HST-COS observations of hydrogen, helium, carbon, and nitrogen emission from the SN 1987A reverse shock

Kevin France, Richard McCray, Steven V. Penton, Robert P. Kirshner, Peter Challis, J. Martin Laming, Patrice Bouchet, Roger Chevalier, Peter M. Garnavich, Claes Fransson, Kevin Heng, Josefin Larsson, Stephen Lawrence, Peter Lundqvist, Nino Panagia, Chun S.J. Pun, Nathan Smith, Jesper Sollerman, George Sonneborn, Ben SugermanJ. Craig Wheeler

Research output: Contribution to journalArticle

23 Scopus citations

Abstract

We present the most sensitive ultraviolet observations of Supernova 1987A to date. Imaging spectroscopy from the Hubble Space Telescope-Cosmic Origins Spectrograph shows many narrow (Δv ∼ 300kms-1) emission lines from the circumstellar ring, broad (Δv ∼ 10-20 × 10 3kms-1) emission lines from the reverse shock, and ultraviolet continuum emission. The high signal-to-noise ratio (>40 per resolution element) broad Lyα emission is excited by soft X-ray and EUV heating of mostly neutral gas in the circumstellar ring and outer supernova debris. The ultraviolet continuum at λ > 1350 can be explained by H I two-photon (2s 2 S 1/2-1s 2 S 1/2) emission from the same region. We confirm our earlier, tentative detection of N V λ1240 emission from the reverse shock and present the first detections of broad He II λ1640, C IV λ1550, and N IV] λ1486 emission lines from the reverse shock. The helium abundance in the high-velocity material is He/H = 0.14 0.06. The N V/Hα line ratio requires partial ion-electron equilibration (Te/Tp ≈ 0.14-0.35). We find that the N/C abundance ratio in the gas crossing the reverse shock is significantly higher than that in the circumstellar ring, a result that may be attributed to chemical stratification in the outer envelope of the supernova progenitor. The N/C abundance may have been stratified prior to the ring expulsion, or this result may indicate continued CNO processing in the progenitor subsequent to the expulsion of the circumstellar ring.

Original languageEnglish (US)
Article number186
JournalAstrophysical Journal
Volume743
Issue number2
DOIs
StatePublished - Dec 20 2011

Keywords

  • circumstellar matter
  • shock waves
  • supernovae: individual (SN 1987A)

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    France, K., McCray, R., Penton, S. V., Kirshner, R. P., Challis, P., Martin Laming, J., Bouchet, P., Chevalier, R., Garnavich, P. M., Fransson, C., Heng, K., Larsson, J., Lawrence, S., Lundqvist, P., Panagia, N., Pun, C. S. J., Smith, N., Sollerman, J., Sonneborn, G., ... Craig Wheeler, J. (2011). HST-COS observations of hydrogen, helium, carbon, and nitrogen emission from the SN 1987A reverse shock. Astrophysical Journal, 743(2), [186]. https://doi.org/10.1088/0004-637X/743/2/186