Typically, neutron stars are discovered by observations at radio, X-ray or gamma-ray wavelengths. Unlike radio pulsar surveys and X-ray observations, optical time-domain surveys can unveil and characterize exciting but less explored non-accreting and/or non-beaming neutron stars in binaries. Here we report the discovery of such a neutron star candidate using the LAMOST spectroscopic survey. The candidate, designated LAMOST J112306.9 + 400736, is in a single-lined spectroscopic binary containing an optically visible M star. The star’s large radial velocity variation and ellipsoidal variations indicate a relatively massive unseen companion. Utilizing follow-up spectroscopy from the Palomar 200 in. telescope and high-precision photometry from the Transiting Exoplanet Survey Satellite, we measure a companion mass of \(1.2{4}_{-0.03}^{+0.03}\,{M}_{\odot }\). Main-sequence stars with this mass are ruled out, leaving a neutron star or a massive white dwarf. Although a massive white dwarf cannot be excluded, the lack of UV excess radiation from the companion supports the neutron star hypothesis. Deep radio observations with the Five-hundred-meter Aperture Spherical radio Telescope (FAST) yielded no detections of either pulsed or persistent emission. J112306.9 + 400736 is not detected in numerous X-ray and gamma-ray surveys, suggesting that the neutron star candidate is not currently accreting and pulsing. Our work exemplifies the capability of discovering compact objects in non-accreting close binaries by synergizing optical time-domain spectroscopy and high-cadence photometry.

通常，中子星是通过对射电、X 射线或伽马射线波长的观测发现的。与射电脉冲星勘测和 X 射线观测不同，光学时域勘测可以揭示和表征双星中令人兴奋但探索较少的非吸积和/或非辐射中子星。在这里，我们报告了使用 LMOST 光谱调查发现了这样一个中子星候选者。这颗候选星被命名为LAMOST J112306.9 + 400736，位于一个包含光学可见M星的单线光谱双星中。这颗恒星巨大的径向速度变化和椭球变化表明一个相对巨大的看不见的伴星。利用 Palomar 200 英寸望远镜的后续光谱和凌日系外行星测量卫星的高精度光度测量，我们测量了伴星质量\(1.2{4}_{-0.03}^{+0.03}\,{M}_{\odot }\)。排除了具有这种质量的主序星，剩下一颗中子星或一颗巨大的白矮星。虽然不能排除一颗巨大的白矮星，但伴星没有多余的紫外线辐射支持中子星假说。使用 500 米口径球面射电望远镜 (FAST) 进行的深度射电观测没有检测到脉冲或持续发射。J112306.9 + 400736 在许多 X 射线和伽马射线调查中都没有被发现，这表明候选中子星目前没有吸积和脉动。我们的工作体现了通过协同光学时域光谱学和高节奏光度法在非吸积的近距离双星中发现致密物体的能力。