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

Matsuura, M. ORCID:, Indebetouw, R, Woosley, S, Bujarrabal, V, Abellan, F. J., McCray, R., Kamenetzky, J., Fransson, C., Barlow, M. J., Gomez, H. L. ORCID:, Cigan, P., De Looze, I., Spyromilio, J., Staveley-Smith, L., Zanardo, G., Roche, P., Larsson, J., Viti, S., van Loon, J. Th., Wheeler, J. C., Baes, M., Chevalier, R., Lundqvist, P., Marcaide, J. M., Dwek, E., Meixner, M., Ng, C. -Y., Sonneborn, G. and Yates, J. 2017. ALMA spectral survey of Supernova 1987A – molecular inventory, chemistry, dynamics and explosive nucleosynthesis. Monthly Notices of the Royal Astronomical Society 469 (3) , pp. 3347-3362. 10.1093/mnras/stx830

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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.

Item Type: Article
Date Type: Publication
Status: Published
Schools: Physics and Astronomy
Subjects: Q Science > QB Astronomy
Uncontrolled Keywords: Supernovae: individual: Supernova 1987A, ISM: abundances, ISM: molecules, ISM: supernova remnants, radio lines: ISM
Publisher: Oxford University Press
ISSN: 0035-8711
Date of First Compliant Deposit: 12 April 2017
Date of Acceptance: 31 March 2017
Last Modified: 13 Nov 2023 17:08

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