AI 中文总结
研究最暗早期X射线探测到的光学潮汐瓦解事件TDE 2025aarm，通过X射线和光学光谱分析，发现其有从低硬到高软再变硬的光谱状态转变，类似黑洞X射线双星，还确认分类及荧光特征，为TDE吸积物理等提供新见解。
AI 中文摘要
我们报告了TDE 2025aarm的X射线和光学光谱特性，它是迄今为止发现的第二近的潮汐瓦解事件（TDE）。该源的距离，加上为期六个月的深度且密集的X射线监测活动，使我们能够探测到接近光学峰值时前所未有的0.2 - 10 keV光度，约为\(\sim7\times10^{39}\)尔格每秒，这使得TDE 2025aarm成为迄今为止最暗的早期X射线探测到的TDE。首次X射线探测后，该源亮度增加了近两个数量级，在光学峰值约四个月后达到峰值光度\(\sim5\times10^{41}\)尔格每秒。通过时间分辨X射线光谱分析，我们发现TDE 2025aarm随着光度增加，从最初硬的、幂律主导的X射线状态演变为更软的、盘主导的状态，之后在后期再次变硬。这种低硬到高软的状态转变通常在黑洞X射线双星（XRB）中观察到，但此前在热TDE中尚未报道。我们表明光谱演化可以通过吸积盘和康普顿化成分的相对贡献变化来描述，定性上类似于在XRB中观察到的盘 - 日冕演化。我们还展示了使用HET/LRS2进行的光学光谱后续观测活动的结果，确认了TDE分类并揭示了NIII鲍恩荧光特征。TDE 2025aarm极其微弱的早期X射线发射进一步支持了这样一种观点，即X射线明亮和未探测到的TDE之间的历史二分法在很大程度上是由与X射线后续观测的深度、节奏和持续时间相关的选择效应驱动的。因此，TDE 2025aarm为TDE的吸积物理以及跨越几个黑洞质量数量级的吸积可能的普遍性提供了新的见解。
英文摘要
We report the X-ray and optical spectroscopic properties of TDE 2025aarm, the second closest tidal disruption event (TDE) discovered to date. The proximity of this source, combined with a deep and intense X-ray monitoring campaign spanning six months, allowed us to probe the source down to an unprecedented 0.2-10 keV luminosity of $\sim7\times10^{39}$ erg s$^{-1}$ close to the optical peak. This renders TDE 2025aarm the faintest early-X-ray-detected TDE to date. After the first X-ray detection, the source brightened by nearly two orders of magnitude, reaching a peak luminosity of $\sim5\times10^{41}$ erg s$^{-1}$ about four months after the optical peak. Through time-resolved X-ray spectral analysis, we find that TDE 2025aarm evolved from an initially hard, power-law-dominated X-ray state into a softer, disk-dominated state as the luminosity increased, before hardening again at later times. Such low-hard-to-high-soft state transitions are commonly observed in black hole X-ray binaries (XRBs) but have not previously been reported in thermal TDEs. We show that the spectral evolution can be described by variations in the relative contributions of an accretion disk and a Comptonizing component, qualitatively resembling the disk--corona evolution observed in XRBs. We also present the results of our optical spectroscopic follow-up campaign with HET/LRS2, confirming the TDE classification and revealing NIII Bowen fluorescence features. The extremely faint early-time X-ray emission of TDE 2025aarm further supports the idea that the historical dichotomy between X-ray-bright and X-ray-undetected TDEs is largely driven by selection effects related to the depth, cadence, and duration of X-ray follow-up observations. TDE 2025aarm therefore provides new insight into both the accretion physics of TDEs and the possible universality of accretion across several orders of magnitude in black hole mass.
Comments12 pages, 6 figures (+ appendices). Submitted to A&A
