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Proceedings Paper

Observing exoplanets with the JWST NIRCam grisms
Author(s): Thomas Greene; Charles Beichman; Daniel Eisenstein; Scott Horner; Douglas Kelly; Yalan Mao; Michael Meyer; Marcia Rieke; Fang Shi
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Paper Abstract

The near-infrared camera (NIRCam) on the James Webb Space Telescope (JWST) will incorporate 2 identical grisms in each of its 2 long wavelength channels. These transmission gratings have been added to assist with the coarse phasing of the JWST telescope, but they will also be used for slitless wide-field scientific observations over selectable regions of the λ = 2.4 − 5.0 μm wavelength range at spectroscopic resolution R ≡ λ/δλ ≃ 2000. We describe the grism design details and their expected performance in NIRCam. The grisms will provide point-source continuum sensitivity of approximately AB = 23 mag in 10,000 s exposures with S/N = 5 when binned to R = 1000. This is approximately a factor of 3 worse than expected for the JWST NIRSpec instrument, but the NIRCam grisms provide better spatial resolution, better spectrophotometric precision, and complete field coverage. The grisms will be especially useful for high precision spectrophotometric observations of transiting exoplanets. We expect that R = 500 spectra of the primary transits and secondary eclipses of Jupiter-sized exoplanets can be acquired at moderate or high signal-to-noise for stars as faint as M = 10 − 12 mag in 1000 s of integration time, and even bright stars (V = 5 mag) should be observable without saturation. We also discuss briefly how these observations will open up new areas of exoplanet science and suggest other unique scientific applications of the grisms.

Paper Details

Date Published: 19 September 2007
PDF: 10 pages
Proc. SPIE 6693, Techniques and Instrumentation for Detection of Exoplanets III, 66930G (19 September 2007); doi: 10.1117/12.732506
Show Author Affiliations
Thomas Greene, NASA Ames Research Ctr. (United States)
Charles Beichman, California Institute of Technology (United States)
Daniel Eisenstein, The Univ. of Arizona/Steward Observatory (United States)
Scott Horner, Lockheed Martin Advanced Technology Ctr. (United States)
Douglas Kelly, The Univ. of Arizona/Steward Observatory (United States)
Yalan Mao, Lockheed Martin Advanced Technology Ctr. (United States)
Michael Meyer, The Univ. of Arizona/Steward Observatory (United States)
Marcia Rieke, The Univ. of Arizona/Steward Observatory (United States)
Fang Shi, Jet Propulsion Lab. (United States)


Published in SPIE Proceedings Vol. 6693:
Techniques and Instrumentation for Detection of Exoplanets III
Daniel R. Coulter, Editor(s)

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