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          Institute: MPI für extraterrestrische Physik     Collection: High Energy Astrophysics at MPE     Display Documents

ID: 5821.0, MPI für extraterrestrische Physik / High Energy Astrophysics at MPE
X-ray spectrum of supernova remnant 1987A
Authors:Michael, Eli; Zhekov, Svetozar; McCray, Richard; Hwang, Una; Burrows, David N.; Park, Sangwook; Garmire, Gordon P.; Holt, Stehpen S.; Hasinger, Günther
Date of Publication (YYYY-MM-DD):2002-07-20
Title of Journal:The Astrophysical Journal
Journal Abbrev.:Astrophys. J.
Issue / Number:1
Start Page:166
End Page:178
Review Status:Peer-review
Audience:Experts Only
Abstract / Description:We discuss the X-ray emission observed from supernova remnant 1987A with the Chandra X-Ray Observatory. We analyze a high- resolution spectrum obtained in 1999 October with the high- energy transmission grating (HETG). From this spectrum we measure the strengths and an average pro le of the observed X- ray lines. We also analyze a high signal-to-noise ratio CCD spectrum obtained in 2000 December. The good statistics (approximate to9250 counts) of this spectrum and the high spatial resolution provided by the telescope allow us to perform spectroscopic analyses of different regions of the remnant. We discuss the relevant shock physics that can explain the observed X-ray emission. The X-ray spectra are well fitted by plane-parallel shock models with postshock electron temperatures of approximate to2.6 keV and ionization ages of approximate to6 x 10(10) cm(-3) s. The combined X-ray line pro le has a FWHM of approximate to5000 km s(-1), indicating a blast-wave speed of approximate to3500 km s(-1). At this speed, plasma with a mean postshock temperature of approximate to17 keV is produced. This is direct evidence for incomplete electron-ion temperature equilibration behind the shock. Assuming this shock temperature, we constrain the amount of collisionless electron heating at the shock front at T-e0/T-s = 0.11(-0.01)(+0.02). We find that the plasma has low metallicity (abundances are approximate to0.1-0.4 solar) and is nitrogen enriched (N/O approximate to 0.8 by number), similar to abundances found for the equatorial ring. Analysis of the spectra from different regions of the remnant reveals slight differences in the parameters of the emitting plasma. The plasma is cooler near the optical spot 1 (at position angle approximate to30degrees) and in the eastern half of the remnant, where the bright optical spots are found, than in the western half, consistent with the presence of slower (approximate to500 km s(-1)) shocks entering denser ring material. There is an overall flux asymmetry between the two halves, with the eastern half being 15%-50% brighter (depending on how the center of the remnant is defined). However, our spectroscopic analysis shows that less than 5% of the overall X-ray emission could come from a slow shock component. Therefore the flux asymmetry cannot fully be due to X-rays produced by the blast wave entering the ring, but rather indicates an asymmetry in the global interaction with the circumstellar material interior to the ring.
Free Keywords:shock waves; supernova remnants; supernovae : individual (SN 1987A); X-rays : ISM
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für extraterrestrische Physik
External Affiliations:Univ Colorado, JILA, Campus Box 440, Boulder, CO 80309 USA; Univ Colorado, JILA, Boulder, CO 80309 USA; NASA, Goddard Space Flight Ctr, Greenbelt, MD 20771 USA; Penn State Univ, Dept Astron & Astrophys, Davey Lab 525, University Pk, PA 16802 USA; FW Olin Coll Engn, Needham, MA 02492 USA; Max Planck Inst Extraterr Phys, D-85748 Garching, Germany
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