Kepler ’ s supernova remnant ( SNR ) is believed to result from a Type Ia supernova , but be interacting with dense circumstellar material ( CSM ) , which makes its progenitor system a mystery .
Using the Chandra ACIS-S 741 ks effective exposure data and an advanced adaptive binning algorithm , we analyse the spectra from tessellated regions in Kepler ’ s SNR .
For the first time , we map out the detailed spatial distributions of emission measure ( EM ) , electron temperature , ionization parameter , and metal abundances for both the low- and high-temperature plasma components .
The low-temperature plasma diverges into two branches in the temperature v.s. ionization parameter diagram , which appear to be spatially associated with the warm CSM dusts and the Si- and S-rich ejecta , respectively .
We construct the probability distribution functions of abundance ratios of O and Mg to L-shell emitting Fe ( [ O ] / [ Fe ] _ { L } and [ Mg ] / [ Fe ] _ { L } ) , and fit them with double Gaussians .
Thereby , we distinguish the CSM from the ejecta : the CSM is characterized by [ O ] / [ Fe ] _ { L } = 0.77 ^ { +0.30 } _ { -0.23 } and [ Mg ] / [ Fe ] _ { L } = 1.11 ^ { +0.46 } _ { -0.32 } , while the ejecta by [ O ] / [ Fe ] _ { L } = 0.31 ^ { +0.17 } _ { -0.10 } and [ Mg ] / [ Fe ] _ { L } = 0.38 ^ { +0.36 } _ { -0.19 } .
We estimate the total hydrogen mass of the shocked CSM as \sim 1.4 M _ { \odot } and the EM-weighted mean [ Mg ] / [ O ] = 1.14 \pm 0.49 , which can be reproduced with an asymptotic giant branch donor star with initial mass of \sim 4 M _ { \odot } .
The abundance ratios from the shocked ejecta are well compatible with the predicted results from spherical delayed-detonation models for Type Ia supernovae .
We also find that the two “ ears ” of the remnant are dominated by Si- and S-rich ejecta , thus favoring a pre-explosion jets scenario .