AI 中文总结
本文报道BP Tau的超级耀斑被EP的WXT、FXT与TESS同时观测，明确其X射线与光学辐射的特征，证实联合分析EP与TESS数据研究超级耀斑的潜力
AI 中文摘要
恒星耀斑的多波段观测可追踪恒星外层大气不同成分的活动，为研究各成分间的相互作用提供线索。本文报道了BP Tau的一次超级耀斑，该耀斑同时被爱因斯坦探针（EP）卫星上的广角X射线望远镜（WXT）和TESS观测到。我们将X射线流量的增强归因于磁驱动耀斑，而光学光变曲线可能是耀斑与吸积爆发叠加的结果。X射线耀斑在WXT的0.5-4.0 keV能段内平均流量为(1.5⁺⁰·³₋₀·₄)×10⁻¹¹ erg cm⁻² s⁻¹，上升相和衰减相的e折叠时间分别为1.7±1.0 ks和14±5 ks，对应的时间积分耀斑能量为(1.0±0.2)×10³⁶ erg。光学耀斑的上升相e折叠时间为0.33±0.04 ks，但数据无法约束衰减时标；假设衰减相与上升相相等，TESS的~6000-~10000 Å能段内光学耀斑能量为(2.8±0.4)×10³⁴ erg，对应总辐射能量为(1.9±0.3)×10³⁵ erg（假设为11000 K的黑体）。EP上的后续X射线望远镜（FXT）在耀斑后约1.5天触发观测，测得流量为(4.6⁺⁰·²₋₀·₅)×10⁻¹³ erg cm⁻² s⁻¹（0.5-10.0 keV），表明BP Tau已恢复至宁静态。本研究证明了联合分析EP与TESS数据研究超级耀斑的潜力，WXT预计每年可探测约800次超级耀斑，FXT能在约3-5分钟内转向耀斑恒星，两台设备的大视场为研究高能耀斑期间的多波段变异性提供了机会。
英文摘要
Multiwavelength observations of stellar flares trace the activity of different components of the stars' outer atmosphere, providing insight into their interactions. In the present paper, we report a superflare from BP Tau, simultaneously observed with the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) satellite and TESS. While we attribute the X-ray flux increase to a magnetically powered flare, the optical light curve likely results from the superposition of the flare and an accretion burst. The X-ray flare has a mean flux of $(1.5^{+0.3}_{-0.4})\times10^{-11}$ erg cm$^{-2}$ s$^{-1}$ in the WXT energy band (0.5-4.0 keV), with e-folding times of $1.7\pm1.0$ ks and $14\pm5$ ks for the rise and decay phase, respectively. The corresponding time-integrated flare energy is $(1.0\pm 0.2)\times 10^{36}$ erg. The optical flare has an e-folding time of $0.33\pm0.04$ ks for the rise phase, but the data do not constrain the decay timescale. Assuming a decay phase equal to the rise phase, the resulting optical flare energy is $(2.8\pm0.4)\times10^{34}$ erg in the TESS band ($\sim6,000$-$\sim10,000$ Å), corresponding to a bolometric energy of $(1.9\pm0.3)\times10^{35}$ erg (assuming a blackbody at 11000 K). The Follow-up X-ray Telescope (FXT) on EP triggered an observation $\sim1.5$ day after the flare, with a flux of $(4.6^{+0.2}_{-0.5})\times10^{-13}$ erg cm$^{-2}$ s$^{-1}$ (0.5-10.0 keV), indicating that BP Tau had returned to quiescence. This work demonstrates the potential of jointly analyzing EP and TESS data for superflares. WXT is expected to detect $\sim800$ superflares per year, with FXT capable of slewing to the flaring star within $\sim3$-5 minutes. The large field of view of both missions offers us the opportunity to study multiwavelength variability during energetic flares.
Comments12 pages, 10 figures; accepted by A&A
