Author(s)

Sujith Ranasinghe^1*, Denis Leahy¹, Wenwu Tian^1,2

¹Department of Physics & Astronomy, University of Calgary, Calgary, Canada.
²National Astronomical Observatories, CAS, Beijing, China.

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 ¹³CO emission spectra and to spectra of HII regions in the area to determine kinematic distances. G18.9-1.1 is at 2.1 ± 0.4 kpc and G28.6+0.0 is at 9.0 ± 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 ≈3 × 10⁵⁰ erg and is in a low-density region of the ISM, ~0.1 cm^-3. It has age ~3700 yr if the ejecta mass is 1.4 M_ʘ, typical of Type Ia SNe, or ~4700 yr if the ejecta mass is 5 M_ʘ 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^-3 but could be as old as ~6000 yr if the ISM density is as high as 100 cm^-3.

Supernova Remnants, Radio Continuum, Radio Lines

Ranasinghe, S. , Leahy, D. and Tian, W. (2020) Distances and Evolutionary States of Supernova Remnant G18.9-1.1 and Candidate G28.6+0.0. Journal of High Energy Physics, Gravitation and Cosmology, 6, 9-19. doi: 10.4236/jhepgc.2020.61002.