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Published online by Cambridge University Press: 12 April 2016
G160.9+2.6 (HB9) is a supernova remnant of large angular diameter and low radio surface brightness. We report new observations of the continuum emission from HB9 at 408 MHz and 1420 MHz with angular resolutions of 3.5’ and 1.0#x2019;, respectively, which reveal significant filamentary structure not previously detected. The 1420 MHz field covers only the central and eastern parts of HB9. The 408-1420 MHz spectral index (S∝vα) of regions common to both maps is α=-0.68, with no significant spatial variation. The radio filamentary structure closely follows the optical structure. X-ray emission from HB9 is more centrally concentrated than the radio or optical emission. The radio, optical, and particularly, the X-ray surface brightness are all diminished in the northern and northwestern portions of the remnant, in directions approximately coincident with an extensive molecular cloud detected in CO.