Spectral Properties of the X-Ray Objects GX 3 + 1, GX 354–5 and Sco XR-1

Buselli, G.; Clancy, Marie; Davison, P.; Edwards, P. R.; McCracken, K. G.; Thomas, Richard M.

doi:10.1038/2191124a0

Cited by 33 publications

(7 citation statements)

References 5 publications

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“…Our flux values at 60 and 63 keV obtained in two different flights agree with others. But the values are considerably higher than those of Buselli et al [6], who also find a flattening of the spectrum at high energies (KT~ 15 keV).…”

Section: Sco X-lcontrasting

confidence: 65%

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Energy spectra of several discrete X-ray sources in the 20–120 keV range

Agrawal

Biswas

Gokhale

et al. 1970

Symp. - Int. Astron. Union

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In this paper we report on our observations of hard X-rays from several X-ray sources in the energy range 20–120 keV. The results were obtained from the data collected during two balloon flights made from Hyderabad, India (latitude 17.6°N, longitude 78.5°E). The first flight was made on April 28, 1968, and the balloon reached a ceiling of about 5.3 g cm−2 residual atmosphere and floated from 0230 to 0800 hrs. IST (Indian Standard Time). The second balloon was launched on December 22, 1968 and floated at about 7.5 g cm−2 of residual air from 1000 to 1130 hrs. IST.

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Section: Sco X-lcontrasting

confidence: 65%

“…A comparison of the present data with the available spectral data [2][3][4][5][6][7][8] on Sco X-l is shown in Figure 2. It is clear from the figure that at any given energy the agreement in the absolute flux values is not better than by a factor of 2-3, at energies below 40 keV.…”

Section: Sco X-lmentioning

confidence: 95%

Energy spectra of several discrete X-ray sources in the 20–120 keV range

Agrawal

Biswas

Gokhale

et al. 1970

Symp. - Int. Astron. Union

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“…Scorpius X-1 is a high-luminosity LMXB Z source, where the primary is a neutron star with a low magnetic field. The presence of a nonthermal component in Sco X-1 has been suggested (e.g., Peterson & Jacobson 1966;Riegler, Bolt, & Serlemitsos 1970;Agrawal et al 1971;Haymes et al 1972;Duldig et al 1983), and the absence of such a component has also been reported (e.g., Lewin, Clark, & Smith 1967;Buselli et al 1968;Jain et al 1973;Johnson et al 1980). In fact, highsensitivity searches have failed to detect such a component, placing strong upper limits on the nonthermal flux (e.g., Greenhill et al 1979;Rothschild et al 1980;Soong & Rothschild 1983).…”

Section: Introductionmentioning

confidence: 98%

High-Energy X-Ray Timing Experiment Detections of Hard X-Ray Tails in Scorpius X-1

D'Amico

Heindl

Rothschild

et al. 2001

The Astrophysical Journal

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We report the detection of a nonthermal hard X-ray component from Sco X-1 based on the analysis of 20-220 keV spectra obtained with the High-Energy X-Ray Timing Experiment on board the Rossi X-Ray Timing Explorer satellite. We find that the addition of a power-law component to a thermal bremsstrahlung model is required to achieve a good fit in five of 16 observations analyzed. Using Proportional Counter Array data, we were able to track the movement of the source along the Z diagram, and we found that the presence of the hard X-ray tail is not confined to a specific Z position. However, we do observe an indication that the power-law index hardens with increasing , as indicated from the position on the Z diagram. We find that the deriveḋ M nonthermal luminosities are ∼10% of that derived for the brightest of the atoll sources.

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“…As for the unidentified galactic sources, many of the X-ray spectra are ill-known and still amenable to either a thermal or a power-law inter pretation. It has long been known, though, that the Sagittarius sources as a group are distinctly harder than Sco X-l (Giacconi et al, 1965), and lately we see that the individual spectra of Cyg X-l, Cyg X-3, Cyg X-4, Lup X-l, GX 3 4-1, and GX 354-5 all seem to prefer a power-law fit (Peterson et al, 1968;Buselli et al, 1968;Hudson et al, 1969;Rocchia et al, 1969). This tempts me, for one, to the hypothesis that most of the unidentified sources are supernova remnants, like the Crab, or related objects in the disk population.…”

Section: Other Galactic Sourcesmentioning

confidence: 60%

“…It was realized early that the X-ray spectrum of Sco X-l is nicely fitted by an ex ponential curve for optically thin thermal bremsstrahlung, with T&5x 10 7 K. More recently it has been confirmed that this best-fit T varies Chodil et al, 1968), and also that there is at high photon energies a nonthermal tail (Peterson and Jacobson, 1966;Buselli et al, 1968), apparently also variable (Lewin et al, 1968a;Overbeck and Tananbaum, 1968;Riegler, 1969). There is a correlation between the optical continuum brightness and the temperature of the thermal X-ray curve, but its nature is in doubt.…”

Section: Scorpius X-lmentioning

confidence: 94%

Theories of discrete X-ray and γ-ray sources: (Invited discourse)

Felten

1970

Symp. - Int. Astron. Union

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This is a critical review of theories of known discrete X-ray sources. The Crab is omitted, having been dealt with in Woltjer's review. Two of the identified sources, Sco X-1 and Cyg X-2, seem to be of the same sort. A binary or gas-stream model like that of Prendergast and Burbidge, with dimension R ∼ 109 cm and density n ∼ 1016 cm−3, appears reconcilable with the observed features of these sources, though much detailed work remains to be done. Neither object is yet known to be binary. Theoretical work becomes more difficult if, as appears to be the case at least for Sco X-1, the objects are optically thick due to electron scattering; this may affect the optical and X-ray spectra.The recent searches for iron lines in the X-ray spectrum of Sco X-1 are reviewed briefly. The calculations and the energy resolution are not yet good enough to make this a dependable test of models.Several possibilities are offered for explaining the excess radio flux from Sco X-1.Other theories of Sco X-1-type sources are discussed briefly. The theory of Manley and Olbert seems a little superfluous when the gas-stream theory is still in a strong position.There are serious discrepancies between X-ray and optical estimates of the distance to Sco X-1. 21-cm measurements must also be considered. The situation is reviewed, and ways out of the difficulty are discussed.Cen X-2 seems to be like Sco X-1, but several other unidentified sources have hard spectra like the Crab. It is tempting to speculate that most of the galactic sources are supernova remnants.The extended γ-ray source in the galactic plane may be the extrapolated unresolved sum of galactic X-ray sources, as suggested by Ogelman. There are several other possibilities.M87 is the only established extragalactic source. Radio, optical and X-ray observations are summarized and graphed. A power-law extrapolation to the X-ray band is far from mandatory; nevertheless the optical flux from the jet is known to be synchrotron radiation. The time-scale difficulties in the jet are described, and several theories of the survival of the optical electrons are reviewed.Processes for producing X-rays other than thermal bremsstrahlung and synchrotron radiation are listed. These other processes are characterized by low efficiency, and are likely to be unimportant in discrete sources, though several have attracted attention with reference to the diffuse background.

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Spectral Properties of the X-Ray Objects GX 3 + 1, GX 354–5 and Sco XR-1

Cited by 33 publications

References 5 publications

Energy spectra of several discrete X-ray sources in the 20–120 keV range

Energy spectra of several discrete X-ray sources in the 20–120 keV range

High-Energy X-Ray Timing Experiment Detections of Hard X-Ray Tails in Scorpius X-1

Theories of discrete X-ray and γ-ray sources: (Invited discourse)

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