DISCOVERY OF X-RAY EMISSION FROM AND DISTANCE TO THE SUPERNOVA REMNANT G84.2-0.8

We analyze X-ray and radio observations of the supernova remnant G84.2-0.8. 1420 MHz atomic hydrogen (H I) line and radio continuum data yield Hi absorption spectra and a new Hi absorption distance of 5.8-6.2 kpc. Archival X-ray observations from ROSAT and Chandra which cover the area including G84.2-0.8 are analyzed to show extended X-ray emission from G84.2-0.8. Fits to X-ray spectra from Chandra, with the new Hi distance of 5.8-6.2 kpc, are used to determine the Sedov parameters of the supernova remnant. G84.2-0.8 is large (16-18 pc radius), middle aged (similar to 9000 yr), expanding in low-density interstellar medium (0.02 cm(-3)), and consistent with a low explosion energy (0.8-6.5 x 10(50) erg).