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Collisionless shock heating of heavy ions in SN 1987A


Astrophysical shocks at all scales, from those in the heliosphere up to cosmological shock waves, are typically ‘collisionless’, because the thickness of their jump region is much shorter than the collisional mean free path. Across these jumps, electrons, protons and ions are expected to be heated at different temperatures. Supernova remnants (SNRs) are ideal targets to study collisionless processes because of their bright post-shock emission and fast shocks, but the actual dependence of the post-shock temperature on the particle mass is still widely debated1. We tackle this longstanding issue through the analysis of deep multi-epoch and high-resolution observations, made with the Chandra X-ray telescope, of the youngest nearby supernova remnant, SN 1987A. We introduce a data analysis method by studying the observed spectra in close comparison with a dedicated full three-dimensional hydrodynamic simulation that self-consistently reproduces the broadening of the spectral lines of many ions together. We measure the post-shock temperature of protons and ions through comparison of the model with observations. Our results show that the ratio of ion temperature to proton temperature is always significantly higher than one and increases linearly with the ion mass for a wide range of masses and shock parameters.

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Fig. 1: Observed and synthetic maps and spectra of SN 1987A.
Fig. 2: Line broadening for selected ions in the X-ray spectra of SN 1987A.
Fig. 3: Modelled and measured Fe xvii line profile for 2011.
Fig. 4: Ion to proton temperature ratios measured by combining the 2007 and 2011 observations of SN 1987A for Ne, Mg, Si and Fe lines.

Data availability

The HD simulations adopted here are presented in detail in ref. 24. The Chandra dataset analysed are available in the Chandra Data Archive ( Other relevant data are available from the corresponding author upon reasonable request.


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The software used in this work was, in part, developed by the US Department of Energy-supported Advanced Simulation and Computing/Alliance Center for Astrophysical Thermonuclear Flashes at the University of Chicago. We acknowledge that the results of this research have been achieved using the PRACE Research Infrastructure resource MareNostrum III based in Spain at the Barcelona Supercomputing Center (PRACE Award no. 2012060993). The scientific results reported in this article are based to a significant degree on data obtained from the Chandra Data Archive. M.M., S.O., G.P. and F.B. acknowledge financial contribution from the agreement ASI-INAF n.2017-14-H.O. O.P. acknowledges partial support from the agreement 0118U004941.

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Authors and Affiliations



M.M. composed the text on the basis of inputs from all authors. M.M. designed the analysis procedure and led the analysis of the synthetic and actual X-ray spectra. S.O. led the set-up and run of the hydrodynamics simulation and the synthesis of X-ray spectra. D.N.B., K.A.F. and C.A. supported the X-ray data analysis process. F.R., G.P., O.P. and F.B. supported the analysis of the simulation and the synthesis of observables. All authors helped to discuss the results and to comment on the manuscript.

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Correspondence to Marco Miceli.

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Supplementary Information

Supplementary Figures 1–5, Supplementary Tables 1–2.

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Miceli, M., Orlando, S., Burrows, D.N. et al. Collisionless shock heating of heavy ions in SN 1987A. Nat Astron 3, 236–241 (2019).

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