%0 Journal Article
%T Distances and Evolutionary States of Supernova Remnant G18.9-1.1 and Candidate G28.6+0.0
%A Sujith Ranasinghe
%A Denis Leahy
%A Wenwu Tian
%J Journal of High Energy Physics, Gravitation and Cosmology
%P 9-19
%@ 2380-4335
%D 2020
%I Scientific Research Publishing
%R 10.4236/jhepgc.2020.61002
%X HI
spectra of the supernova remnant G18.9-1.1 and the supernova remnant candidate
G28.6+0.0 are analyzed. We compared the spectra to <sup>13</sup>CO emission
spectra and to spectra of HII regions in the area to
determine kinematic distances. G18.9-1.1 is at 2.1 ¡À 0.4 kpc and G28.6+0.0 is
at 9.0 ¡À 0.3 kpc from the Sun. Using the published X-ray spectra of G18.9-1.1,
we apply supernova remnant models for shocked-ISM temperature and emission measure.
We find that G18.9-1.1 has low, but not atypical, explosion energy of ¡Ö3 ¡Á 10<sup>50</sup> erg and is in a low-density region of the ISM, ~0.1 cm<sup>-3</sup>. It has age
~3700 yr if the ejecta mass is 1.4 M<sub>&#664;</sub>,
typical of Type Ia SNe, or ~4700 yr if the ejecta mass is 5 M<sub>&#664;</sub> typical of core-collapse SN. The candidate G28.6+0.0 does not have reported
X-ray emission, so we apply a basic Sedov model. The Sedov age is ~600 yr if
the ISM density is 1 cm<sup>-3</sup> but could be as old as ~6000 yr if the ISM
density is as high as 100 cm<sup>-3</sup>.
%K Supernova Remnants
%K Radio Continuum
%K Radio Lines
%U http://www.scirp.org/journal/PaperInformation.aspx?PaperID=96436