Observations of Cygnus X-1 COMPTEL during 1991

McConnell, M.; Forrest, D. J.; Ryan, J.; Collmar, W.; Schöenfelder, V.; Steinle, H.; Strong, A. W.; Dijk, R. van; Hermsen, W.; Bennett, K.

doi:10.1086/173941

Cited by 46 publications

(52 citation statements)

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“…These results are in accordance with the higher temperatures (~ 200 keV) found by COMPTEL for Cyg X-1 [6]. The quality of the fits with the use of the Wien type spectrum were generally not very good and show significant deviations from the Comptonisation models at the higher energy intervals (300... 700 keV) of SIGMA (5.8 a deviation) [9] and at the COMPTEL energies (2.8 a) [5].…”

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confidence: 83%

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Comptel Observations of X-Ray Binaries

Iyudin¹

1996

International Astronomical Union Colloquium

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The COMPTEL experiment on the Compton Gamma-Ray Observatory measures 7-radiation in the energy range from 0.75 to 30 MeV [10]. X-ray binaries form one category of potential 7-ray sources. Up to now only two X-ray binaries, Cyg X-l and Nova Per, have been seen by COMPTEL.Cyg X-l. Preliminary results were reported by [6] and indicate that (i) there was no evidence for any hardening of the spectrum near 1 MeV, (ii) the plasma temperature suggested by a Wien spectral model was much higher than that implied by hard X-ray observations. This latter conclusion seems to require a revision in the standard spectral model for Cyg X-l.The 7-ray flux from Cyg X-l is constant up to several MeV. The time history of the flux in the 0.75... 2.0 MeV energy range shows that there are no significant variations near 1 MeV.

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confidence: 83%

“…Preliminary results were reported by [6] and indicate that (i) there was no evidence for any hardening of the spectrum near 1 MeV, (ii) the plasma temperature suggested by a Wien spectral model was much higher than that implied by hard X-ray observations. This latter conclusion seems to require a revision in the standard spectral model for Cyg X-l.…”

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confidence: 88%

Comptel Observations of X-Ray Binaries

Iyudin¹

1996

International Astronomical Union Colloquium

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“…The black hole spectra in the hard state instead show a cutoff at ∼ 100 keV [3][4][5] and can be fit quite well with thermal Comptonization models up to energies ∼ 300 keV. However, there is evidence in the COMPTEL and BATSE data that the hard state spectrum of Cyg X-1 show high energy excess at > ∼ 500 keV [6,7]. This excess can be interpreted as a signature of non-thermal electrons in the X/γ-ray source [8,9].…”

Section: Observations Of Galactic Black Holesmentioning

confidence: 99%

“…The simultaneous hard-state observations by Ginga, OSSE and COMPTEL [4,6] are analyzed together. For the soft state, publically available XTE/PCA and OSSE data from June 1996 are analyzed.…”

Section: Spectral Statesmentioning

confidence: 99%

Unification of Spectral States of Accreting Black Holes

1998

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Several galactic black holes show transitions between spectral states. The nature of these transitions is not fully understood yet. None of the dynamical accretion disk models can fully describe spectral transitions. In this paper we present a unifying radiation transfer model that can fit the spectral data in both states. Since Cyg X-1 has the best available data, we focus here on modeling this object. We fit individual broad-band (from 1 keV up to 4 MeV) spectral data for the "hard" and "soft" states of Cyg X-1 using an emission model where a central Comptonizing corona/cloud is illuminated by the soft photon emission from a cold disk. We assume that the energy is injected to the corona by two channels: a non-thermal one that injects energetic (> MeV) electrons into the coronal region, and a thermal one that heats injected and ambient electrons once they cool sufficiently to form a Maxwellian distribution, i.e., we consider a hybrid thermal/non-thermal model. The process of photon-photon pair production is included in the model, and the number of pairs produced in the coronal region can be substantial.Using simple scaling laws for the luminosity of the cold disk, the thermal dissipation/heating rate in the corona, and the rate of energy injection from a non-thermal source, all as functions of radius of the corona, we explain the hard-to-soft transition as the result of a decrease in the size of the corona and the inner radius of the cold disk by a factor ∼ 5. For the case of Cyg X-1, we show that the bolometric luminosity of the source (mass accretion rate) does not change significantly during the transition, and thus the transition is probably the result of a disk instability. Observations of Galactic Black HolesGalactic black holes radiate X-rays and γ-rays in one of several spectral states. Recently, it has become clear that in the soft state, the power-law spectrum (with typical energy spectral index α ∼ 1.5) extends to photon energies ∼ m e c 2 without any obvious break [1][2][3]. The black hole spectra in the hard state instead show a cutoff at ∼ 100 keV [3][4][5] and can be fit quite well with thermal Comptonization models up to energies ∼ 300 keV. However, there is evidence in the COMPTEL and BATSE data that the hard state spectrum of Cyg X-1 show high energy excess at > ∼ 500 keV [6,7]. This excess can be interpreted as a signature of non-thermal electrons in the X/γ-ray source [8,9]. This excess can also be explained in terms of a multi-zone models where thermal electrons have significantly different temperatures [7,10,11].While the data in any one state can be fit quite successfully by one of the models mentioned above, none of the models proposed thus far can fit data from both states. Esin et al. [12] explain the spectral transitions in terms of the advection dominated disks. Their prediction that electron temperature in the soft state should be smaller than that in the hard state (because of the significant increase in the number of ambient soft photons) is in perfect agreement with our f...

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“…Other groups have also reported measurements of MeV emission from Cyg X-1 see Owens and McConnell 1992 for a review of the MeV observations. Recently, Harris et al 1993 derived upper limits for aring episodes of 12 or more days from the long-term data base of the gamma ray spectrometer on SMM, and McConnell et al 1994 reported no evidence for MeV features from the Cyg X-1 in data from COMPTEL.…”

Section: Introductionmentioning

confidence: 99%

Gamma Ray Observations of Cygnus X-1 With OSSE

Phlips

Jung

Leising

et al. 1996

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Abstract. We report on 120 days of observations of Cygnus X-1 with OSSE onboard the Compton Observatory. Emission is detected in the range 50 keV to 1 MeV, and we nd evidence for a continuum of hard X-ray spectra over a broad range of uxes rather than the existence of distinct ux states. Comparisons of the source spectra with various theoretical models show that an exponentially truncated power law best describes the average spectrum in the OSSE energy band. Although we h a v e measured a new minimum in the hard X-ray ux from the source, no evidence was found for either a broad 1 MeV feature or a narrow 511 keV line previously reported in association with a low ux state. Upper limits on such emission features are an order of magnitude lower than earlier reported detections. The 5.6-day periodicity of the source measured at optical wavelengths was not detected with a sensitivity to the rms modulation fraction of 5 in the 60-140 keV energy band.

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Observations of Cygnus X-1 COMPTEL during 1991

Cited by 46 publications

References 0 publications

Comptel Observations of X-Ray Binaries

Comptel Observations of X-Ray Binaries

Unification of Spectral States of Accreting Black Holes

Gamma Ray Observations of Cygnus X-1 With OSSE

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