We measure the expansion of the forward shock of the Small Magellanic Cloud supernova remnant 1E 0102.2-7219 in X-rays using Chandra X-Ray Observatory on-axis Advanced CCD Imaging Spectrometer observations from 1999 to 2016. We estimate an expansion rate of 0.025% ± 0.006% yr-1 and a blast wave velocity of (1.61 /- 0.37)× {10}3 {km} {{{s}}}-1. Assuming partial electron- ion equilibration via Coulomb collisions and cooling due to adiabatic expansion, this velocity implies a post-shock electron temperature of 0.84 ± 0.20 keV, which is consistent with the estimate of 0.68 ± 0.05 keV based on the X-ray spectral analysis. We combine the expansion rate with the blast wave and reverse shock radii to generate a grid of one- dimensional models for a range of ejecta masses (2{--}6 {M}☉ ) to constrain the explosion energy, age, circumstellar density, swept-up mass, and unshocked-ejecta mass. We find acceptable solutions for a constant-density ambient medium and for an r -2 power- law profile (appropriate for a constant progenitor stellar wind). For the constant-density case, we find an age of ∼1700 yr, explosion energies (0.87-2.61) × 1051 erg, ambient densities 0.85-2.54 amu cm-3, swept-up masses 22{--}66 {M}☉ , and unshocked-ejecta masses 0.05{--}0.16 {M}☉ . For the power-law density profile, we find an age of ∼2600 yr, explosion energies (0.34-1.02) × 1051 erg, densities 0.22{--}0.66 {amu} {cm}}-3 at the blast wave, swept-up masses 17{--}52 {M}☉ , and unshocked-ejecta masses 0.06{--}0.18 {M}☉ . Assuming that the true explosion energy was (0.5-1.5) × 1051 erg, ejecta masses 2{--}3.5 {M}☉ are favored for the constant-density case and 3{--}6 {M}☉ for the power-law case. The unshocked-ejecta mass estimates are comparable to Fe masses expected in core-collapse supernovae with progenitor mass 15.0{--}40.0 {M}☉ , offering a possible explanation for the lack of Fe emission observed in X-rays.
We measure the expansion of the forward shock of the Small Magellanic Cloud supernova remnant 1E 0102.2-7219 in X-rays using Chandra X-Ray Observatory on-axis Advanced CCD Imaging Spectrometer observations from 1999 to 2016. We estimate an expansion rate of 0.025%25 ± 0.006%25 yr-1 and a blast wave velocity of (1.61+/- 0.37)× {10}3 {km} {{{s}}}-1. Assuming partial electron- ion equilibration via Coulomb collisions and cooling due to adiabatic expansion, this velocity implies a post-shock electron temperature of 0.84 ± 0.20 keV, which is consistent with the estimate of 0.68 ± 0.05 keV based on the X-ray spectral analysis. We combine the expansion rate with the blast wave and reverse shock radii to generate a grid of one- dimensional models for a range of ejecta masses (2{--}6 {M}? ) to constrain the explosion energy, age, circumstellar density, swept-up mass, and unshocked-ejecta mass. We find acceptable solutions for a constant-density ambient medium and for an r -2 power- law profile (appropriate for a constant progenitor stellar wind). For the constant-density case, we find an age of ~1700 yr, explosion energies (0.87-2.61) × 1051 erg, ambient densities 0.85-2.54 amu cm-3, swept-up masses 22{--}66 {M}? , and unshocked-ejecta masses 0.05{--}0.16 {M}? . For the power-law density profile, we find an age of ~2600 yr, explosion energies (0.34-1.02) × 1051 erg, densities 0.22{--}0.66 {amu} {cm}}-3 at the blast wave, swept-up masses 17{--}52 {M}? , and unshocked-ejecta masses 0.06{--}0.18 {M}? . Assuming that the true explosion energy was (0.5-1.5) × 1051 erg, ejecta masses 2{--}3.5 {M}? are favored for the constant-density case and 3{--}6 {M}? for the power-law case. The unshocked-ejecta mass estimates are comparable to Fe masses expected in core-collapse supernovae with progenitor mass 15.0{--}40.0 {M}? , offering a possible explanation for the lack of Fe emission observed in X-rays.
