The X-ray Spectrum of Supernova Remnant 1987A

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 profile of the observed X-ray lines. We also analyze a high signal-to-noise ratio CCD spectrum obtained in 2000 December. The good statistics (≈ 9250 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 fit by plane parallel shock models with postshock electron temperatures of ≈ 2.6 keV and ionization ages of ≈ 6×10 cm s. The combined X-ray line profile has a FWHM of ≈ 5000 km s, indicating a blast wave speed of≈ 3500 km s. At this speed, plasma with a mean post-shock temperature of ≈ 17 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 Te0/Ts = 0.11 +0.02 −0.01. We find that the plasma has low metallicity (abundances are ≈ 0.1 – 0.4 solar) and is nitrogen enriched (N/O ≈ 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 JILA, University of Colorado, Campus Box 440, Boulder, CO 80309-0440; [email protected]. On leave from Space Research Institute, Sofia, Bulgaria. NASA Goddard Space Flight Center, Code 662, Greenbelt, MD 20771. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802. F. W. Olin College of Engineering, Needham, MA 02492 Max-Planck-Institut für Extraterrestrische Physik, Postfach 1312, D-85748 Garching, Germany.