TITLE:
Distances and Evolutionary States of Supernova Remnant G18.9-1.1 and Candidate G28.6+0.0
AUTHORS:
Sujith Ranasinghe, Denis Leahy, Wenwu Tian
KEYWORDS:
Supernova Remnants, Radio Continuum, Radio Lines
JOURNAL NAME:
Journal of High Energy Physics, Gravitation and Cosmology,
Vol.6 No.1,
November
19,
2019
ABSTRACT: 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 Mʘ,
typical of Type Ia SNe, or ~4700 yr if the ejecta mass is 5 Mʘ 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.