2019ApJ...881...85S

RX J0046.5-7308 is a shell-type supernova remnant (SNR) in the Small Magellanic Cloud (SMC). We carried out new ¹²CO(J = 1-0, 3-2) observations toward the SNR using Mopra and the Atacama Submillimeter Telescope Experiment. We found eight molecular clouds (A-H) along the X-ray shell of the SNR. The typical cloud size and mass are ∼10-15 pc and ∼1000-3000 M_☉, respectively. The X-ray shell is slightly deformed and has the brightest peak in the southwestern shell where two molecular clouds A and B are located. The four molecular clouds A, B, F, and G have high intensity ratios of ¹²CO(J = 3-2)/¹²CO(J = 1-0) > 1.2, which are not attributable to any identified internal infrared sources or high-mass stars. The H I cavity and its expanding motion are found toward the SNR, which are likely created by strong stellar winds from a massive progenitor. We suggest that the molecular clouds A-D, F, and G and H I clouds within the wind-blown cavity at V_LSR = 117.1-122.5 km s^–1 are associated with the SNR. The X-ray spectroscopy reveals the dynamical age of 26000_–2000⁺¹⁰⁰⁰ yr and the progenitor mass of >=30 M_☉, which is also consistent with the proposed scenario. We determine physical conditions of the giant molecular cloud LIRS 36A using the large velocity gradient analysis with archival data sets of the Atacama Large Millimeter/submillimeter Array; the kinematic temperature is 72_–37⁺⁵⁰ K and the number density of molecular hydrogen is 1500_–300⁺⁶⁰⁰ cm^–3. The next generation of γ-ray observations will allow us to study the pion-decay γ-rays from the molecular clouds in the SMC SNR.