Distance and Evolutionary States of Supernova Remnant G18.9-1.1 and Candidate G28.6+0.0

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 ${}^{13}$CO emission spectra and to spectra of HII regions in the area to determine kinematic distances. G18.9-1.1 is at 2.1$\pm$0.4 kpc and G28.6+0.0 is at 9.0$\pm$0.3 kpc from the Sun. Using 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 a low, but not atypical, explosion energy of $\simeq$3$\times$10${}^{50}$ erg and is in a low density region of the ISM, $\simeq$0.1 cm${}^{-3}$. It has age $\simeq$3700 yr if the ejecta mass is 1.4 M${}_{\odot }$, typical of Type Ia SNe, or $\simeq$4700 yr if the ejecta mass is 5 M${}_{\odot }$ 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 $\simeq$600 yr if the ISM density is 1 cm${}^{-3}$ but could be as old as $\simeq$6000 yr if the ISM density is as high as 100 cm${}^{-3}$.

11 pages, 6 figures

References in corpus (4)

• The Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• The VLA Galactic Plane Survey
• Galactic Supernova Remnant Candidates Discovered by THOR
• Energetics and Birth Rates of Supernova Remnants in the Large Magellanic Cloud

Cited by in corpus (2)

• Distances, Radial Distribution and Total Number of Galactic Supernova Remnants
• Searches for continuous gravitational waves from young supernova remnants in the early third observing run of Advanced LIGO and Virgo