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We report the first molecular line survey of Supernova 1987A in the millimetre wavelengthrange. In the Atacama Large Millimeter/submillimeter Array (ALMA) 210–300 and 340–360 GHz spectra, we detected cold (20–170 K) CO,28SiO, HCO+and SO, with weaker linesof29SiO from ejecta. This is the first identification of HCO+and SO in a young supernovaremnant. We find a dip in the J=6–5 and 5–4 SiO line profiles, suggesting that the ejectamorphology is likely elongated. The difference of the CO and SiO line profiles is consistent withhydrodynamic simulations, which show that Rayleigh–Taylor instabilities cause mixing of gas,with heavier elements much more disturbed, making more elongated structure. We obtainedisotopologue ratios of28SiO/29SiO>13,28SiO/30SiO>14 and12CO/13CO>21, with themost likely limits of28SiO/29SiO>128,28SiO/30SiO>189. Low29Si and30Si abundancesin SN 1987A are consistent with nucleosynthesis models that show inefficient formation ofneutron-rich isotopes in a low-metallicity environment, such as the Large Magellanic Cloud.The deduced large mass of HCO+(∼5×10−6M) and small SiS mass (<6×10−5M)might be explained by some mixing of elements immediately after the explosion. The mixingmight have caused some hydrogen from the envelope to sink into carbon- and oxygen-richzones after the explosion, enabling the formation of a substantial mass of HCO+. Oxygenatoms may have penetrated into silicon and sulphur zones, suppressing formation of SiS. OurALMA observations open up a new window to investigate chemistry, dynamics and explosivenucleosynthesis in supernovae., QC 20220201

Supernova (SN) 1987A has provided a unique opportunity to study how SN ejecta evolve in 30 years time scale. We report our ALMA spectral observations of SN 1987A, taken in 2014, 2015 and 2016, with detections of CO, 28SiO, HCO+ and SO, with weaker lines of 29SiO. We find a dip in the SiO line profiles, suggesting that the ejecta morphology is likely elongated. The difference of the CO and SiO line profiles is consistent with hydrodynamic simulations, which show that Rayleigh-Taylor instabilities causes mixing of gas, with heavier elements much more disturbed, making more elongated structure. Using 28SiO and its isotopologues, Si isotope ratios were estimated for the first time in SN 1987A. The estimated ratios appear to be consistent with theoretical predictions of inefficient formation of neutron rich atoms at lower metallicity, such as observed in the Large Magellanic Cloud (about half a solar metallicity). The deduced large HCO+ mass and small SiS mass, which are inconsistent to the predictions of chemical model, might be explained by some mixing of elements immediately after the explosion. The mixing might have made some hydrogen from the envelope to sink into carbon and oxygen-rich zone during early days after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may penetrate into silicon and sulphur zone, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive-nucleosynthesis in supernovae., QC 20190109

Most massive stars end their lives in core-collapse supernova explosions and enrich the interstellar medium with explosively nucleosynthesized elements. Following core collapse, the explosion is subject to instabilities as the shock propagates outward through the progenitor star. Observations of the composition and structure of the innermost regions of a core-collapse supernova provide a direct probe of the instabilities and nucleosynthetic products. SN 1987A in the Large Magellanic Cloud is one of very few supernovae for which the inner ejecta can be spatially resolved but are not yet strongly affected by interaction with the surroundings. Our observations of SN 1987A with the Atacama Large Millimeter/submillimeter Array are of the highest resolution to date and reveal the detailed morphology of cold molecular gas in the innermost regions of the remnant. The 3D distributions of carbon and silicon monoxide (CO and SiO) emission differ, but both have a central deficit, or torus-like distribution, possibly a result of radioactive heating during the first weeks ("nickel heating"). The size scales of the clumpy distribution are compared quantitatively to models, demonstrating how progenitor and explosion physics can be constrained., QC 20171205