We report the discovery of an annular emission of $\sim$3'-9' radius around the center of a transient source, an X-ray burster MAXI J1421-613, in the Suzaku follow-up analysis. The spectrum of the annular emission shows no significant emission-line structure, and is well explained by an absorbed power law model with a photon index of $\sim$4.2. These features exclude the possibility that the annular emission is a shell-like component of a supernova remnant. The spectral shape, the time history, and the X-ray flux of the annular emission agree with the scenario that the emission is due to a dust-scattering echo. The annular emission is made under a rare condition of the dust-scattering echo, where the central X-ray source, MAXI J1421-613, exhibits a short time outburst with three X-ray bursts and immediately re-enters a long quiescent period. The distribution of the hydrogen column density along the annular emission follows that of the CO intensity, which means that MAXI J1421-613 is located behind the CO cloud. We estimate the distance to MAXI J1421-613 to be $\sim$3~kpc assuming that the dust layer responsible for the annular emission is located at the same position as the CO cloud.

中文翻译：

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发现以 MAXI J1421-613 为中心的环形 X 射线发射：粉尘散射 X 射线？

我们在朱雀的后续分析中报告了在瞬态源（X 射线爆破器 MAXI J1421-613）中心周围 $\sim$3'-9' 半径的环形发射的发现。环形发射的光谱没有显示出显着的发射线结构，并且可以用光子指数为 $\sim$4.2 的吸收幂律模型很好地解释。这些特征排除了环形发射是超新星遗迹的壳状成分的可能性。环形发射的光谱形状、时间历程和 X 射线通量与发射是由尘埃散射回波引起的情景一致。环形发射是在灰尘散射回波的罕见条件下进行的，其中中心 X 射线源 MAXI J1421-613，表现出具有三个 X 射线爆发的短时间爆发，并立即重新进入长时间的静止期。沿环形发射的氢柱密度分布遵循 CO 强度分布，这意味着 MAXI J1421-613 位于 CO 云的后面。我们估计到 MAXI J1421-613 的距离为 $\sim$3~kpc 假设负责环形发射的尘埃层位于与 CO 云相同的位置。