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Title: The effects of refraction on transit transmission spectroscopy: application to Earth-like exoplanets

We quantify the effects of refraction in transit transmission spectroscopy on spectral absorption features and on temporal variations that could be used to obtain altitude-dependent spectra for planets orbiting stars of different stellar types. We validate our model against altitude-dependent transmission spectra of the Earth from ATMOS and against lunar eclipse spectra from PallĂ© et al. We perform detectability studies to show the potential effects of refraction on hypothetical observations of Earth analogs with the James Webb Space Telescope NIRSPEC. Due to refraction, there will be a maximum tangent pressure level that can be probed during transit for each given planet-star system. We show that because of refraction, for an Earth-analog planet orbiting in the habitable zone of a Sun-like star only the top 0.3 bars of the atmosphere can be probed, leading to a decrease in the signal-to-noise ratio (S/N) of absorption features by 60%, while for an Earth-analog planet orbiting in the habitable zone of an M5V star it is possible to probe almost the entire atmosphere with minimal decreases in S/N. We also show that refraction can result in temporal variations in the transit transmission spectrum which may provide a way to obtain altitude-dependent spectra of exoplanetmore » atmospheres. Additionally, the variations prior to ingress and subsequent to egress provide a way to probe pressures greater than the maximum tangent pressure that can be probed during transit. Therefore, probing the maximum range of atmospheric altitudes, and in particular the near-surface environment of an Earth-analog exoplanet, will require looking at out-of-transit refracted light in addition to the in-transit spectrum.« less
Authors:
;  [1] ;  [2]
  1. Astronomy Department, University of Washington, Box 351580, Seattle, WA 98195 (United States)
  2. NAI Virtual Planetary Laboratory, Seattle, WA (United States)
Publication Date:
OSTI Identifier:
22365195
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal; Journal Volume: 792; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ABSORPTION; ALTITUDE; ECLIPSE; PLANETS; RADIANT HEAT TRANSFER; REFRACTION; SATELLITE ATMOSPHERES; SIGNAL-TO-NOISE RATIO; SPACE; SPECTRA; SPECTROSCOPY; SUN; TELESCOPES; TRANSMISSION; VARIATIONS; VISIBLE RADIATION