JWST COMPASS: NIRSpec/G395H Transmission Observations of the Super-Earth TOI-776 b

We present two transit observations of the ∼520 K, 1.85 R⊕, 4.0 M⊕ super-Earth TOI-776 b with JWST NIRSpec/G395H, resulting in a 2.8–5.2 μm transmission spectrum. Producing reductions using the ExoTiC-JEDI and Eureka! pipelines, we obtain a median transit depth precision of 34 ppm for both visits and both reductions in spectroscopic channels 30 pixels wide (∼0.02 μm). We find that our independent reductions produce consistent transmission spectra; however, each visit shows differing overall structure. For both reductions, a flat line is preferred for Visit 1 while a flat line with an offset between the NRS1 and NRS2 detectors is preferred for Visit 2; however, we are able to correct for this offset during our modeling analysis following methods outlined in previous works. Using PICASO forward models, we can rule out metallicities up to at least 100× solar with an opaque pressure of 10−3 bars to ≥3σ in all cases; however, the exact lower limit varies between the visits, with Visit 1 ruling out ≲100× solar while the lower limits for Visit 2 extend beyond ∼350× solar. Our results add to the growing list of super-Earth atmospheric constraints by JWST, which provide critical insight into the diversity and challenges of characterizing terrestrial planets.