The states of Cygnus X-1

Ling, J. C.; Mahoney, W. A.; Wheaton, W. A.; Jacobson, Allan; Kaluzienski, L. J.

doi:10.1086/161534

Cited by 36 publications

(27 citation statements)

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“…The source was first discovered by BATSE (Harmon et al 1993) and SIGMA (Ballet et al 1993). Ling & Wheaton (2004) showed that the hard X-ray flux rose suddenly from the quiescent level before 17 September 1993 (TJD 9247) to ∼1.5 Crab 16 days later on 3 October (TJD 9263). It then slowly decreased in the next 70 days to ∼1 Crab level on 12 December (TJD 9333) (la- Fig.…”

Section: Resultsmentioning

confidence: 99%

“…This high-level database (levels 2 & 3) consists of daily gamma-ray spectra with 14 energy channels between 35 keV and 1.7 MeV, and six broad-band flux histories with 1-day resolution for each of the 75 gamma-ray sources, currently included in the EBOP source catalog. In this paper, we focus on the soft γ-ray emission of three black holes in our galaxy: GRO J1719 − 24 (Ling & Wheaton 2004), GRO J0422+32 (Ling & Wheaton 2003), and Cygnus X-1 (Ling et al 1997;Zhang et al 1997) observed by BATSE. All three sources underwent multiple gamma-ray flux transitions during this 9-year period between low and high-intensity gamma-ray states.…”

Section: Introductionmentioning

confidence: 99%

“…Implications of these results in enhancing our understanding of these systems are discussed in Section 3. Figure 1 shows the soft γ-ray flux histories of GRO J1719−24 (Ling & Wheaton 2004), GRO J0422+32 (Ling & Wheaton 2003) and Cygnus X-1 covering the periods from 13 January 1993 to 10 October 1995 (TJD 9000-10000), 27 June 1992 to 23 April 1993 (TJD 8800-9100), and 24 May 1991 to 26 May 2000 (TJD 8400-11690, the full 9-year CGRO mission), respectively. During these periods, all three sources underwent multiple flux transitions.…”

Section: Introductionmentioning

confidence: 99%

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Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

Ling

Wheaton

2005

Chin. J. Astron. Astrophys.

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Cygnus X-1 and the gamma-ray transients GRO J0422+32 and GRO J1719 − 24 displayed similar spectral properties when they underwent transitions between the high and low gamma-ray (30 keV to few MeV) intensity states. When these sources were in the high γ-ray intensity state (γ 2 , for Cygnus X-1), their spectra featured two components: a Comptonized shape below 200-300 keV with a soft power-law tail (photon index >3) that extended to ∼1 MeV or beyond. When the sources were in the low-intensity state (γ 0 , for Cygnus X-1), the Comptonized spectral shape below 200 keVtypically vanished and the entire spectrum from 30 keV to ∼1 MeV can be characterized by a single power law with a relatively harder photon index ∼ 2 − 2.7. Consequently the high-and low-intensity gammaray spectra intersect, generally in the ∼400 keV -∼1 MeV range, in contrast to the spectral pivoting seen previously at lower (∼10 keV) energies. The presence of the power-law component in both the high-and low-intensity gamma-ray spectra strongly suggests that the non-thermal process is likely to be at work in both the high and the low-intensity situations. We have suggested a possible scenario (Ling & Wheaton, 2003), by combining the ADAF model of Esin et al. (1998) with a separate jet region that produces the non-thermal gamma-ray emission, and which explains the state transitions. Such a scenario will be discussed in the context of the observational evidence, summarized above, from the database produced by EBOP, JPL's BATSE earth occultation analysis system.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

Ling

Wheaton

2005

Chin. J. Astron. Astrophys.

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“…It spends a large fraction of its time in a spectrally hard, highly variable X-ray state; however, it occasionally transits to a softer, less variable state [265][266][267]. Several such transitions to a soft state have been observed with RXTE [61,62,268].…”

Section: A Case Study Of Cygnus X-1mentioning

confidence: 99%

Fluorescent iron lines as a probe of astrophysical black hole systems

2003

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“…It has long been recognized that the soft X-ray emission of Cygnus X-1 (~10 keV) generally varies between two discrete levels [1,2]. The 20-100 keV time history of Cygnus X-1, as derived from BATSE occultation data, is shown in the center panel of Figure 1.…”

Section: Introductionmentioning

confidence: 99%

Gamma-ray spectral variability of Cygnus X-1

McConnell¹,

Bennett²,

Bloemen³

et al. 2001

AIP Conference Proceedings

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Abstract. We have used observations from CGRO to study the variation in the MeV emission of Cygnus X-1 between its low and high X-ray states. These data provide a measurement of the spectral variability above 1 MeV. The high state MeV spectrum is found to be much harder than that of the low state MeV spectrum. In particular, the power-law emission seen at hard X-ray energies in the high state spectrum (with a photon spectral index of 2.6) is found to extend out to at least 5 MeV, with no evidence for any cutoff. Here we present the data and describe our efforts to model both the low state and high state spectra using a hybrid thermal/nonthermal model in which the emission results from the Comptonization of an electron population that consists of both a thermal and nonthermal component.

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The states of Cygnus X-1

Cited by 36 publications

References 0 publications

Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

Gamma-Ray Spectral Characteristics of Thermal and Non-Thermal Emission from Three Black Holes

Fluorescent iron lines as a probe of astrophysical black hole systems

Gamma-ray spectral variability of Cygnus X-1

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