Spectroscopic Time-series Performance of JWST/NIRSpec from Commissioning Observations
Nikolov, Nikolay; Sing, David K.; Böker, Torsten; Kumari, Nimisha; Valenti, Jeff A.; Rustamkulov, Zafar; Espinoza, Néstor; Úbeda, Leonardo; Kendrew, Sarah; Ferruit, Pierre; Giardino, Giovanna; Manjavacas, Elena; Sabbi, Elena; Albert, Loïc; Greene, Thomas P.; Schlawin, Everett; Beatty, Thomas; Regan, Michael; Karakla, Diane; Alves de Oliveira, Catarina; Proffitt, Charles; Birkmann, Stephan M.; Rawle, Timothy; Keyes, Charles; Pena-Guerrero, Maria
United States, Spain, Canada, Netherlands
Abstract
We report on James Webb Space Telescope (JWST) commissioning observations of the transiting exoplanet HAT-P-14 b, obtained using the Bright Object Time Series (BOTS) mode of the NIRSpec instrument with the G395H/F290LP grating/filter combination (3-5 μm). While the data were used primarily to verify that the NIRSpec BOTS mode is working as expected, and to enable it for general scientific use, they yield a precise transmission spectrum which we find is featureless down to the precision level of the instrument, consistent with expectations given HAT-P-14 b's small scale-height and hence expected atmospheric features. The exquisite quality and stability of the JWST/NIRSpec transit spectrum-almost devoid of any systematic effects-allowed us to obtain median uncertainties of 50-60 ppm in this wavelength range at a resolution of R = 100 in a single exposure, which is in excellent agreement with pre-flight expectations and close to the (or at the) photon-noise limit for a J = 9.094, F-type star like HAT-P-14. These observations showcase the ability of NIRSpec/BOTS to perform cutting-edge transiting exoplanet atmospheric science, setting the stage for observations and discoveries to be made in Cycle 1 and beyond.