AI 中文总结
该研究验证了JWST/MIRI的中红外狭缝光谱模式可用于高精度时间序列天文学，其背景比无狭缝模式低约38倍，能提升暗目标观测灵敏度，将于2028年第7周期投入使用。
AI 中文摘要
詹姆斯·韦伯空间望远镜（JWST）上的中红外仪器（MIRI）提供5-12微米波段的低分辨率光谱（LRS），分辨率R约为100。迄今为止，所有MIRI LRS时间序列观测（TSO）均采用无狭缝模式开展，因为此前无法保证在4.7''×0.51''的狭缝内实现长时间指向稳定性，抖动可能导致TSO质量下降。调试活动确认望远镜抖动小于1毫角秒（mas），比初始要求小4倍，因此有必要评估MIRI LRS狭缝作为高精度时间域科学TSO模式的适用性，这是第3周期项目（PID 6219，首席研究员：A. Dyrek）的目标。我们对系外行星HAT-P-12b的一次凌星进行了约10小时的观测，并将结果与同一目标的存档无狭缝观测（PID 1281，首席研究员：P.-O. Lagage）进行对比。对狭缝和无狭缝两种构型的凌星光谱进行的两次独立数据处理结果在1σ范围内一致，验证了新模式的可行性。对狭缝和无狭缝观测的联合拟合确认了7.5微米附近存在光谱特征。利用测得的JWST指向变化，我们估计10微米处的狭缝损失变化小于40 ppm。无狭缝模式的缺点是背景更高，而狭缝模式的背景平均比无狭缝模式低约38倍，可提升对暗目标（J星等约13-15）的灵敏度。我们还在狭缝数据集的长波长处识别出独有的时间相关噪声，需进一步研究。这种将于第7周期（2028年）支持的TSO狭缝模式新能力，为JWST/MIRI开展暗目标高精度时间序列天文学开辟了新途径。
英文摘要
The Mid-Infrared Instrument (MIRI) on board the James Webb Space Telescope (JWST) provides Low Resolution Spectroscopy (LRS) over 5-12 um at a resolving power of R ~ 100. To date, all MIRI LRS time-series observations (TSOs) have been carried out in slitless mode, since long-duration pointing stability within the narrow 4.7'' x 0.51'' slit could not previously be guaranteed, leading to the possibility of degraded TSOs due to jitter. Commissioning activities established the telescope jitter to be less than 1 milliarcsecond (mas), four times less than the initial requirement. It was, therefore, worth assessing the suitability of the MIRI LRS slit as a TSO mode for precision time-domain science; this is the aim of the Cycle 3 program (PID 6219, PI: A. Dyrek). We observed a transit of the exoplanet HAT-P-12b over ~10 hours and compared the results to archival slitless observations of the same target (PID 1281, PI: P.-O. Lagage). Two independent data reductions of the transit spectra of both slit and slitless configurations are consistent within 1 sigma, validating the feasibility of the new mode. A joint fit of the slit and slitless observations confirms the presence of a spectral feature near 7.5 um. Using measured JWST pointing variations, we estimated slit-loss variations to be smaller than 40 ppm at 10 um. The drawback of the slitless mode is a higher background. Compellingly, the slit background is ~ 38 times lower on average than in slitless mode, improving sensitivity for faint targets (Jmag ~ 13-15). We also identified time-correlated noise unique to the slit dataset at long wavelengths, which requires further investigation. This new capability of TSOs in slit mode, which will be supported in Cycle 7 (in 2028), opens a new avenue for precision time-series astronomy for faint targets with JWST/MIRI.
Journal refProceedings Volume 14145, 2026
