New publication: “Spatially Resolved RGS Analysis of Kepler’s Supernova Remnant” by Tomoaki Kasuga et al.

The distribution and kinematics of the circumstellar medium (CSM) around a supernova remnant (SNR) tell us useful information about the explosion of its natal supernova (SN). Kepler’s SNR, the remnant of SN 1604, is widely regarded to be of Type Ia origin. Its shock is moving through a dense, asymmetric CSM. The presence of this dense gas suggests that its parent progenitor system consisted of a white dwarf and an asymptotic giant branch (AGB) star. In this paper, we analyze a new and long observation with the reflection grating spectrometers on board the XMM-Newton satellite, spatially resolving the remnant emission in the cross-dispersion direction. We find that the CSM component is blueshifted with velocities in the general range 0–500 km s−1. We also derive information on the central bar structure and find that the northwest half is blueshifted, while the southeast half is redshifted. Our result is consistent with a picture proposed by previous studies, in which a “runaway” AGB star moved to the north-northwest and toward us in the line of sight, although it is acceptable for both single- and core-degenerate scenarios for the progenitor system.

Full article:
Tomoaki Kasuga et al (2021), Spatially Resolved RGS Analysis of Kepler’s Supernova Remnant, The Astrophysical Journal, 915(1), doi: 10.3847/1538-4357/abff4f

New publication: “Shock Heating of Directly Transmitted Ions” by Michael Gedalin

Observations in the heliosphere show that magnetized collisionless shocks are very efficient at ion heating. Ion heating is a nonadiabatic process and the temperature downstream of the shock is not proportional to the upstream temperature. Directly transmitted ions may be responsible for most of the downstream temperature. We determine the gyrophase-dependent distribution of directly transmitted ions just behind the magnetic jump, the gyrotropic distribution farther behind the shock, and establish the relation with the magnetic compression and the maximum overshoot magnetic field. These relations may be used as proxies for estimating the shock Mach number when reliable measurements of density are not available.

Dependence of the magnetic compression at the overshoot on the Mach number MA for various cross-shock potentials.

Full article:
Michael Gedalin (2021), Shock Heating of Directly Transmitted Ions, The Astrophysical Journal, 912(2), doi: 10.3847/1538-4357/abf1e2

License: CC BY 4.0