Chandra Observations of A Galactic Supernova Remnant Vela Jr.: A New Sample of Thin Filaments Emitting Synchrotron X-Rays

A galactic supernova remnant (SNR) Vela Jr. (RX J0852.0$-$4622, G266.6$-$1.2) shows sharp filamentary structure on the north-western edge of the remnant in the hard X-ray band. The filaments are so smooth and located on the most outer side of the remnant. We measured the averaged scale width of the filaments ($w_u$ and $w_d$) with excellent spatial resolution of {\it Chandra}, which are in the order of the size of the point spread function of {\it Chandra} on the upstream side and 49.5 (36.0–88.8) arcsec on the downstream side, respectively. The spectra of the filaments are very hard and have no line-like structure, and were well reproduced with an absorbed power-law model with $\mathrm{\Gamma }=$2.67 (2.55–2.77), or a {\tt SRCUT} model with ${\nu }_{rolloff}$ = 4.3 (3.4–5.3)$\times {10}^{16}$ Hz under the assumption of $p=0.3$. These results imply that the hard X-rays are synchrotron radiation emitted by accelerated electrons, as mentioned previously. Using a correlation between a function $\mathcal{B}\equiv {\nu }_{rolloff}\mathrm{/}{w}_d^2$ and the SNR age, we estimated the distance and the age of Vela Jr.: the estimated distance and age are 0.33 (0.26–0.50) kpc and 660 (420–1400) years, respectively. These results are consistent with previous reports, implying that $\mathcal{B}$–age relation may be a useful tool to estimate the distance and the age of synchrotron X-ray emitting SNRs.