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ALMA spectral survey of Supernova 1987A-molecular inventory, chemistry, dynamics and explosive nucleosynthesis

Van Loon

ALMA spectral survey of Supernova 1987A-molecular inventory, chemistry, dynamics and explosive nucleosynthesis Thumbnail


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Abstract

We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. 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 lines of 29SiO from ejecta. This is the first identification of HCO+ and SO in a young supernova remnant. We find a dip in the J = 6–5 and 5–4 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 cause mixing of gas, with heavier elements much more disturbed, making more elongated structure. We obtained isotopologue ratios of 28SiO/29SiO?> 13, 28SiO/30SiO?> 14 and 12CO/13CO > 21, with the most likely limits of 28SiO/29SiO >128, 28SiO/30SiO >189. Low 29Si and 30Si abundances in SN 1987A are consistent with nucleosynthesis models that show inefficient formation of neutron-rich isotopes in a low-metallicity environment, such as the Large Magellanic Cloud. The deduced large mass of HCO+ (~5 × 10-6?M?) and small SiS mass (<6 × 10-5?M?) might be explained by some mixing of elements immediately after the explosion. The mixing might have caused some hydrogen from the envelope to sink into carbon- and oxygen-rich zones after the explosion, enabling the formation of a substantial mass of HCO+. Oxygen atoms may have penetrated into silicon and sulphur zones, suppressing formation of SiS. Our ALMA observations open up a new window to investigate chemistry, dynamics and explosive nucleosynthesis in supernovae.

Citation

Van Loon. (2017). ALMA spectral survey of Supernova 1987A-molecular inventory, chemistry, dynamics and explosive nucleosynthesis. Monthly Notices of the Royal Astronomical Society, 3347 -3362. https://doi.org/10.1093/mnras/stx830

Acceptance Date Mar 31, 2017
Publication Date Aug 11, 2017
Journal Monthly Notices of the Royal Astronomical Society
Print ISSN 0035-8711
Publisher Oxford University Press
Pages 3347 -3362
DOI https://doi.org/10.1093/mnras/stx830
Keywords supernovae, individual, Supernova 1987A, ISM, abundances, ISM, molecules, ISM, supernova remnants, radio lines, ISM
Publisher URL https://doi.org/10.1093/mnras/stx830

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