Shout-out to all my collaborators on this paper who made this possible. Especially @benjaminpope.bsky.social for encouraging me to follow these "odd" data quirks
Thread on our new paper on arxiv today! We stumbled across a weird sinusoidal systematic that we think appears in every observation from the NIRISS instrument on JWST. We derive a correction and see how much it impacts exoplanet spectra. (1/N) #astro #exoplanets 🔭🧪
arxiv.org/abs/2606.11983
Shashank Dholakia
We quantify an unusual flux-dependent systematic which is periodic in raw counts in flight data from the James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST/NIRISS), used...
Forgot to mention in this thread! I have posted a barebones script to correct uncal NIRISS data using the sinusoid we infer in our paper. Would be great to try it on any NIRISS data you have lying around and see what the effects are on your data! #astro #exoplanets 🔭
github.com/shashankdhol...
Calibrating the JWST NIRISS analog-to-digital converter periodic integral nonlinearity - shashankdholakia/niriss-cal-inl
github.com
And finally--the transmission spectra before and after the correction (with the difference on the bottom). The most obvious effect of the sinusoidal systematic is to offset Orders 1 and 2 in NIRISS, which we estimate for WASP-39b at 55ppm. It also seemingly randomly disperses points by ~30ppm. (9/N)
