Supplement to the Second EGRET Catalog of High-Energy Gamma-Ray Sources

Thompson, D. J.; Bertsch, D. L.; Dingus, B. L.; Esposito, J. A.; Artigau, Étienne; Fichtel, C. E.; Friedlander, D. P.; Hartman, R. C.; Hunter, S. D.; Kendig, D. J.; Mattox, J. R.; McDonald, L. M.; Mukherjee, R.; Ramanamurthy, P. V.; Sreekumar, P.; Montigny, C. von; Fierro, J. M.; Jones, B. B.; Lin, Y. C.; Michelson, P. F.; Nolan, P. L.; Tompkins, W. F.; Willis, T. D.; Kanbach, G.; Mayer‐Hasselwander, H. A.; Merck, M.; Pohl, M.; Kniffen, D. A.; Schneid, E. J.

doi:10.1086/192362

Cited by 105 publications

(37 citation statements)

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“…The 95% confidence contour for this γ-ray source coincides with the southeastern sector of the remnant (Thompson et al 1996). de Jager & Mastichiadis (1997) explained the observed GeV γ-rays in terms of relativistic bremsstrahlung and inverse Compton scattering produced by a power-law distribution of relativistic electrons injected by the pulsar PSR B1853+01.…”

Section: Introductionmentioning

confidence: 62%

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz

Castelletti

Dubner

Brogan

et al. 2007

A&A

108

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Aims. We present new Very Large Array (VLA) radio images at 74 and 324 MHz of the SNR W44. The VLA images, obtained with unprecedented angular resolution and sensitivity for such low frequencies (HPBW 37 at 74 MHz, and 13 at 324 MHz), have been used in combination with existing 1442 MHz radio data, Spitzer IR data, and ROSAT and Chandra X-ray data to investigate morphological and spectral continuum properties of this SNR. Methods. The observations were carried out with the VLA simultaneously at 74 and 324 MHz in the A and B configurations and at 324 MHz in the C and D configurations. The radio continuum spectral index distribution was derived through direct comparison of the combined data at 74, 324, and 1442 MHz. In addition, to isolate and identify different spectral components, tomographic spectral analysis was performed. Results. We measured total flux densities of 634 Jy and 411 Jy at 74 and 324 MHz, respectively, for W44, and from a careful assessment of published values between 22 and 10 700 MHz derived a global integrated continuum spectral index α = −0.37 ± 0.02. The spatially resolved spectral index study revealed that the bright filaments, both around and across the SNR, have a straight spectrum between 74 and 1442 MHz, with α ∼ −0.5, with two clear exceptions: a short portion of the SNR limb to the southeast, with α varying between 0 and +0.4 and a bright arc to the west where the spectrum breaks around 300 MHz and becomes concave down. We conclude that at the shell and along the internal filaments, the electrons responsible for the synchrotron emission were accelerated at the shock according to a simple diffusive shock model. The positive spectrum corresponds to a location where the SN shock is running into a molecular cloud and the line of sight intersects the photo dissociation region of an HII region and a young stellar object is present. Such spectral inversion is a classic signature of thermal absorption, either from ionized gas in the postshock region, from the HII region itself, or both. The curved spectrum on the westernmost bright arc is explained as the consequence of strong post-shock densities and enhanced magnetic fields after the interaction of the SN shock with a coincident molecular cloud. No spectral index trace was found indicating any connection between the associated pulsar PSR B1953+0.1 and the surrounding shell, nor between the SNR and the 3EG 1853+0114 γ-ray source proposed to be associated with W44. The comparison of the 324 MHz image with a 4.5 µm IR image obtained with Spitzer underscored an impressive correspondence between emission both to the north and west sides of W44, while the comparison with ROSAT and Chandra images confirm that the synchrotron radio emission surrounds the thermal X-ray radiation.

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Section: Introductionmentioning

confidence: 62%

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz

Castelletti

Dubner

Brogan

et al. 2007

A&A

108

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“…b Flux density. EGRET flux conversion follows Thompson et al (1996). Optical-to-X-ray data are corrected for Galactic extinction.…”

Section: X-raysmentioning

confidence: 99%

Broad-band continuum and line emission of theγ-ray blazar PKS 0537–441

Pian

Falomo

Hartman

et al. 2002

A&A

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Abstract. PKS 0537-441, a bright γ-ray emitting blazar, was observed at radio, optical, UV and X-ray frequencies during various EGRET pointings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all wavelengths. BeppoSAX observations made in 1998, non-simultaneously with exposures at other frequencies, allow us to characterize precisely the spectral shape of the high energy blazar component, which we attribute to inverse Compton scattering. The optical-to-γ-ray spectral energy distributions at the different epochs show that the γ-ray luminosity dominates the bolometric output. This, together with the presence of optical and UV line emission, suggests that, besides the synchrotron self-Compton mechanism, the Compton upscattering of photons external to the jet (e.g., in the broad line region) may have a significant role in the production of high energy radiation. The multiwavelength variability can be reproduced by changes of the plasma bulk Lorentz factor. The spectrum secured by IUE in 1995 appears to be partially absorbed shortward of ∼1700 Å. However, this signature is not detected in the HST spectrum taken during a lower state of the source. The presence of intervening absorbers is not supported by optical imaging and spectroscopy of the field.

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“…In particular, CGRO hosted the Energetic Gamma-Ray Experiment Telescope (EGRET) (operating in the energy range 30 MeV-30 GeV) which carried out a complete sky survey that detected hundreds of gamma-ray sources (Fichtel & Trombka 1997;Hartman et al 1999; Thompson et al 1993Thompson et al , 1995Thompson et al , 1996Thompson et al , 1998.…”

Section: Introductionmentioning

confidence: 99%

The AGILE Mission

Tavani

Barbiellini

Argan³

et al. 2009

A&A

349

225

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Context. AGILE is an Italian Space Agency mission dedicated to observing the gamma-ray Universe. The AGILE's very innovative instrumentation for the first time combines a gamma-ray imager (sensitive in the energy range 30 MeV-50 GeV), a hard X-ray imager (sensitive in the range 18-60 keV), a calorimeter (sensitive in the range 350 keV-100 MeV), and an anticoincidence system. AGILE was successfully launched on 2007 April 23 from the Indian base of Sriharikota and was inserted in an equatorial orbit with very low particle background. Aims. AGILE provides crucial data for the study of active galactic nuclei, gamma-ray bursts, pulsars, unidentified gamma-ray sources, galactic compact objects, supernova remnants, TeV sources, and fundamental physics by microsecond timing.Methods. An optimal sky angular positioning (reaching 0.1 degrees in gamma-rays and 1-2 arcmin in hard X-rays) and very large fields of view (2.5 sr and 1 sr, respectively) are obtained by the use of Silicon detectors integrated in a very compact instrument. Results. AGILE surveyed the gamma-ray sky and detected many Galactic and extragalactic sources during the first months of observations. Particular emphasis is given to multifrequency observation programs of extragalactic and galactic objects. Conclusions. AGILE is a successful high-energy gamma-ray mission that reached its nominal scientific performance. The AGILE Cycle-1 pointing program started on 2007 December 1, and is open to the international community through a Guest Observer Program.

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Supplement to the Second EGRET Catalog of High-Energy Gamma-Ray Sources

Cited by 105 publications

References 0 publications

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz

The low-frequency radio emission and spectrum of the extended SNR W44: new VLA observations at 74 and 324 MHz

Broad-band continuum and line emission of theγ-ray blazar PKS 0537–441

The AGILE Mission

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