A High‐Sensitivity Measurement of the MeV Gamma‐Ray Spectrum of Cygnus X‐1

McConnell, Mark L.; Ryan, J. M.; Collmar, W.; Schönfelder, V.; Steinle, H.; Strong, A. W.; Bloemen, H.; Hermsen, W.; Kuiper, L.; Bennett, K.; Phlips, Bernard F.; Ling, J. C.

doi:10.1086/317128

Cited by 106 publications

(146 citation statements)

References 57 publications

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“…Observations with the INTEGRAL satellite have confirmed the existence of a supra-thermal tail in the spectrum (Cadolle Bel et al 2006). So-called hybrid thermal/non-thermal models from Poutanen & Svensson (1996) and Coppi (1999) have been used to fit the observed spectrum (McConnell et al 2000;Cadolle Bel et al 2006). These models consider a hybrid pair plasma with a non-thermal component.…”

Section: Application To Cygnus X-1mentioning

confidence: 99%

“…These models consider a hybrid pair plasma with a non-thermal component. In particular, using the EQPAIR code, McConnell et al (2000) concluded that either the magnetic field in Cyg X-1 is substantially below equipartition (at least to within an order of magnitude) or the observed photon tail has a different origin than that related to locally accelerated electrons.…”

Section: Application To Cygnus X-1mentioning

confidence: 99%

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Non-thermal processes around accreting galactic black holes

Romero

Vieyro²,

Vila³

2010

A&A

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Context. Accreting black holes in galactic X-ray sources are surrounded by hot plasma. The innermost part of these systems is likely a corona with different temperatures for ions and electrons. In the so-called low-hard state, hot electrons Comptonize soft X-ray photons from the disk that partially penetrates the corona, producing emission up to ∼150 keV, well beyond the expectations for an optically thick disk of maximum temperature ∼10 7 K. However, sources such as Cygnus X-1 produce steady emission up to a few MeV, which is indicative of a non-thermal contribution to the spectral energy distribution. Aims. We study the radiative output produced by the injection of non-thermal (both electron and proton) particles in a magnetized corona around a black hole. Methods. Energy losses and maximum energies are estimated for all types of particles in a variety of models, characterized by different kinds of advection and relativistic proton content. Transport equations are solved for primary and secondary particles, and spectral energy distributions are determined and corrected by internal absorption. Results. We show that a local injection of non-thermal particles can account for the high energy excess observed in some sources, and we predict the existence of a high-energy bump at energies above 1 TeV, and typical luminosities of ∼10 33 erg s −1 . Conclusions. High-energy instruments such as the future Cherenkov Telescope Array (CTA) can be used to probe the relativistic particle content of the coronae around galactic black holes.

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Section: Application To Cygnus X-1mentioning

confidence: 99%

Section: Application To Cygnus X-1mentioning

confidence: 99%

Non-thermal processes around accreting galactic black holes

Romero

Vieyro²,

Vila³

2010

A&A

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“…Cyg X-1 was observed by the instruments aboard the Compton Gamma Ray Observatory on several occasions during the first three cycles (1991)(1992)(1993)(1994), when the source was in a low/hard state (McConnell et al 2000). COMPTEL measured an energy spectrum described by a simple power-law with photon index 3.3 ± 0.4, between 0.75 and 5 MeV.…”

Section: The Search For Gamma Ray Emissionmentioning

confidence: 99%

“…During the first three cycles of observation (1991)(1992)(1993)(1994) of the Compton Gamma Ray Observatory (CGRO), the source, in hard state, was detected by COMPTEL only between 2 and 5 MeV (see McConnell et al 2000, for details). EGRET did not detect the source during that observation and the upper limit to the flux is of the order of 10 × 10 −8 ph cm −2 s −1 , posing no need for a high-energy cut-off.…”

Section: Introductionmentioning

confidence: 99%

A year-long AGILE observation of Cygnus X-1 in hard spectral state

Monte¹,

Feroci²,

Evangelista

et al. 2010

A&A

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Context. Cygnus X-1 (Cyg X-1) is a high mass X-ray binary system, known to be a black hole candidate and one of the brightest sources in the X-ray sky, which shows both variability on all timescales and frequent flares. The source spends most of the time in a hard spectral state, dominated by a power-law emission, with occasional transitions to the soft and intermediate states, where a strong blackbody component emerges. Aims. We present the observation of Cyg X-1 in a hard spectral state performed during the AGILE science verification phase and observing cycle 1 in hard X-rays (with SuperAGILE) and gamma rays (with the gamma ray imaging detector) and lasting for about 160 days with a live time of ∼6 Ms. Methods. We investigated the variability of Cyg X-1 in hard X-rays on different timescales, from ∼300 s up to one day, and we applied different tools of timing analysis, such as the autocorrelation function, the first-order structure function, and the LombScargle periodogram, to our data (from SuperAGILE) and to the simultaneous data in soft X-rays (from RXTE/ASM). We concluded our investigation with a search for emission in the energy range above 100 MeV with the maximum likelihood technique. Results. In the hard X-ray band, the flux of Cyg X-1 shows its typical erratic fluctuations on all timescales with variations of about a factor of two that do not significantly affect the shape of the energy spectrum. From the first-order structure function, we find that the X-ray emission of Cyg X-1 is characterized by antipersistence (anticorrelation in the time series, with an increase in the emission likely followed by a decrease), indicative of a negative feedback mechanism at work. In the gamma ray data a statistically significant point-like source at the position of Cyg X-1 is not found, and the upper limit on the flux is 5 × 10 −8 ph cm −2 s −1 over the whole observation (160 days). Finally we compared our upper limit in gamma rays with the expectation of various models of the Cyg X-1 emission, both of hadronic and leptonic origin, in the GeV-TeV band. Conclusions. The time history of Cyg X-1 in the hard X-ray band over 13 months (not continuous) is shown. Different analysis tools do not provide fully converging results of the characteristic timescales in the system, suggesting that the timescales found in the structure function are not intrinsic to the physics of the source. While Cyg X-1 is not detected in gamma rays, our upper limit is a factor of two lower than the EGRET one and is compatible with the extrapolation of the flux measured by COMPTEL in the same spectral state.

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“…We also took into account the effect of secondary pairs created by photon-photon pair production. Figure (1) shows the total SED together with the spectrum of Cygnus X-1, detected by COMPTEL McConnell et al (2000) and the radio detection of the jet by Stirling et al (2001).…”

Section: Static Corona Modelmentioning

confidence: 99%