AI 中文总结
本研究针对超致密双简并白矮双星eRASSU J060839.5−704014，结合多台X射线望远镜观测数据开展计时与光谱分析，测得其轨道衰减速率快于同类典型系统，证实其为大质量直接撞击型超致密双星，是未来低频引力波研究的重要验证源。
AI 中文摘要
我们利用NICER（中子星内部成分探测器）和Einstein Probe（EP，爱因斯坦探针）的观测数据，结合存档的XMM-Newton数据，对新近发现的超致密双简并（DD）白矮双星eRASSU J060839.5$-$704014开展了计时与光谱分析。通过对长期XMM-Newton、NICER和EP观测数据进行相位连接，我们得到了连贯的二次计时解，测得轨道周期为374.15013(2)秒，轨道衰减率为$\dot{P}= -4.7\\
英文摘要
We present timing and spectral analysis of the recently identified ultracompact double-degenerate (DD) white dwarf binary eRASSU J060839.5$-$704014 using observations from NICER and Einstein Probe (EP), together with archival XMM-Newton data. By phase-connecting the long-term XMM-Newton, NICER, and EP observations, we obtain a coherent quadratic timing solution, yielding an orbital period of 374.15013 (2) s and an orbital decay rate of $\dot{P}= -4.7\,(1) \times 10^{-11} \mathrm{~s~s^{-1}}$. This orbital decay exceeds that measured in the prototypical DD binaries HM Cnc and V407 Vul. Assuming that the observed orbital evolution is primarily driven by gravitational-wave (GW) angular momentum loss, the inferred chirp mass is $\sim0.43\, M_{\odot}$, placing the source among the most massive known systems of this class. The phase-averaged spectra of NICER and EP-Follow-up X-ray Telescope (FXT) are described by a soft thermal component with temperatures of ~126 and ~144 eV, respectively, confirming the supersoft nature of the source. Phase-resolved spectroscopy reveals a clear decrease in temperature across the bright phase in both instruments, indicating a structured emission region with significant temperature gradients. These results establish eRASSU J060839.5$-$704014 as one of the most rapidly evolving ultracompact DD binaries presently known, belonging to the rare class of direct-impact ultracompact binaries, and a promising verification source for future low-frequency GW studies.
CommentsPublished in ApJ Letters
Journal refThe Astrophysical Journal Letters, 1007:L7, 2026 August 10
