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A&A Supplement series, Vol. 123, June I 1997, 199-207

Received January 19; accepted September 11, 1996

The unusual supernova remnant G76.9+1.0: The low-frequency radio spectrum

T.L. Landeckertex2html_wrap1384 - Y. Zhengtex2html_wrap1386 - X. Zhangtex2html_wrap1388 - L.A. Higgstex2html_wrap1390

Send offprint request: T.L. Landecker

tex2html_wrap1392  Dominion Radio Astrophysical Observatory, National Research Council, Box 248, Penticton, British Columbia V2A 6K3, Canada
tex2html_wrap1394  Beijing Astronomical Observatory, Chinese Academy of Sciences, Beijing 100080, China


G76.9+1.0 is an unusual radio source which is interpreted as a filled-centre supernova remnant (SNR). New 232-MHz observations of a field containing G76.9+1.0 have been combined with a re-analysis of existing observational data to derive the low-frequency spectrum of the SNR. Its spectral index has a value of about 0.6 above 1 GHz, and appears to flatten below that frequency. This may indicate a ``break'' in the spectrum below 1 GHz. However, further observations at frequencies below 400 MHz will be required before this can be firmly established. The low-frequency spectra of several other radio sources in the field surrounding G76.9+1.0 were also derived, partially to confirm the validity of the 232-MHz flux densities but also to provide new lower frequency data for these objects. They include several HII  regions and some extragalactic sources. Two of the latter have rather steep spectra and merit further study.

keywords: ISM: supernova remnants -- ISM: individual objects: G76.9+1.0 -- radio continum: ISM -- radio continum: general

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