J/ApJ/795/L14 Refracted light signals to discriminate exoplanets (Misra+, 2014)
Discriminating between cloudy, hazy, and clear sky exoplanets using refraction.
Misra A.K., Meadows V.S.
<Astrophys. J., 795, L14 (2014)>
=2014ApJ...795L..14M 2014ApJ...795L..14M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Models, atmosphere
Keywords: planets and satellites: atmospheres
Abstract:
We propose a method to distinguish between cloudy, hazy, and clear sky
(free of clouds and hazes) exoplanet atmospheres that could be
applicable to upcoming large aperture space- and ground-based
telescopes such as the James Webb Space Telescope (JWST) and the
European Extremely Large Telescope (E-ELT). These facilities will be
powerful tools for characterizing transiting exoplanets, but only
after a considerable amount of telescope time is devoted to a single
planet. A technique that could provide a relatively rapid means of
identifying haze-free targets (which may be more valuable targets for
characterization) could potentially increase the science return for
these telescopes. Our proposed method utilizes broadband observations
of refracted light in the out-of-transit spectrum. Light refracted
through an exoplanet atmosphere can lead to an increase of flux prior
to ingress and subsequent to egress. Because this light is transmitted
at pressures greater than those for typical cloud and haze layers, the
detection of refracted light could indicate a cloud- or haze-free
atmosphere. A detection of refracted light could be accomplished in
<10 hr for Jovian exoplanets with JWST and <5 hr for
super-Earths/mini-Neptunes with E-ELT. We find that this technique is
most effective for planets with equilibrium temperatures between 200
and 500 K, which may include potentially habitable planets. A
detection of refracted light for a potentially habitable planet would
strongly suggest the planet was free of a global cloud or haze layer,
and therefore a promising candidate for follow-up observations.
Description:
We used a suite of planetary atmospheres to calculate the refracted
light signal. We have selected a combination of solar system analogs
as well possible super-Earth and mini-Neptune atmospheres to cover a
wide range of potential planetary atmospheres. We assumed the
H2-dominated atmospheres have a solar H/He ratio (90% H, 10% He) for
simplicity, but the small change in the refractive index for different
H/He ratios should have a negligible effect on our results. For the
super-Earth and mini-Neptune planets, we ran our models on four test
cases to span the most likely bulk atmospheric compositions: 100% N2,
solar composition, 100% H2O, and 100% CO2.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 85 145920 Refracted Light Signals
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See also:
J/ApJ/761/166 : Terrestrial exoplanet atmospheres. I. (Hu+, 2012)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- PType Planet type
17- 20 I4 K Tp Planetary equilibrium temperature
22- 25 I4 K T* Stellar temperature
27- 34 A8 --- AType Atmosphere type
37- 40 F4.2 --- Albedo Planetary albedo
42- 47 F6.2 ppm Flux Flux difference
49- 54 F6.2 h E-ELTint ?=999 E-ELT integration time (2) (1)
56- 60 F5.1 --- E-ELTtrans ?=999 Number of E-ELT transits (2) (1)
62- 66 F5.1 yr E-ELTtot ?=999 Total E-ELT time from first to last
transit (2) (1)
68- 73 F6.2 h JWSTint JWST Integration time (2)
75- 79 F5.1 --- JWSTtrans Number of JWST transits (2)
81- 85 F5.1 yr JWSTtot Total JWST time from first to last
transit (2)
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Note (1): The E-ELT results were calculated assuming 50 spectral resolution
elements could be binned over.
Note (2): Values greater than 999 are listed as '999.00' and should be
considered lower limits.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 17-May-2017