Dynamics of X-Ray-Emitting Ejecta in the Oxygen-Rich Supernova Remnant Puppis A Revealed by the XMM-Newton RGS

TL;DR

This study uses high-resolution X-ray spectroscopy to analyze ejecta dynamics in the supernova remnant Puppis A, revealing shock velocities, temperature constraints, and ejecta motions consistent with optical observations.

Contribution

First detailed X-ray spectral analysis of Puppis A's ejecta revealing shock velocities and temperature equilibration using XMM-Newton RGS data.

Findings

Ejecta knot blueshifted by ~1480 km/s, matching optical filament velocity.

Oxygen temperature constrained to less than ~30 keV.

Ejecta features show Doppler velocities of ~650 km/s.

Abstract

Using the unprecedented spectral resolution of the reflection grating spectrometer (RGS) onboard XMM-Newton, we reveal dynamics of X-ray--emitting ejecta in the oxygen-rich supernova remnant Puppis A. The RGS spectrum shows prominent K-shell lines, including O VII He_alpha forbidden and resonance, O VIII Ly_alpha, O VIII Ly_beta, and Ne IX He_alpha resonance, from an ejecta knot positionally coincident with an optical oxygen-rich filament (the so-called Omega filament in the northeast of the remnant). We find that the line centroids are blueshifted by 1480+/-140+/-60 km/s (the first and second term errors are measurement and calibration uncertainties, respectively), which is fully consistent with that of the optical Omega filament. Line broadening at 654 eV (corresponding to O VIII Ly_alpha) is obtained to be less than ~0.9 eV, indicating an oxygen temperature of less than ~30 keV. Analysis of XMM-Newton MOS spectra shows an electron temperature of ~0.8 keV and an ionization timescale of ~2e10 cm^-3 s. We show that the oxygen and electron temperatures as well as the ionization timescale can be reconciled if the ejecta knot was heated by a collisionless shock whose velocity is ~600-1200 km/s and was subsequently equilibrated due to Coulomb interactions. The RGS spectrum also shows relatively weak K-shell lines of another ejecta feature located near the northeastern edge of the remnant, from which we measure redward Doppler velocities of 650+/-70+/-60 km/s.