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HST-COS OBSERVATIONS OF HYDROGEN, HELIUM, CARBON, AND NITROGEN EMISSION FROM THE SN 1987A REVERSE SHOCK.
- Source :
- Astrophysical Journal; Dec2011, Vol. 743 Issue 2, Special section p1-11, 11p
- Publication Year :
- 2011
-
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 ~ 300 km s<superscript>-1</superscript>) emission lines from the circumstellar ring, broad (Δv ~ 10-20 x 10³ km s<superscript>-1</superscript>) 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 Å can be explained by H I two-photon (2s ²S<subscript>1/2</subscript>-1s ²S<subscript>1/2</subscript>) emission from the same region. We confirm our earlier, tentative detection of N v λ 1240 emission from the reverse shock and present the first detections of broad He II λ 1640, C IV λ1550, and N IV] λ 1486 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 (T<subscript>e</subscript>/T<subscript>p</subscript> ≈ 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. [ABSTRACT FROM AUTHOR]
- Subjects :
- SUPERNOVAE
X-ray astronomy
HELIUM
CIRCUMSTELLAR matter
SHOCK waves
Subjects
Details
- Language :
- English
- ISSN :
- 0004637X
- Volume :
- 743
- Issue :
- 2
- Database :
- Complementary Index
- Journal :
- Astrophysical Journal
- Publication Type :
- Academic Journal
- Accession number :
- 71404953
- Full Text :
- https://doi.org/10.1088/0004-637X/743/2/186