OSSE Observations of Blazars

McNaron-Brown, K.; Grove, J. E.; Johnson, W. N.; Kinzer, R. L.; Kroeger, R. A.; Kurfess, J. D.; Grabelsky, D. A.; Purcell, W. R.; Jung, G. V.; Cameron, R. A.

doi:10.1086/176245

Cited by 83 publications

(77 citation statements)

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“…All MeV light curves are statistically consistent with a constant flux for both sources during the analyzed period of 7 years, although flux variations were found in neighboring bands by OSSE (McNaron-Brown et al 1995) and EGRET (Mukherjee et al 1997) for both sources. The COMPTEL 10−30 MeV detections are weak for both sources.…”

Section: Flux Variabilitysupporting

confidence: 70%

“…In pure SSC models, the high-energy peak relates to the low-energy one by ν C ∝ γ 2 ν S , where ν S is the frequency of the synchrotron peak, ν C the frequency of the SSC peak, and γ the average Lorentz-factor (energy) of the electrons. In a SSC scenario, γ should be in the range of 10 3 −10 5 for 3C 454.3 and CTA 102 according to the peak The solid lines with triangles on each end represent the time-averaged (Phase 1−4) EGRET spectra , open circles the COMPTEL measurements (all mission), " * " the OSSE observations in 1994 (McNaron-Brown et al 1995), and filled squares the ASCA measurements in 1995 (taken from NED). The low-energy data symbolized by open diamonds are taken from Montigny et al (1995), and the ones symbolized by open squares from Impey et al (1988). positions in their SEDs (Fig.…”

Section: Discussionmentioning

confidence: 99%

“…flux variability and a power-law shaped spectrum of energy index ∼0.6 for 3C 454.3 (Comastri et al 1997). At hard X-rays, 3C 454.3 and CTA 102 were occasionally detected by OSSE at energies between 50 keV and 1 MeV, both showing flux variability (McNaron-Brown et al 1995). Blom et al (1995) reported the COMPTEL MeV-detections of both sources during the early CGRO observations in 1991 and 1992.…”

Section: Introductionmentioning

confidence: 91%

“…To verify this trend, we added non-simultaneous published (McNaron-Brown et al 1995) OSSE data, measured for both sources in 1994 (VPs 317, 319, 319.5 and 323 for 3C 454.3; VPs 316, 317 and 323 for CTA 102). These combined OSSE/COMPTEL/EGRET spectra show clearly the spectral turnover with a power maximum in the COMPTEL range for both sources (Fig.…”

Section: Energy Spectramentioning

confidence: 99%

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COMPTEL observations of the γ-ray blazars 3C 454.3 and CTA 102 during the CGRO mission

Zhang

Collmar

Schönfelder

2005

A&A

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We have investigated the MeV behaviour of the γ-ray blazars 3C 454.3 and CTA 102 by analyzing all COMPTEL observations of this sky region during the complete CGRO mission. Both sources are detected by COMPTEL at the upper COMPTEL energies, although their flux estimates may be uncertain by possible minor contributions of nearby unidentified EGRET γ-ray sources. While CTA 102 was only detected at energies above 10 MeV during the early mission, 3C 454.3 is most significantly detected in the COMPTEL 3−10 MeV band in the sum of all data. Time-resolved analyses indicate a weak (near COMPTEL threshold) but likely steady 3−10 MeV emission over years, being independent of the observed time variability at energies above 100 MeV as observed by EGRET. This energy-dependent variability behaviour suggests different emission mechanisms at work in the two bands. Putting the COMPTEL fluxes in multifrequency perspective (radio to γ-rays) reveals for both sources the typical two-hump blazar spectrum, with a low-energy maximum around the IR and a high-energy maximum at MeV energies. The latter one dominates the energy output across the whole electro-magnetic spectrum. The results of our analyses are discussed in the framework of current blazar modeling.

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Section: Flux Variabilitysupporting

confidence: 70%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 91%

Section: Energy Spectramentioning

confidence: 99%

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COMPTEL observations of the γ-ray blazars 3C 454.3 and CTA 102 during the CGRO mission

Zhang

Collmar

Schönfelder

2005

A&A

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“…Therefore, we require that the model spectrum must agree with the data Table 1. Historical data, as compiled by Ostorero et al (2006) and shown as grey symbols, at radio-to-optical frequencies are from Kuehr et al (1981), Waltman et al (1981), Eckart et al (1982), Perley (1982), Perley et al (1982), Lawrence et al (1985), Saikia et al (1987), Kuehr & Schmidt (1990), Moshir et al (1990), Hales et al (1991), Krichbaum et al (1993), Gear et al (1994), Hales et al (1995), Douglas et al (1996), Rengelink et al (1997), Zhang et al (1997), Riley et al (1999), Cohen et al (2002), Raiteri et al (2003); UV data from Pian & Treves (1993), Ghisellini et al (1997); X-ray data from Biermann et al (1992), Comastri et al (1997), Kubo et al (1998), Giommi et al (1999), Tagliaferri et al (2003), Pian et al (2005); and γ-ray data from McNaron-Brown et al (1995), Hartman et al (1999), Collmar (2006). at these two frequencies.…”

Section: Injection Of Electrons In a Double Power Lawmentioning

confidence: 99%

A synchrotron self-Compton model with low-energy electron cut-off for the blazar S5 0716+714

Tsang

Kirk

2007

A&A

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Context. In a self-absorbed synchrotron source with power-law electrons, rapid inverse Compton cooling sets in when the brightness temperature of the source reaches T B ∼ 10 12 K. However, brightness temperatures inferred from observations of intra-day variable sources (IDV) are well above the "Compton catastrophe" limit. This can be understood if the underlying electron distribution cuts off at low energy. Aims. We examine the compatibility of the synchrotron and inverse Compton emission of an electron distribution with low-energy cut-off with that of IDV sources, using the observed spectral energy distribution of S5 0716+714 as an example. Methods. We compute the synchrotron self-Compton (SSC) spectrum of monoenergetic electrons and compare it to the observed spectral energy distribution (SED) of S5 0716+714. The hard radio spectrum is well-fitted by this model, and the optical data can be accommodated by a power-law extension to the electron spectrum. We therefore examine the scenario of an injection of electrons, which is a double power law in energy, with a hard low-energy component that does not contribute to the synchrotron opacity. Results. We show that the double power-law injection model is in good agreement with the observed SED of S5 0716+714. For intrinsic variability, we find that a Doppler factor of D ≥ 30 can explain the observed SED provided that low-frequency (<32 GHz) emission originates from a larger region than the higher-frequency emission. To fit the entire spectrum, D ≥ 65 is needed. We find the constraint imposed by induced Compton scattering at high T B is insignificant in our model. Conclusions. We confirm that electron distribution with a low-energy cut-off can explain the high brightness temperature in compact radio sources. We show that synchrotron spectrum from such distributions naturally accounts for the observed hard radio continuum with a softer optical component, without the need for an inhomogeneous source. The required low energy electron distribution is compatible with a relativistic Maxwellian.

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Studies of bright flat‐spectrum radio quasar 3C 454.3 at high and very‐high‐energies

Sinitsyna,

Borisov

2024

Astron Nachr

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Blazars are the subclass of active galactic nuclei (AGNs) which includes the Flat Spectrum Radio Quasars (FSRQ) and BL Lacertae (BL Lac) objects. Variability on the short‐ and long‐time scale in all the wide energy ranges from radio up to gamma‐ray emission is a special characteristic of blazars. Multi‐wavelength studies of the flaring activity and variability of blazars can serve as a tool to probe the physical properties of the near the core regions and processes responsible for the observed features. 3C 454.3 is a bright FSRQ that is intensively studied through the wide range of electromagnetic spectrum. It has shown remarkably high activity since 2000. The long‐term observations of 3C 454.3 at 800 GeV–100 TeV energies with the SHALON telescope were started in 1998 year. A number of activity periods were found. The most significant flaring state of 3C 454.3 at TeV energies was detected in the SHALON observational period of November–December 2010. This increase is correlated with the flares at a lower energy range in observations of Fermi‐LAT. The direct association of the significant changes of gamma‐ray flux with strong core radio flares are not clear but observed correlations and lags in multi‐wavelength activity may point to the complexity of the emission processes in blazars connected with disturbance propagating in the jet.

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OSSE Observations of Blazars

Cited by 83 publications

References 0 publications

COMPTEL observations of the γ-ray blazars 3C 454.3 and CTA 102 during the CGRO mission

COMPTEL observations of the γ-ray blazars 3C 454.3 and CTA 102 during the CGRO mission

A synchrotron self-Compton model with low-energy electron cut-off for the blazar S5 0716+714

Studies of bright flat‐spectrum radio quasar 3C 454.3 at high and very‐high‐energies

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