GRS 1915+105 X射线遮蔽态中的不同喷流特性
Distinct Jet Properties in the X-Ray-Obscured State of GRS 1915+105
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中文总结 AI 辅助
研究GRS 1915+105 X射线遮蔽态的喷流，发现其喷流形态、速度与未遮蔽态不同，为X射线双星喷流在不同态下传播特性有差异的范式提供了支持。
中文摘要 AI 辅助
GRS 1915+105自2019年从长期未遮蔽态转变后，一直处于X射线遮蔽态。我们报告了2025年用RATAN-600射电望远镜在2.3-11.2 GHz探测到强射电耀斑期间，用东亚甚长基线干涉测量网络（East Asia VLBI Network）对GRS 1915+105开展的6.7 GHz观测。我们的图像揭示了两种截然不同的喷流形态：第一个观测epoch对应从光学厚谱演化到光学薄谱的耀斑，呈现出明亮的射电核，伴随延展的喷流结构；相比之下，第二个epoch观测到另一个耀斑峰值附近，该耀斑在低频段显示光学薄辐射，其核心是两个明亮、对称、分离良好的喷流团块，未探测到可检测的射电核。如果这些喷流表现出2019年前常见的视超光速运动，在五小时观测中应能观测到可测量的角位移，但未检测到显著的喷流运动。结合我们推导的喷流速度βΓ≲0.40，这些结果表明当前遮蔽态下的喷流比早期未遮蔽态观测到的相对论喷流（βΓ≳1）更慢。加上近期报道的喷流方向大幅变化，我们在GRS 1915+105中的发现为新兴范式提供了有力支持：X射线双星在遮蔽态和未遮蔽态下产生的喷流可能表现出不同的传播特性。
英文摘要
GRS 1915+105 has remained in an X-ray-obscured state since its transition from a long-lasting unobscured state in 2019. We report on 6.7-GHz East Asia VLBI Network observations of GRS 1915+105 obtained during strong radio flares detected at 2.3--11.2 GHz with the RATAN-600 radio telescope in 2025. Our images reveal two contrasting jet morphologies. The first epoch, associated with a flare evolving from an optically thick to an optically thin spectrum, shows a bright radio core accompanied by an extended jet structure. By contrast, the second epoch, observed near the peak of another flare displaying optically thin emission at lower frequencies, is dominated by two bright, symmetric, well-separated jet blobs and shows no detectable radio core. If these jets exhibited the apparent superluminal motions commonly observed prior to 2019, measurable angular shifts would be expected over the five-hour observations. However, no significant jet motion is detected. Combined with our derived jet speed of $βΓ\lesssim 0.40$, these results suggest that the jets launched during the current obscured state are slower than the relativistic jets ($βΓ\gtrsim 1$) observed earlier during the unobscured state. Together with the recently reported large variations in jet orientation, our findings in GRS 1915+105 provide robust support for the emerging paradigm that X-ray binary jets launched in obscured and unobscured states likely exhibit distinct propagation properties.
