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arXiv · 1704.02324

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

M. Matsuura·R. Indebetouw·S. Woosley·V. Bujarrabal·F. J. Abellan·R. McCray·J. Kamenetzky·C. Fransson·M. J. Barlow·H. L. Gomez·P. Cigan·I De Looze·J. Spyromilio·L. Staveley-Smith·G. Zanardo·P. Roche·J. Larsson·S. Viti·J. Th. van Loon·J. C. Wheeler·M. Baes·R. Chevalier·P. Lundqvist·J. M. Marcaide·E. Dwek·M. Meixner·C. -Y. Ng·G. Sonneborn·J. Yates
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Abstract

We report the first molecular line survey of Supernova 1987A in the millimetre wavelength range. In the 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+ (~5x10^-6 Msun) and small SiS mass (<6x10^-5 Msun) 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.

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M. Matsuura, R. Indebetouw, S. Woosley, V. Bujarrabal, F. J. Abellan, R. McCray, J. Kamenetzky, C. Fransson, M. J. Barlow, H. L. Gomez, P. Cigan, I De Looze, J. Spyromilio, L. Staveley-Smith, G. Zanardo, P. Roche, J. Larsson, S. Viti, J. Th. van Loon, J. C. Wheeler, M. Baes, R. Chevalier, P. Lundqvist, J. M. Marcaide, E. Dwek, M. Meixner, C. -Y. Ng, G. Sonneborn, J. Yates. 2017-04-07. ALMA spectral survey of Supernova 1987A --- molecular inventory, chemistry, dynamics and explosive nucleosynthesis. https://doi.org/10.1093/mnras%2Fstx830

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