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X-ray Kinematics and Infrared Spectroscopic Studies of Supernova Remnants

Presentation #133.04D in the session Planetary Nebulae, Supernova Remnants.

Published onJun 29, 2022
X-ray Kinematics and Infrared Spectroscopic Studies of Supernova Remnants

We present the results of our X-ray ejecta kinematic study of Kepler’s and Tycho’s supernova remnants (SNRs) based on our Chandra HETG observations, and of our far-infrared (FIR) spectroscopic study of unpublished archival SNR data from the Infrared Space Observatory (ISO). We report our measurements of the bulk radial velocity for a sample of clumpy, X-ray-emitting ejecta knots in Kepler’s and Tycho’s SNRs. We measure the Doppler shifts of the He-like Si Kα line center energies in the spectra of these knots based on our Chandra HETGS observations to estimate their radial velocities. We also measure proper motions for our sample based on archival Chandra ACIS data. In Kepler’s SNR, our measured radial velocities and proper motions indicate that the overall X-ray ejecta velocity distribution may be highly asymmetric. It is remarkable that a few ejecta knots are almost freely-expanding at ~ 10,000 km s-1. In Tycho’s SNR, while the spatial velocity distribution of X-ray ejecta knots indicate a generally spherical expansion (with velocities up to ~ 6,000 km s-1 ), we find an apparent asymmetry in the observed Doppler shifts of ejecta knots between the northern and southern shells (more blue-shifts in the north and more red-shifts in the south). We estimate the 3-D location of the reverse shock in Tycho’s SNR based on our velocity measurements. We confirm the relatively high radial velocity (~ -2,000 km s-1 ) of the southeastern protrusion with an uncertainty nearly 10 times smaller than previously possible with Chandra ACIS measurements. We present FIR spectroscopy of 20 SNRs based on archival ISO Long Wavelength Spectrometer (LWS) data. In G21.5–0.9, G29.7–0.3, the Crab Nebula, and G320.4–1.2, we find evidence for broad [O I], [O III], [N II], and [C II] lines with velocity dispersions up to a few 103 km s-1, indicating that they are associated with high-velocity SN ejecta. Our detection of Doppler-broadened atomic emission lines and a bright FIR continuum hints at the presence of newly formed dust in SN ejecta. For G320.4–1.2, we estimate an ejecta dust mass of 0.1–0.2 M. These works were in part supported by NASA Chandra Grants GO6-17060X, AR7-18006X, and 2ADAP Grant 80NSSC20K0449.

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