2019ApJ...877...15G

We present a multiwavelength examination of the supernova remnant (SNR) S26 in the nearby galaxy NGC 300 using data from Chandra X-ray Observatory, XMM-Newton X-ray Observatory, Hubble Space Telescope (HST), the Very Large Array, and the Australia Telescope Compact Array. We simultaneously fit all of the available X-ray data with a thermal plasma model and find a temperature of 0.77 ± 0.13 keV with a hydrogen column density of (9.7_–4.8^+6.4) x 10²⁰ cm^–2. HST imaging allows us to measure a semimajor axis of 0.78 ± 0.10 arcsec (7.5±1.0 pc) and a semiminor axis of 0.69_–0.12^+0.14 arcsec (6.7_–1.4^+1.2 pc). This precise size helps to constrain the age and velocity of the shock to be (3.3_–0.6^+0.7) x 10³ yr and 411_–122⁺²⁷⁵ km s^–1. We also fit photometry of the surrounding stars to infer the age and mass of the progenitor star to be 8 ± 1 Myr and 25_–5⁺¹M_☉. Based on measured radio properties of the source and assuming equipartition, the estimated radio luminosity of ∼1.7 x 10³⁴ erg s^–1 over the 10⁸-10¹¹ Hz frequency range results in a minimum magnetic field associated with this SNR of 0.067 mG and the minimum energy needed to power the observed synchrotron emission of 1.5 x 10⁴⁹ erg. The size and temperature of N300-S26 appear to be similar to the Galactic SNR G311.5-0.3 except that G311.5-0.3 has a significantly lower X-ray luminosity, is older, and has a slower shock velocity.