In‐Flight Calibration of EGRET on the
                    <i>Compton Gamma‐Ray Observatory</i>

Esposito, J. A.; Bertsch, D. L.; Chen, Andrew; Dingus, B. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mayer‐Hasselwander, H. A.; McDonald, L. M.; Michelson, P. F.; Montigny, C. von; Mukherjee, R.; Nolan, P. L.; Reimer, O.; Schneid, E. J.; Sreekumar, P.; Thompson, D. J.; Tompkins, W. F.; Willis, T. D.

doi:10.1086/313227

Cited by 73 publications

(33 citation statements)

References 12 publications

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“…The efficiency and calibration during flight was also carefully monitored (Esposito et al 1999). Using Monte Carlo simulations the energy range was recently extended up to higher energies with a correspondingly larger uncertainty, mainly from the self-vetoing of the detector by the back-scattering from the electromagnetic calorimeter into the veto counters for high energetic showers (Strong et al 2004;Thompson et al 2005).…”

Section: Analysis Of Egret Datamentioning

confidence: 99%

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EGRET excess of diffuse galactic gamma rays as tracer of dark matter

Boer¹,

Sander²,

Жуков³

et al. 2005

A&A

137

213

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The public data from the EGRET space telescope on diffuse Galactic gamma rays in the energy range from 0.1 to 10 GeV are reanalyzed with the purpose of searching for signals of Dark Matter annihilation (DMA). The analysis confirms the previously observed excess for energies above 1 GeV in comparison with the expectations from conventional Galactic models. In addition, the excess was found to show all the key features of a signal from Dark Matter Annihilation (DMA): a) the excess is observable in all sky directions and has the same shape everywhere, thus pointing to a common source; b) the shape corresponds to the expected spectrum of the annihilation of non-relativistic massive particles into -among others -neutral π 0 mesons, which decay into photons. From the energy spectrum of the excess we deduce a WIMP mass between 50 and 100 GeV, while from the intensity of the excess in all sky directions the shape of the halo could be reconstructed. The DM halo is consistent with an almost spherical isothermal profile with substructure in the Galactic plane in the form of toroidal rings at 4 and 14 kpc from the center. These rings lead to a peculiar shape of the rotation curve, in agreement with the data, which proves that the EGRET excess traces the Dark Matter.

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Section: Analysis Of Egret Datamentioning

confidence: 99%

“…The EGRET detector was calibrated in a quasi mono-energetic gamma ray beam at SLAC, so its response is well known (Thompson et al 1987). Also the monitoring during the flight was done carefully (Esposito et al 1999).…”

Section: Possible Objections To the Dma Interpretationmentioning

confidence: 99%

EGRET excess of diffuse galactic gamma rays as tracer of dark matter

Boer¹,

Sander²,

Жуков³

et al. 2005

A&A

137

213

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“…The data were collected between 1991 April and 1995 September, in four observing cycles: cycle 1, 1991April to 1992cycle 2, 1992November to 1993cycle 3, 1993August to 1994cycle 4, 1994cycle 4, October to 1995 October. Each cycle is composed of several viewing periods (VPs), each lasting typically 14 d. The EGRET instrument (Kanbach et al 1988; Thompson et al 1993;Esposito et al 1999) detected γ -ray photons by means of a spark-chamber device filled with neon gas. Throughout the mission, the quality of the gas diminished, causing a decrease in EGRET detection capabilities.…”

Section: γ-R Ay Ag N S a M P L E 21 Egret Instrumentmentioning

confidence: 99%

On the duty-cycle of γ-ray blazars

Vercellone

Soldi

Chen

et al. 2004

Monthly Notices of the Royal Astronomical Society

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We study several properties of blazars detected in the γ‐ray energy range by comparing the Energetic Gamma Ray Experiment Telescope (EGRET) sources with a sample of radio blazars which can be considered possible γ‐ray candidates. We define three classes: non‐γ‐ray blazars, blazars with quasi‐steady γ‐ray emission and γ‐ray blazars with substantial activity level. We find that, on average, BL Lacertae objects show a relatively steady γ‐ray emission, when detected. On the other hand, most flat‐spectrum radio quasars (FSRQs) show substantial γ‐ray variability. We attribute a γ‐ray activity index ψ=ψ−7× 10−7 cm−2 s−1 to all EGRET blazars, and show that FSRQs dominate the sample with non‐zero ψ in the range 0 < ψ−7 < 0.035. By combining the information of detected and candidate active galactic nuclei, we characterize the blazar activity, including the discovery of a region of consistency between the γ‐ray flaring duty‐cycle and the recurrence time between flares. We also find a possible relation between the activity index of FSRQs and their black hole mass. More optical and γ‐ray data are crucially important to test this relation.

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“…The intensity spectrum has additional associated uncertainties, which arise from the subtraction of the extragalactic background and the sources. A systematical error of 10% is assumed to account for uncertainties in the spark chamber efficiency correction (Esposito et al 1999).…”

Section: Pion Source Spectrummentioning

confidence: 99%

Excess GeV radiation and cosmic ray origin

Büsching¹,

Pohl²,

Schlickeiser³

2001

A&A

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Abstract. Particle acceleration at supernova remnant (SNR) shock waves is regarded as the most probable mechanism for providing Galactic cosmic rays at energies below 10 15 eV. The Galactic cosmic ray hadron component would in this picture result from the injection of relativistic particles from many SNRs. It is well known that the superposition of individual power law source spectra with dispersion in the spectral index value, which behaviour is observed in the synchrotron radio spectra of shell SNR, displays a positive curvature in the total spectrum and in particular shows a hardening at higher energies. Recent observations made with the EGRET instrument on the Compton Gamma-Ray Observatory of the diffuse Galactic γ-ray emission reveal a spectrum which is incompatible with the assumption that the cosmic ray spectra measured locally hold throughout the Galaxy: the spectrum above 1 GeV, where the emission is supposedly dominated by π 0 -decay, is harder than that derived from the local cosmic ray proton spectrum. We demonstrate that in case of a SNR origin of cosmic ray nucleons part of this γ-ray excess may be attributed to the dispersion of the spectral indices in these objects. In global averages, as are γ-ray line-of-sight integrals, this dispersion leads to a positive curvature in the composite spectrum, and hence to modified π 0 -decay γ-ray spectra.

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In‐Flight Calibration of EGRET on the Compton Gamma‐Ray Observatory

Cited by 73 publications

References 12 publications

EGRET excess of diffuse galactic gamma rays as tracer of dark matter

EGRET excess of diffuse galactic gamma rays as tracer of dark matter

On the duty-cycle of γ-ray blazars

Excess GeV radiation and cosmic ray origin

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