086551

We have discovered a previously unnoticed X-ray source 3.2 elevkeyOpen circkeyClose away from the Galactic Center. Its XMM-MOS light curve has a periodic variability at 614.28sopenPar approx 3.8 sigma closePar. Its X-ray spectrum is perfectly described by an absorbed 1.8keV blackbody plus Fe-line features. It has an L_keyOpen mathrmkeyOpen XkeyClose keyClose about 1.2times10elevkeyOpen 34keyClose times openParD-10 kpcclosePar elevkeyOpen 2keyClose erg s elevkeyOpen -1keyClose and has no obvious optical counterpartopenParfx-fo > 1600closePar. We argue it is most likely a neutron-star ultra-compact X-ray binary with the shortest orbital period so far. We propose an XMM-PN observation to constrain its nature bydoublePoint 1closePar verifying the 614s signal and looking for a possible rotational period comma 2closeParchecking its new spectral shape and whether other spectral components exist with more X-ray photons.

我们发现了一个此前未被注意到的X射线源，位于距离银心3.2弧分处。其XMM-MOS光变曲线在614.28秒处存在周期性变化（≈3.8σ）。其X射线光谱可通过吸收的1.8keV黑体谱加铁线特征完美描述。其X射线光度L_X约为1.2×10³⁴ ×（D/10 kpc）² erg·s⁻¹，且无明显光学对应体（fx/fo >1600）。我们认为它极有可能是迄今为止轨道周期最短的中子星超紧凑X射线双星。我们提议进行XMM-PN观测以约束其性质：1）验证614秒信号并寻找可能的自转周期；2）利用更多X射线光子检查其新的光谱形状及是否存在其他光谱成分。