X-Ray Spectra from Three Cosmic Sources

Grader, R. J.; Hill, Randal M.; Seward, F. D.; Toor, A.

doi:10.1126/science.152.3728.1499

Cited by 60 publications

(23 citation statements)

References 8 publications

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“…These spectra were a factor of two less than some early proportional counter measurements (Chodil et al 1965;Grader et al 1966;Hayakawa, Matsuoka, and Yamashita 1966) but were consistent with the less accurate flux measurements made by other early experimenters (Bowyer et al 1964;Giacconi, Gursky, and Waters 1965). Manley (1967) has suggested that the discrepancy was instrumental in origin and did not represent a real variation.…”

Section: Pectrasupporting

confidence: 85%

Observations of Cen XR?2, SCO XR?1, and Terrestrial X-Rays

Harries¹,

Francey²

1968

Aust. J. Phys.

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SummaryTwo identical X-ray experiments were flown on Skylark rockets from Woomera, Australia, during April 1967. Sco XR-l and Cen XR-2 were observed on both flights. The Cen XR-2 flux was (1-5±0'1) X 10-7 erg cm-2 sec-1 (2-8 keY) when first observed but had decreased to (l·0±0·1) X 10-7 erg cm-2 sec-1 and had become softer by the second flight. An X-ray flux from the Earth was observed and found to be due to solar X-rays reflected in the atmosphere.

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Section: Pectrasupporting

confidence: 85%

Observations of Cen XR?2, SCO XR?1, and Terrestrial X-Rays

Harries¹,

Francey²

1968

Aust. J. Phys.

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“…The data points presented were specifically analyzed for evidence of interstellar absorption at lower energies, but no statistically significant absorption was needed to produce a fit to a spectrum characteristic of either bremsstrahlung or synchrotron radiation. The power law spectrum characteristic of synchrotron radiation that Gorenstein et al derive is given by Equation (5); the continuous nature of the spectrum as observed by Grader et al (1966) andChodil et al (1967) between 10 and 20 keV (see Figures 4 and 29) favors the choice of the power law spectrum as a better representation of the observations. Meekins et al (1969) observed Cyg XR-1 with three thin window proportional counters aboard a rocket launched from White Sands, New Mexico at 0321 UT, September 8, 1967 (JD 2439741.64).…”

Section: B the Flux At Energies Between 1 And 20 Kevmentioning

confidence: 97%

“…Figure The flux observed from Cyg XR-1 was assigned by the authors to the energy interval between 1.5 and 15 keV; this is the position we have assigned it in Figure 31. Figure 4, discussed above, also contains observations of the flux of Cyg XR-1 at energies below 20 keV taken by Grader et al (1966). It was included in the earlier section of this paper because it also contained observations of the object at energies above 20 keV.…”

Section: B the Flux At Energies Between 1 And 20 Kevmentioning

confidence: 99%

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The variable X-ray spectrum of Cyg XR-1

Dolan

1970

Space Sci Rev

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The variability of the X-ray spectrum of the discrete source Cyg XR-1 (c~ = 19 h 56m) = q-35~ is reviewed. The variations observed in the energy region accessible to balloon borne detectors (energies greater than 20 keV) can be explained by assuming them to be caused by the eclipsing properties of a binary system. It is suggested that the system is composed of a source of small angular extent having a spectrum similar to that of a black body at approximately 1.5 x 108 K (kT= 12.5 keV) and a non X-radiating companion which eclipses it at intervals of 2.9850 days. The system would be surrounded by an X-radiating plasma whose photon flux between 1 and 100 keV can be approximated by a power law spectrum whose exponent is --1.7.The discrete X-ray source located at e= 19h56 m, 6= +35.~ and ordinarily designated as Cyg XR-1 (Friedman et al., 1967) is one of the brightest celestial objects in the X-ray region above 20 keV. Because of this, observations have been made of the object since 1964 by balloon borne detectors as well as by rocket borne instrumentation. Although the first observations of the object in the X-ray region below 10 keV led Byram et al. (1966) to make the suggestion that the source was of variable intensity, a more frequent series of measurements taken by balloon borne equipment gave the first convincing proof of the intrinsic variability of the object (see Overbeck and Tananbaum, 1968a), at least in the region above 20 keV. It is profitable to review the variability of the object in the energy regions specified above from the standpoint of deciding whether any regularity, either in spectral shape vs. intensity or in intensity vs. time, can be deduced from the observations.

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“…https://doi.org/10.1017/S0074180900100269 a quite significant fraction are associated with the region of the galactic nucleus . Unless these are objects of an entirely unexpected sort, many are pre sumably mass transfer binaries in the stellar population associated with the galactic nuclear region, viz., an old metal-rich population similar to the stars in galactic clusters like M 67 and N G C 7 5 2 (Arp, 1965;Van den Bergh, 1972) or globular clusters like M 71 (Arp and Hartwick, 1971) and N G C 6352 (Hartwick and Hesser, 1972). This means we are dealing with binary systems in which the primaries are of relatively low mass, i.e., in the range 1 to 2 m© (cf.…”

Section: Some Boundary Conditions On Possible Mass-transfer Modelsmentioning

confidence: 99%

Binary Systems as X-Ray Sources: A Review

Kraft

1973

Symp. - Int. Astron. Union

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Abstract. The observational properties of Sco X-l, Cyg X-2, and Cen X-3 are reviewed in connection with the hypothesis that X-ray power is derived from gravitational energy released when matter is accreted onto the surface of one component in a mass transfer binary star. Evolutionary mechanisms for producing suitable types of binaries are considered. The following boundary conditions on pos sible evolutionary models are also treated briefly: (1) a quite significant fraction of hard X-ray sources are associated with the nuclear bulge of the galaxy; (2) mass-transfer binaries such as U Gem stars are not hard X-ray sources; (3) counts of binary stars lead to a considerably larger number of X-ray source candidates than are actually observed.

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X-Ray Spectra from Three Cosmic Sources

Cited by 60 publications

References 8 publications

Observations of Cen XR?2, SCO XR?1, and Terrestrial X-Rays

Observations of Cen XR?2, SCO XR?1, and Terrestrial X-Rays

The variable X-ray spectrum of Cyg XR-1

Binary Systems as X-Ray Sources: A Review

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