首次在690GHz实现甚长基线干涉测量条纹检测
First Very Long Baseline Interferometry Fringe Detection at 690GHz
AI总结：
本文报告了在690 GHz大气窗口首次成功进行的VLBI实验，利用ALMA、APEX和JCMT望远镜，在ALMA-APEX基线上检测到信噪比约12的条纹，验证了近太赫兹VLBI运行的关键技术，为常规观测奠定基础。
AI中文摘要：
我们报告了在690 GHz大气窗口进行的首次甚长基线干涉测量（VLBI）实验。2024年11月21日，利用阿塔卡马大型毫米/亚毫米波阵列（ALMA）新开发的Band 9相位校正能力，与阿塔卡马探路者实验（APEX）和詹姆斯·克拉克·麦克斯韦望远镜（JCMT）联合开展了观测。在对类星体J0423-0120的一次扫描中，在ALMA-APEX基线上检测到了条纹，信噪比约为12，在数十秒量级的解算区间内实现了有效的条纹恢复，这是迄今报道的频率最高的地面VLBI条纹检测。尽管天气条件极佳，但在ALMA-JCMT基线上未发现条纹，这与灵敏度预测一致，并支持了基线性能模型。ALMA相位系统在Band 9下保持了约1-2分钟的稳定相位，随后逐渐退化，表明在该观测条件下存在局限性。我们的分析表明，在极佳天气条件下，尽管这些频率下大气相位波动剧烈，690 GHz VLBI仍能在短解算区间内支持条纹恢复。这项工作验证了近太赫兹VLBI运行的关键要素，并为在690 GHz大气窗口进行常规观测奠定了技术基础。
英文摘要：
We report the first very long baseline interferometry (VLBI) experiment conducted in the 690 GHz atmospheric window. On 2024 November 21, observations with the Atacama Large Millimeter/submillimeter Array, the Atacama Pathfinder EXperiment (APEX), and the James Clerk Maxwell Telescope (JCMT) were carried out using ALMA's newly developed Band 9 phasing capability. Fringes were detected on the ALMA-APEX baseline during a scan of the quasar J0423-0120, with a signal-to-noise ratio of ~12 and useful fringe recovery over solution intervals of order tens of seconds, representing the highest-frequency ground-based VLBI fringe detection reported to date. No fringes were found on the ALMA-JCMT baseline, despite excellent weather conditions, consistent with sensitivity predictions and supporting baseline performance models. The ALMA Phasing System maintained stable phasing at Band 9 for ~1-2 minutes before gradually degrading, indicating limitations under these observing conditions. Our analysis shows that, under excellent weather conditions, 690 GHz VLBI can still support fringe recovery over short solution intervals, despite rapid atmospheric phase fluctuations at these frequencies. This work validated key elements of near-terahertz VLBI operation and establishes a technical foundation for routine observations in the 690 GHz atmospheric window.
