paper

Spectroscopic Time-series Performance of JWST/NIRSpec from Commissioning Observations

arXiv:2211.01459 · doi:10.1088/1538-3873/aca3d3

Abstract

We report on 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 (m). 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 \emph{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 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 , 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.

16 pages, 14 figures; part of the PASP Focus Issue "JWST Time-Series Observations: Commissioning Performance". Paper after the first round of referee comments; inputs welcome

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