突破亮度壁垒：JWST/NIRCam DHS光谱用于高精度时序观测
Breaking the brightness barrier: JWST/NIRCam DHS spectroscopy for high-precision time-series observations
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中文总结 AI 辅助
该研究开发了JWST/NIRCam结合DHS与多条纹读出的新型光谱时序模式，突破亮度限制，通过WASP-18b凌星观测验证其用于高精度时序观测的可行性，将扩展至其他JWST光谱模式。
中文摘要 AI 辅助
许多最具科学吸引力的系外行星围绕明亮的近距恒星运行，这些恒星超出了现有JWST光谱观测模式的亮度限制。为解决这一局限，研究人员结合弥散哈特曼传感器（DHS）与新型星上多条纹探测器读出功能，开发了一种新的近红外相机（NIRCam）短波光栅时序模式。DHS通过多个光瞳子孔径色散入射光，降低入射通量，提供约1.0至2.3微米的无狭缝光谱；多条纹读出模式仅读取包含DHS光谱的探测器区域，将标准RAPID读出模式下的探测器帧时间从10.74秒缩短至1.36秒，使用更小的子条纹尺寸时可进一步缩短，从而扩大可观测亮度范围（根据天体光谱类型，K波段约2.5至5.7星等，此前在1.5微米处的限制为K≈5.7星等）。结合同步长波光栅观测，新模式可为K≈2.5星等的明亮目标提供约1.0至5.0微米的光谱连续覆盖。本文展示了该新观测模式在轨调试的首批结果，最终阶段是对系外行星WASP-18b的完整凌星观测，证明了将NIRCam DHS用于高精度时序观测的可行性。本次调试是多条纹探测器读出功能在JWST上的首次部署，除NIRCam DHS外，该新功能还将扩展至其他光谱模式，包括NIRISS SOSS和NIRSpec PRISM。明亮近距恒星是系外行星大气表征的最高优先级目标，因此多条纹功能是最大化JWST科学回报的重要新能力。
英文摘要
Many of the most scientifically compelling exoplanets orbit bright nearby stars that exceed the brightness limits of existing JWST spectroscopic observing modes. To address this limitation, a new NIRCam Short Wavelength Grism Time-Series mode has been developed by combining the Dispersed Hartmann Sensor (DHS) with a new on-board multistripe detector readout capability. The DHS disperses the incoming light through multiple pupil sub-apertures, reducing the incident flux and providing slitless spectroscopy between approximately 1.0 and 2.3 um. The multistripe readout mode further increases the accessible brightness range (K ~ 2.5 - 5.7 mag, depending on the spectral type of the object), with the previous limit being K ~ 5.7 mag at 1.5 um, by reading only the detector regions containing the DHS spectra, reducing the detector frame time with the standard RAPID readout mode from 10.74 s to 1.36 s over even less when using smaller substripe sizes. Together with the simultaneous long-wavelength grism observations, the new mode provides spectroscopic continuous coverage from approximately 1.0 to 5.0 um for targets as bright as K ~ 2.5 mag. We present the first results of on-orbit commissioning of this new observing mode with the final stage consisting of observations of a full transit of the exoplanet WASP-18b, which allowed us to demonstrate the feasibility of using NIRCam DHS for high-precision time-series observations. The commissioning presented in this paper marks the first deployment of the multistripe detector readout on JWST. Beyond NIRCam DHS, this new capability will be extended to other spectroscopic modes, including NIRISS SOSS and NIRSpec PRISM. Bright nearby stars host many of the highest-priority targets for exoplanet atmospheric characterization, making multistripe an important new capability for maximizing the scientific return of JWST.
