A High-Resolution X-Ray Kinematics Study of Kepler's Supernova Remnant
Abstract
We report measurements of the bulk radial velocity from a sample of small, metal-rich ejecta knots in Kepler's supernova remnant (SNR). We measure the Doppler shift of the Si K line center energy in the spectra of these knots from our Chandra High-Energy Transmission Grating Spectrometer (HETGS) observation to estimate their radial velocities. We estimate high radial velocities of up to ~ 9,000 km s-1 for some metal-rich ejecta knots in Kepler's SNR. We also measure proper motions for these ejecta knots based on the archival Advanced CCD Imaging Spectrometer (ACIS) data taken from 2000 to 2014. The fastest moving knots showed proper motions of up to ~ 0.2 arcseconds per year. A few knots with the highest radial velocities also exhibit proper motions which imply an expansion parameter approaching η ~ 1, indicating that they are nearly freely expanding. By assuming that these high velocity ejecta knots are freely expanding, and are located near and beyond the main shell of the SNR, we estimate a distance to Kepler of d ~ 5 to 8.5 kpc. We find that the ejecta knots in our sample have an average space velocity of |v| ~ 5,000 km s-1 (at a distance of 6 kpc). Nearly all the ejecta knots with high radial velocities of |vr| ~ 1,500 km s-1 in our sample show a redshifted spectrum, suggesting a signi cant asymmetry in the ejecta distribution in Kepler's SNR along the line of sight. This work has been supported in part by NASA Chandra Grants GO6-17060X and AR7-18006X.
- Publication:
-
American Astronomical Society Meeting Abstracts #233
- Pub Date:
- January 2019
- Bibcode:
- 2019AAS...23333503M