James Webb Space Telescope Feed Post

Arxiv: The JWST Early Release Science Program for Direct Observations of Exoplanetary Systems IV: NIRISS Aperture Masking Interferometry Performance and Lessons Learned Published: 10/17/2023 9:00:07 PM Updated: 10/17/2023 9:00:07 PM

Paper abstract: We present a performance analysis for the aperture masking interferometry(AMI) mode on board the James Webb Space Telescope Near Infrared Imager andSlitless Spectrograph (JWST/NIRISS). Thanks to self-calibrating observables,AMI accesses inner working angles down to and even within the classicaldiffraction limit. The scientific potential of this mode has recently beendemonstrated by the Early Release Science (ERS) 1386 program with a deep searchfor close-in companions in the HIP 65426 exoplanetary system. As part of ERS1386, we use the same dataset to explore the random, static, and calibrationerrors of NIRISS AMI observables. We compare the observed noise properties andachievable contrast to theoretical predictions. We explore possible sources ofcalibration errors, and show that differences in charge migration between theobservations of HIP 65426 and point-spread function calibration stars canaccount for the achieved contrast curves. Lastly, we use self-calibration teststo demonstrate that with adequate calibration, NIRISS AMI can reach contrastlevels of ~9-10 mag. These tests lead us to observation planningrecommendations and strongly motivate future studies aimed at producingsophisticated calibration strategies taking these systematic effects intoaccount. This will unlock the unprecedented capabilities of JWST/NIRISS AMI,with sensitivity to significantly colder, lower mass exoplanets thanground-based setups at orbital separations inaccessible to JWST coronagraphy.