Time evolution of the line emission from the inner circumstellar ring of SN 1987A and its hot spots

Abstract

We present seven epochs between October 1999 and November 2007 of high resolution VLT/UVES echelle spectra of the ejecta-ring collision of SN 1987A. The fluxes of most of the narrow lines from the unshocked gas decreased by a factor of 2-3 during this period, consistent with the decay from the initial ionization by the shock break-out. However, [O III] in particular shows an increase up to day ~6800. This agrees with radiative shock models where the pre-shocked gas is heated by the soft X-rays from the shock. The line emission from the shocked gas increases rapidly as the shock sweeps up more gas. We find that the neutral and high ionization lines follow the evolution of the Balmer lines roughly, while the intermediate ionization lines evolve less rapidly. Up to day ~6800, the optical light curves have a similar evolution to that of the soft X-rays. The break between day 6500 and day 7000 for [O III] and [Ne III] is likely due to recombination to lower ionization levels. Nevertheless, the evolution of the [Fe XIV] line, as well as the lines from the lowest ionization stages, continue to follow that of the soft X-rays, as expected. There is a clear difference in the line profiles between the low and intermediate ionization lines, and those from the coronal lines at the earlier epochs. This shows that these lines arise from regions with different physical conditions, with at least a fraction of the coronal lines coming from adiabatic shocks. At later epochs the line widths of the low ionization lines, however, increase and approach those of the high ionization lines of [Fe X-XIV]. The H-alpha line profile can be traced up to ~500 km/s at the latest epoch. This is consistent with the cooling time of shocks propagating into a density of (1-4)x10^4 cm-3.

25 Pages, 12 Figures, accepted for publication in A&A

References in corpus (9)

• The Triple-Ring Nebula around SN1987A: Fingerprint of a binary merger
• Infrared and X-Ray Evidence for Circumstellar Grain Destruction by the Blast Wave of Supernova 1987A
• Chandra LETG Observations of Supernova Remnant 1987A
• The Optical-Radio Mapping: the kinetic efficiency of Radio-Loud AGNs
• Chandra HETG Spectra of SN 1987A at 20 years
• Coronal emission from the shocked circumstellar ring of SN 1987A
• Fifteen Years of High-Resolution Radio Imaging of Supernova 1987A
• Chandra Observations of Supernova 1987A
• The Reverse Shock of SNR 1987A

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• Three-dimensional distribution of ejecta in Supernova 1987A at 10 000 days
• Emission lines due to ionizing radiation from a compact object in the remnant of Supernova 1987A
• The matter beyond the ring: the recent evolution of SN 1987A observed by the Hubble Space Telescope
• JWST NIRSpec observations of Supernova 1987A -- from the inner ejecta to the reverse shock
• Thermal Emission and Radioactive Lines, but No Pulsar, in the Broadband X-Ray Spectrum of Supernova 1987A
• Spectral Evolution of the X-Ray Remnant of SN 1987A: A High-Resolution $Chandra$ HETG Study
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• The morphology of the ejecta of SN 1987A at 31 years from 1150 to 10000 Å
• Near-infrared evolution of the equatorial ring of SN 1987A
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