Chandra HETG Spectra of SN 1987A at 20 years

We have undertaken deep, high-resolution observations of SN 1987A at ~20 years after its explosion with the Chandra HETG and LETG spectrometers. Here we present the HETG X-ray spectra of SN 1987A having unprecedented spectral resolution and signal-to-noise in the 6 A to 20 A bandpass, which includes the H-like and He-like lines of Si, Mg, Ne, as well as O VIII lines and bright Fe XVII lines. In joint analysis with LETG data, we find that there has been a significant decrease from 2004 to 2007 in the average temperature of the highest temperature component of the shocked-plasma emission. Model fitting of the profiles of individual HETG lines yields bulk kinematic velocities of the higher-Z ions, Mg and Si, that are significantly lower than those inferred from the LETG 2004 observations.