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  • 1
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    Cosmic X-ray observations with OSO-8 (1976)
    In:  CASI
    Details
    Publication Date: 2006-01-12
    Description: The GSFC Cosmic X-ray Spectroscopy experiment aboard OSO-8 has operated successfully since launch providing spectral and temporal data on X-ray sources in tha energy range 2-60 keV. Analysis of quick look data shows a variety of spectral features, some stable, others variable, which will increase understanding of the nature of individual sources. In particular, observed emission and absorption features that can be attributed to iron will result in abundance measures of this important element in sources such as some X-ray binaries, the supernova remnant Cas A, and the nucleus of the galaxy Cen A.
    Keywords: SPACE RADIATION
    Type: X-ray Binaries; p 67-79
    Format: text
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  • 2
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    A 5.57 hour modulation of the X-ray flux of 4U1822-37: A new model for CYG X-3 (1981)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The X-ray flux of 4U1822-37 is shown to be modulated with the 5.57 hour period of its optical counterpart. The X-ray light curve is two component with a smooth sinusoidal like 25 percent semiamplitude modulation and a 30 minute dip approximately 0.2 in phase following the other minimum. The X-ray spectrum is a relatively flat power law up to 17 keV, above which its steepens. Iron emission is detected at 6.7 keV with a 4 keV FWHM and an equivalent width of 1100 eV. There is an excee below 2 keV that is consistent with either a 0.25 keV thermal component or 350 eV equivalent width iron L emission. A slight softening of the spectrum is seen during both X-ray minima. The dip is interpreted as the partial occultation of an extended cloud of optically thick highly ionized material surrounding the central X-ray source. Modeling the eclipse gives a system inclination of 70-79 deg and a spherical cloud radius of 0.2-0.3 solar radius. Models for the long term modulation are considered. The properties of this source are compared to those of Cyg X-3. It is concluded that they are similar systems.
    Keywords: SPACE RADIATION
    Type: NASA-TM-82079
    Format: application/pdf
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  • 3
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    X-ray spectrum of Kepler's SNR (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Observations made with the solid state spectrometer aboard the Einstein Observatory confirm Kepler's SNR as an X-ray source with an intensity between 1-3 KeV of 7.2 x 10 to the-11th power ergs/sq cm-s. The X-ray spectrum is similar to those of Cas A and Tycho, with strong line emission from the helium-like species of Si, S, and Ar. Direct comparisons to Tycho's SNR suggest a distance of Kepler's SNR of greater than or equal to 5 kpc.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80637
    Format: application/pdf
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  • 4
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    Is the remnant of SN1006 crab-like? (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The solid state spectrometer on the Einstein Observatory and the GSFC cosmic X-ray spectrometer on OSO-8 observed the X-ray spectrum of SN1006. The data can be well-represented by a power-law model with alpha = 1.2, similar to the spectrum of the Crab nebula. This is in contrast to the radio and X-ray maps of SN1006 which show a shell structure more typical of SNR with thermal X-ray emission. The X-ray spectrum is suggestive of nonthermal synchrotron emission, raising the possibility that the remnant of SN1006 contains a source of relativistic electrons.
    Keywords: SPACE RADIATION
    Type: NASA-TM-80689
    Format: application/pdf
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  • 5
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    The electron spectra in the synchrotron nebula of the supernova remnant G 29.7-0.3 (1985)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: EXOSAT results obtained with the imaging instrument (CMA) and the medium energy proportional counters (ME) are discussed. Assuming that the featureless power-law spectrum obtained in the 2 to 10 keV range is synchrotron radiation from relativistic electrons, one derives constraints on magnetic field strength and age of the nebula. The energy spectra of the electrons responsible for the emission in the radio and X-ray ranges are discussed. The great similarity of the physical properties of G 29.7-0.3 and of three synchrotron nebulae containing a compact object observed to pulse in X-rays makes G 29.7 - 0.3 a very promising candidate for further search for pulsed emission. Further observations at infrared wavelengths might reveal the break(s) in the emitted spectrum expected from the radio and X-ray power-law indices and give us more information on the production of the electron populations responsible for the emission of the nebula.
    Keywords: SPACE RADIATION
    Type: OG-6.2-10 , 19th Intern. Cosmic Ray Conf - Vol. 2; p 394-397; NASA-CP-2376-VOL-2
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  • 6
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    Spectral evolution of a long X-ray burst (1976)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: An X-ray burst-like event with a peak intensity 1 1/2 times that of the Crab and a decay time of approximately 100s was observed. Significant spectral changes occurred during the burst. The spectra were best fit by the black form with kT ranging from .87 keV to 2.3 keV. They suggest a source with smaller dimensions than a massive black hole. A weak source was observed after the burst with a 10 keV thermal spectrum and an indication of iron line emission.
    Keywords: SPACE RADIATION
    Type: NASA-TM-X-71195 , X-661-76-206
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  • 7
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    Two component X-ray emission from RS CVn binaries (1980)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A summary of results from the solid state spectrometer on the Einstein Observatory for 7 RS CVn binaries is presented. The spectra of all require two emission components, evidenced by line emission characteristic of plasma at 4 to 8 x 10 to the 6th power and bremsstrahlung characteristic of 20 to 100 x 10 to the 6th power K. The data are interpreted in terms of magnetic coronal loops similar to those seen on the Sun, although with different characteristic parameters. The emission regions could be defined by separate magnetic structures. For pressure less than approximately 10 dynes/sq cm the low temperature plasma would be confined within the stellar radii, while the high temperature plasma would, for the synchronous close binaries, fill the binary orbits. However, for loop pressures exceeding 100 dynes/sq cm, the high temperature components would also be confined to within the stellar radii, in loops covering only small fractions of the stellar surfaces. While the radio properties and the occurrence of X-ray flares suggest the larger emission regions, the observations of time variations leave the ambiguity unresolved.
    Keywords: SPACE RADIATION
    Type: NASA-TM-82045
    Format: application/pdf
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  • 8
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    Fine structure of a solar flare region at 3.7 and 11.1 cm wavelengths (1974)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Keywords: SPACE RADIATION
    Type: Solar Physics; 34; Jan. 197
    Format: text
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  • 9
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    The X-ray emitting galaxy Cen-A (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: OSO-8 X-ray observations of Cen-A in 1975 and 1976 are reported. The source spectrum is well fit in both years by a power law of number index 1.62 and absorption due to 1.3 x 10 to the 23rd power at/sq cm. The total flux varied by a factor 2 between 1975 and 1976. In 1976 there were approximately 40% flux variations on a time scale of days. The 6.4 keV Fe fluorescent line and the 7.1 keV absorption edge were measured implying Fe/H approximately equals .000016. Simultaneous radio measurements show variation in phase with X-ray variability. Models considering radio, milimeter, IR and X-ray data show that all the data can be accounted for by a model in which the X-rays are due to a synchrotron self-Compton source embedded in a cold H(2) cloud.
    Keywords: SPACE RADIATION
    Type: NASA-TM-X-71402 , X-661-77-237
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  • 10
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    Rapid X-ray variability from the Seyfert 1 Galaxy NGC 4051 (1983)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Strong variable X-ray emission from the nearby low luminosity Seyfert 1 galaxy NGC 4051 was discovered during observations with the imaging proportional counter of the Einstein Observatory. During one 2304 second observation, the X-ray flux more than doubled in an approximately linear fashion, and a 70% increase for 150 seconds was seen during another 968 second observation. Evidence is presented which demonstrates that the X-ray spectrum of NGC 4051 is unusually soft compared to Seyfert 1 galaxies or QSOs. The emission mechanism is probably not synchrotron or synchrotron self-Compton, but the emission can be plausibly explained by various black hole accretion models.
    Keywords: SPACE RADIATION
    Type: NASA-TM-84997 , NAS 1.15:84997
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