schreier, E.↗
NASA NTRS1971

X-ray observation of a new soft source in Cygnus.

The location of the new X-ray source, designated Cygnus X-6, is discussed. The polycarbonate window counter detected Cyg X-6 only in the pulse-height interval from 0.5 to 1.3 keV. A total of 44 counts was acquired from the source above a diffuse X-ray and non-X-ray background of 18 plus or minus 3 counts. The polycarbonate pulse-height spectrum for Cyg X-6 is presented together with the calculated counter response to three different model source spectra.

Coleman, P. L.↗
NASA NTRS1971

X-ray structure of the Cygnus Loop.

X-ray emission from the Cygnus Loop was observed in the energy region around 0.2 to 1 keV with a collector that focused X-rays along one dimension while scanning across the nebula. The total integrated intensity is 13 nanoerg per square centimeter per second. The one-dimensional X-ray structure has the same angular size - about 3 degrees - as the outermost boundaries of the optical filaments. There is no increase in X-ray emission at the center of the nebula nor at the strong feature that is seen in certain radio maps. The X-ray spectrum is consistent with thermal radiation from a hot plasma at a temperature of about 4 million K.

Gorenstein, P.↗
NASA NTRS1972

Low energy X-ray survey from the Crab Nebula to Cygnus.

Observations of cosmic X-rays in the energy band 0.2-3.0 keV were made from an experiment on board an Aerobee 170 rocket launched from White Sands, N.M. on Dec. 19, 1970. A survey along the galactic plane between the Crab Nebula and Cygnus provided data on the interstellar absorption and X-ray flux for the Crab Nebula, NP 0532, Cas A, and Cyg X-2; upper limits were obtained for the flux from a number of supernova remnants. The 1/4 keV X-ray background was measured over a limited range of galactic latitude and longitude.

Garmire, G.↗
NASA NTRS1972

Observations of Cygnus X-3 by Uhuru.

Report on the X-ray intensity observations of Cygnus X-3 performed with the aid of the X-ray satellite, Uhuru, before and during the radio flare of early September 1972. An analysis of 32 transits of the source, obtained during the period August 19 to September 6, is presented. There is no indication of an intensity change coincident with the radio flare. It is concluded that whatever precipitated the radio flare did not have a significant impact on the X-ray emitting region. Other characteristics of Cyg X-3 are also discussed.

Parsignault, D. R.↗
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

The X-ray surface brightness of the Cygnus Loop.

The surface brightness of the Cygnus Loop in X rays was obtained on a scale of 0.25 sq deg. The X-ray emission shows strong limb brightening, implying a shell-like source structure. The shell exhibits several regions of enhanced emission. X-ray emission which was observed from a region near the center of the Loop may be from a remnant object. The correlation between X-ray and optical emission is not as good as the correlation between radio and optical emission.

Stevens, J. C.↗