A multi-frequency study of the spectral index distribution in the SNR CTB 80

Abstract

We have conducted a study at radio wavelengths of the spectral behaviour of the supernova remnant (SNR) CTB 80. Based on an homogenised data set of integrated flux densities, we calculated for the whole SNR a radio index -0.36 +/- 0.02. The shape of the global spectrum suggests absorption by ionized gas in the interstellar medium (ISM) along the line of sight. Spatial spectral variations across the SNR are investigated based on high-angular resolution data at 240, 324, 610, and 1380 MHz using different techniques. The three extended arms associated with this SNR, show a clear indication of spectral steepening when moving outwards from the central nebula, with variations of up to - 0.9. However, while the spectral steepening is smooth along the eastern arm, the northern and soutwestern arms include locally flatter structures, which in all cases coincide with radio, IR, and optical emission enhancements. We interpret this spectral property as the result of the combination of two different particle populations: aging relativistic electrons injected by PSR B1951+32 and particles accelerated at the sites where the SNR shock front encounters interstellar gas inhomogeneities. Concerning the central nebula, the angular resolution of the available database does not permit a detailed spectral study of the core region, i.e. the 45'' region around PSR B1951+32, where we can only confirm an average spectral index alpha=0.0. The surrounding 8' plateau nebula has an <alpha> ~ -0.25, with a peak of alpha ~ -0.29 coincident with a secondary maximun located at the termination of a twisted filament that trails to the east, behind the pulsar.

arXiv comment7 pages, 6 figures

References in corpus (5)

• WHAM Observations of H-Alpha, [S II], and [N II] toward the Orion and Perseus Arms: Probing the Physical Conditions of the Warm Ionized Medium
• Proper Motion Measurements of Pulsar B1951+32 in the Supernova Remnant CTB 80
• Spatially-resolved Thermal Continuum Absorption against the Supernova Remnant W49B
• New high-resolution radio observations of the SNR CTB 80
• The peculiar supernova remnant CTB 80

Cited by in corpus (7)

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• On the radio spectra of supernova remnants
• A Sino-German $\lambda$6\ cm polarization survey of the Galactic plane. V. Large supernova remnants
• Maximally-hard spectra from diffusive shock-acceleration in pulsar-wind nebulae
• A polarization study of the supernova remnant CTB 80
• A source of gamma rays coincident with the shell of the supernova remnant CTB 80