EGRET Observations of Radio-bright Supernova Remnants

Esposito, J. A.; Hunter, S. D.; Kanbach, G.; Sreekumar, P.

doi:10.1086/177104

Cited by 253 publications

(286 citation statements)

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“…This amounts to an enhancement of the ion pressure by a factor of 1400 over ambient. From the review by Bloemen (1989) and models in Esposito et al (1996), we infer that this enhancement would lead to a gamma-ray production rate above 100 MeV, from no decay, of about 2.2 ] 10~22 photons s~1 per H atom in the shell. For a shell mass of about 450…”

Section: T He Gamma Raysmentioning

confidence: 96%

“…Claussen et al (1997) were further inÑuenced by the presence of an unidentiÐed EGRET gamma-ray source error circle overlapping the eastern limb of W44, suggesting that it may be due to cosmic rays from W44 interacting with an abutting dense cloud. The Wootten cloud is in fact projected on that location, and Esposito et al (1996) show that the source brightness, 50 ] 10~8 photons cm~2 s~1 above 100 MeV, would require a cosmic-ray intensity within the cloud nearly 100 times ambient, even if the entire cloud is being irradiated.…”

Section: Opticalmentioning

confidence: 99%

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Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Cox

Shelton

Maciejewski

et al. 1999

ApJ

165

222

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We show that many observations of W44, a supernova remnant in the Galactic plane at a distance of about 2500 pc, are remarkably consistent with the simplest realistic model. The model remnant is evolving in a smooth ambient medium of fairly high density, about 6 cm~3 on average, with a substantial density gradient. At the observed time it has an age of about 20,000 yr, consistent with the age of the associated pulsar, and a radius of 11È13 pc. Over most of the outer surface, radiative cooling has become important in the postshock gas ; on the denser end there has been sufficient compression of the cooled gas to develop a very thin dense half-shell of about 450 supported against further compression by M _ , nonthermal pressure. The half-shell has an expansion velocity of about 150 km s~1 and is bounded on the outer surface by a radiative shock with that speed. The deep interior of the remnant has a substantial and fairly uniform pressure, as expected from even highly idealized adiabatic models ; our model, however, is never adiabatic. Thermal conduction, while the remnant is young and hot, reduces the need for expansion cooling and prevents formation of the intensely vacuous cavity characteristic of adiabatic evolution. It radically alters the interior structure from what one might expect from familiarity with the Sedov solution. At the time of observation, the temperature in the center is about 6 ] 106 K, the density about 1 cm~3. The temperature decreases gradually away from the center, while the density rises. Farther out, where cooling is becoming important, the pressure drops precipitously, and the temperature in the denser gas there is quite low. We provide several analytic tools for the assembly of models of this type. We review the early evolution and shell formation analyses and their generalizations to evolution in a density gradient. We also calculate the density and temperature that should be present in the hot interior of a remnant with thermal conduction. We supply the van der Laan mechanism in a particularly useful form for the calculation of radio continuum from radiative remnants. Finally, we estimate the optical emission that should be present from Ñuorescence of UV light, emitted by the forming shell and the radiative shock and absorbed in the cold shell and the ambient medium, and the associated 63 km [O I] emission. Both are in agreement with the intensity and spatial structures found in recent observations. Neither requires interaction with a dense molecular cloud for its generation. We calculate the gamma rays that should be emitted by cosmic-ray electrons and ions in the shell, interacting with the cold material, and Ðnd each capable of generating about 25% of the Ñux reported by EGRET for the vicinity.

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Section: T He Gamma Raysmentioning

confidence: 96%

Section: Opticalmentioning

confidence: 99%

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Cox

Shelton

Maciejewski

et al. 1999

ApJ

165

222

View full text Add to dashboard Cite

show abstract

“…This mechanism is probably not the cause of the lower energy (rv 100 MeV-I GeV) "'I-ray emission that has been detected from supernova remnants by the EGRET experiment on CGRO (Esposito et al 1996). The identifications cannot be considered completely secure, but the association with remnants that appear to be interacting with dense gas (e.g., IC 443, W44) gives some confidence in the associations.…”

Section: Gamma-ray Emissionmentioning

confidence: 99%

“…The correlation between "'I-ray emission from a remnant and evidence for molecular cloud interaction (Esposito et al 1996) is generally expected because the high-energy emission should be stronger where interaction with a dense medium is taking place. The molecular cloud structure is expected to have dense, molecular clumps embedded within an interclump medium.…”

Section: Gamma-ray Emissionmentioning

confidence: 99%

High-energy Emission from Supernovae and Remnants

Chevalier

2000

Symp. - Int. Astron. Union

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Abstract.An early burst of energetic radiation is expected from a supernova at the time of shock breakout. This emission has not been directly observed but has been inferred from the photoionization around SN 1987A. X-ray emission has been detected from core-collapse supernovae in the days to years after the explosion as they interact with their circumstellar winds. Young Galactic supernova remnants provide the possibility of determining the composition structure of the ejecta through X-ray spectroscopy. An exciting finding for older remnants is that a number of remnants that appear to be interacting with molecular gas may be sources of high-energy ,-ray emission. The clumpy structure of molecular clouds has implications for the structure expected in high-energy emission. Finally, the field of ,-ray-line spectroscopy is beginning to yield results relevant to the explosive nucleosynthesis of radionuclides in supernovae.

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“…It is important to realize however that there is no evidence that TeV photons are the decay products of π 0 's. The sources of the cosmic rays have not been revealed by photon or proton astronomy [19,20,21,22]; see however reference [23].…”

Section: Amanda B10mentioning

confidence: 99%

High-Energy Neutrino Astronomy: Science and First Results

Halzen

2003

The Early Universe and the Cosmic Microwave Background: Theory and Observations

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Abstract.We introduce neutrino astronomy starting from the observational fact that Nature accelerates protons and photons to energies in excess of 10 20 and 10 13 eV, respectively. Although the discovery of cosmic rays dates back a century, we do not know how and where they are accelerated. We review the observations as well as speculations about the sources. Among these gamma ray bursts and active galaxies represent well-motivated speculations because these are also the sources of the highest energy gamma rays, with emission observed up to 20 TeV, possibly higher.We discuss why cosmic accelerators are expected to be cosmic beam dumps producing neutrino beams associated with the highest energy cosmic rays. Cosmic ray sources may produce neutrinos from MeV to EeV energy by a variety of mechanisms. The important conclusion is that, independently of the specific blueprint of the source, it takes a kilometer-scale neutrino observatory to detect the neutrino beam associated with the highest energy cosmic rays and gamma rays. The technology for commissioning such instrument has been established by the AMANDA detector at the South Pole. We review its performance and, with several thousand neutrinos collected, its first scientific results.

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EGRET Observations of Radio-bright Supernova Remnants

Cited by 253 publications

References 0 publications

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

Modeling W44 as a Supernova Remnant in a Density Gradient with a Partially Formed Dense Shell and Thermal Conduction in the Hot Interior. I. The Analytical Model

High-energy Emission from Supernovae and Remnants

High-Energy Neutrino Astronomy: Science and First Results

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