标题： AR Scorpii 的一个兄弟星：SDSS J230641.47$+$244055.8 以及白矮星脉冲星的观测蓝图 显示英文标题

标题： A Sibling of AR Scorpii: SDSS J230641.47$+$244055.8 and the Observational Blueprint of White Dwarf Pulsars

摘要： 脉动白矮星（WD）系统，称为WD脉冲星，是不吸积的双星系统，其中快速旋转的WD与低质量伴星相互作用，产生可以在整个电磁波谱中观测到的脉冲非热辐射。 目前已知只有两个这样的系统：AR Sco和eRASSU J191213.9$-$441044。 在此我们报告发现第三个WD脉冲星，SDSS J230641.47$+$244055.8。 光学光谱主要由M型矮星伴星的分子带主导，并伴有来自巴尔末系和He I的窄发射线。 长期光学光变曲线在轨道周期（$P_\mathrm{orb} = 3.49$h）上折叠后表现出较大的散射（约10%）。 高时间分辨率测光显示一个短周期信号，我们将其解释为WD主星的自转周期（$P_\mathrm{spin} \simeq 92$s）。 WD自转周期比AR Sco（$\rm \sim 117$s）稍短，AR Sco是WD脉冲星的原型。 时间分辨光谱显示来自被照射伴星的发射和Na I吸收线，这些吸收线大致追踪其质心，由此得到二元质量函数为$f(M) \simeq 0.2 {\rm M_\odot}$。 H$\alpha$发射包括一个低振幅宽成分，类似于AR Sco中看到的能量发射线闪光。 使用光谱模板，我们将伴星分类为最可能是$\rm M4.0\pm 0.5$星，温度为$T_\mathrm{\rm eff} \approx 3300$K。对恒星贡献的建模限制了次级质量（$0.19\,{\rm M_\odot}\lesssim M_2\lesssim 0.28\,{\rm M_\odot}$）、系统距离（$\simeq1.25\,{\rm kpc}$）和倾角（$i \simeq 45-50^\circ$）。 我们讨论了提出的演化情景，并总结了所有三个已知的WD脉冲星的观测特性，为识别和分类这一新兴类别的未来成员建立了基准。 显示英文摘要

摘要： Radio pulsating white dwarf (WD) systems, known as WD pulsars, are non-accreting binary systems where the rapidly spinning WD interacts with a low-mass companion producing pulsed non-thermal emission that can be observed across the entire electromagnetic spectrum. Only two such systems are known: AR Sco and eRASSU J191213.9$-$441044. Here we present the discovery of a third WD pulsar, SDSS J230641.47$+$244055.8. The optical spectrum is dominated by molecular bands from an M-dwarf companion, with additional narrow emission lines from the Balmer series and He I. The long-term optical light-curve folded on its orbital period ($P_\mathrm{orb} = 3.49$ h) exhibits large scatter (roughly 10 per cent). High-cadence photometry reveals a short period signal, which we interpret to be the spin period of the WD primary ($P_\mathrm{spin} \simeq 92$ s). The WD spin period is slightly shorter than that of AR Sco ($\rm \sim 117$ s), the WD pulsar prototype. Time-resolved spectroscopy reveals emission from the irradiated companion and Na I absorption lines approximately tracing its centre of mass, which yields a binary mass function of $f(M) \simeq 0.2 {\rm M_\odot}$. The H$\alpha$ emission includes a low-amplitude broad component, resembling the energetic emission line flashes seen in AR Sco. Using spectral templates, we classify the companion to be most likely a $\rm M4.0\pm 0.5$ star with $T_\mathrm{\rm eff} \approx 3300$ K. Modelling the stellar contribution constrains the secondary mass ($0.19\,{\rm M_\odot}\lesssim M_2\lesssim 0.28\,{\rm M_\odot}$), system distance ($\simeq1.25\,{\rm kpc}$), and inclination ($i \simeq 45-50^\circ$). We discuss the proposed evolutionary scenarios and summarize the observational properties of all three known WD pulsars, establishing a benchmark for identifying and classifying future members of this emerging class.