Distribution and Variability of Cosmic X-Ray Sources

Friedman, H.; Byram, E. T.; Chubb, T. A.

doi:10.1126/science.156.3773.374

Cited by 121 publications

(50 citation statements)

References 10 publications

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“…GX 17+2 is one of strongest Galactic X-ray sources, and was detected in the sixties (e.g., Friedman et al 1967). Simultaneous X-ray and radio observations, performed by White et al (1978), did not show the presence of significant radio emission, but revealed correlated X-ray intensity and spectral variations similar to those already observed from Sco X-1.…”

Section: Gx 17+2mentioning

confidence: 70%

The transient hard X-ray tail of GX 17+2: New BeppoSAX results

Farinelli¹,

Frontera

Zdziarski

et al. 2005

A&A

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Abstract. We report on results of two BeppoSAX observations of the Z source GX 17+2. In both cases the source is in the horizontal branch of the colour-intensity diagram. The persistent continuum can be fit by two-component models consisting of a blackbody plus a Comptonization spectrum. With one of these models, two solutions for the blackbody temperature of both the observed and seed photons for Comptonization are equally accepted by the data. In the first observation, when the source is on the left part of the horizontal branch, we observe a hard tail extending up to 120 keV, while in the second observation, when the source moves towards right in the same branch, the tail is no longer detected. The hard ( > ∼ 30 keV) X-ray emission can be modeled either by a simple power-law with photon index Γ ∼ 2.8, or assuming Comptonization of ∼1 keV soft photons off a hybrid thermal plus non-thermal electron plasma. The spectral index of the non-thermal injected electrons is p ∼ 1.7. The observation of hard X-ray emission only in the left part of the horizontal branch could be indicative of the presence of a threshold in the accretion rate above which the hard tail disappears. An emission line at 6.7 keV with equivalent width ∼ 30 eV is also found in both observations. We discuss these results and their physical implications.

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Section: Gx 17+2mentioning

confidence: 70%

The transient hard X-ray tail of GX 17+2: New BeppoSAX results

Farinelli¹,

Frontera

Zdziarski

et al. 2005

A&A

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“…The neutron star LXMB Serpens X-1 was discovered in 1965 (Friedman et al 1967). Being a persistent, bright X-ray source, Serpens X-1 has been observed with major X-ray missions including Einstein (Vrtilek et al 1986), ASCA (Asai et al 2000), EXOSAT (Seon & Min 2002), BeppoSAX (Oosterbroek et al 2001), INTEGRAL (Masetti et al 2004), XMM-Newton (Bhattacharyya & Strohmayer 2007), Suzaku (Cackett et al 2008(Cackett et al , 2010, and recently with NuSTAR (Miller et al 2013).…”

Section: Introductionmentioning

confidence: 99%

A Test of the Nature of the Fe K Line in the Neutron Star Low-Mass X-Ray Binary Serpens X-1

Chiang

Cackett

Miller

et al. 2016

ApJ

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Broad Fe K emission lines have been widely observed in the X-ray spectra of black hole systems as well as in neutron star systems. The intrinsically narrow Fe K fluorescent line is generally believed to be part of the reflection spectrum originating in an illuminated accretion disk which is broadened by strong relativistic effects. However, the nature of the lines in neutron star low-mass X-ray binaries (LMXBs) has been a matter of debate. We therefore obtained the longest, high-resolution X-ray spectrum of a neutron star LMXB to date with a 300 ks Chandra High Energy Transmission Grating Spectrometer (HETGS) observation of Serpens X-1. The observation was taken under the "continuous clocking" mode, and thus was free of photon pile-up effects. We carry out a systematic analysis and find that the blurred reflection model fits the Fe line of Serpens X-1 significantly better than a broad Gaussian component does, implying that the relativistic reflection scenario is much preferred. Chandra HETGS also provides a highest spectral resolution view of the FeK region and we find no strong evidence for additional narrow lines.

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“…Figure 17 shows the source Norma XR-2 at 15 hr, 32minr.a., -57° dec. This source was first identified in a rocket survey (Friedman et al, 1967), observed from a balloon by Lewin and Clark (Lewin et al, 1968b) and was previously identified erroneously with Lupus XR-1 in a UCSD preprint . No significant change was observed in this The variable X-ray source Centaurus XR-2 has also been observed by the OSO-III.…”

Section: Id 4 -mentioning

confidence: 97%

Properties of individual X-ray sources: (Invited discourse)

Peterson

1970

Symp. - Int. Astron. Union

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Abstract. Observations to determine the spectra and time variations of hard X-rays from cosmic sources have been made from balloons and from the OSO-III satellite. These data have been obtained using actively collimated scintillation counters with apertures between 6 and 24° FWHM, areas between 10 and 50 cm 2 and which operate over the 10-300 keV range. The Crab Nebula has been observed on three occasions over a 22-month period between September 1965 and July 1967. The power law spectrum has a number index of 2.0 ± 0.1. No long-term changes were observed over the 30-100keV range with a limit at 3%/yr. A balloon search with a 10 cm 2 Ge(Li) detector for X-ray lines at 62.5 keV, 110 keV and 180 keV due to heavy element radioactive decays which would be produced in the initial Crab explosion based on the Cf 254 hypothesis has resulted in upper limits at about 10" 3 y-rays cm 2 -sec. This is about a factor of 20 above the predicted levels. Simultaneous X-ray and optical observations of SCO XR-1 from OSO-III confirm that X-ray and optical flaring are indeed coincident phenomena, and that although the X-ray intensity increases about a factor of two during the flare, the equivalent temperature of the excess radiation is nearly the same as that of the quiescent object. Upper limits, 95% confidence, on the flux of M-87 at 40 keV have been obtained. These are inconsistent with the flux of 1.2 x 10~4 photons/cm 2 -sec-keV reported in the literature. CYG X-l has been observed to have a power law of number index 2.0 ± 0.2. The OSO-III has observed a number of sources in the southern skies including NOR XR-2 and the variable source Centaurus XR-2.

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Distribution and Variability of Cosmic X-Ray Sources

Cited by 121 publications

References 10 publications

The transient hard X-ray tail of GX 17+2: New BeppoSAX results

The transient hard X-ray tail of GX 17+2: New BeppoSAX results

A Test of the Nature of the Fe K Line in the Neutron Star Low-Mass X-Ray Binary Serpens X-1

Properties of individual X-ray sources: (Invited discourse)

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