Spectroscopic Study of the Vela-Shrapnel

Several shrapnels have been detected in the vicinity of Vela SNR by the ROSATall-sky survey. We present here the spectral properties of shrapnel `A'observed with the ASCA satellite. A prominent Si-K emission line withrelatively weak emission lines from other elements have been detected,revealing that the relative abundance of Si is a few ten-times higher thanthose of other elements. Combining with the ROSAT PSPC results, we obtained theelectron temperature, $kT_{\rm e}$, to be $0.33 \pm 0.01$ keV. The total massof shrapnel `A' is estimated to be $\sim 0.01 M_\odot$. If it is an ejecta of asupernova explosion, the interstellar matter (ISM) would be swept up in theleading edge while the ejecta material would be peeled off in the trailingedge, which should be confirmed by future observations.Comment: 19pages, 5 figures, 1 table; Accepted for Publications of the Astronomical Society of Japa