2020ApJ...895L..47O


C.D.S. - SIMBAD4 rel 1.7 - 2021.05.17CEST02:02:02

2020ApJ...895L..47O - Astrophys. J., 895, L47-L47 (2020/June-1)

Super-Rayleigh slopes in transmission spectra of exoplanets generated by photochemical haze.

OHNO K. and KAWASHIMA Y.

Abstract (from CDS):

Spectral slopes in optical transmission spectra of exoplanetary atmospheres encapsulate information on the properties of exotic clouds. The slope is usually attributed to the Rayleigh scattering caused by tiny aerosol particles, whereas recent retrieval studies have suggested that the slopes are often steeper than the canonical Rayleigh slopes. Here, we propose that photochemical haze formed in vigorously mixing atmospheres can explain such super-Rayleigh slopes. We first analytically show that the spectral slope can be steepened by the vertical opacity gradient in which atmospheric opacity increases with altitude. Using a microphysical model, we demonstrate that such an opacity gradient can be naturally generated by photochemical haze, especially when the eddy mixing is substantially efficient. The transmission spectra of hazy atmospheres can be demarcated into four typical regimes in terms of the haze mass flux and eddy diffusion coefficient. We find that the transmission spectrum can have a spectral slope 2-4 times steeper than the Rayleigh slope if the eddy diffusion coefficient is sufficiently high and the haze mass flux falls into a moderate value. Based on the eddy diffusion coefficient suggested by a recent study of atmospheric circulations, we suggest that photochemical haze preferentially generates super-Rayleigh slopes at planets with equilibrium temperatures of 1000-1500 K, which might be consistent with results of recent retrieval studies. Our results would help interpret the observations of spectral slopes from the perspective of haze formation.

Abstract Copyright: © 2020. The American Astronomical Society. All rights reserved.

Journal keyword(s): Exoplanet atmospheres - Hot Jupiters - Optical observation - Transmission spectroscopy

Simbad objects: 14

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Number of rows : 14

N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2021
#notes
1 NAME LP 424-4b Pl 07 59 05.8395618539 +15 23 29.240025256           ~ 190 1
2 WASP-19b Pl 09 53 40.0764883458 -45 39 33.055979403           ~ 283 1
3 BD-03 2978b Pl 10 42 14.0835894932 -03 50 06.259823354           ~ 39 0
4 WASP-31b Pl 11 17 45.3578468391 -19 03 17.216528280           ~ 97 1
5 HAT-P-12b Pl 13 57 33.4668502171 +43 29 36.602501754           ~ 137 1
6 WASP-39b Pl 14 29 18.4151765921 -03 26 40.203046112           ~ 107 1
7 CD-27 10695b Pl 15 59 50.9489706053 -28 03 42.309432433           ~ 207 1
8 NAME G 139-21b Pl 17 15 18.9337265994 +04 57 50.064695682           ~ 574 1
9 HATS-8b Pl 19 39 46.0127075591 -25 44 54.009190372           ~ 26 0
10 BD+47 2936b Pl 19 50 50.2474562793 +48 04 51.097364378           ~ 323 1
11 HD 189733b Pl 20 00 43.7130382888 +22 42 39.071811263           ~ 1168 1
12 HD 209458b Pl 22 03 10.7729598762 +18 53 03.548248479           ~ 1568 1
13 NAME BD+37 4734Bb Pl 22 57 46.8443014981 +38 40 30.355384717           ~ 209 1
14 WASP-6b Pl 23 12 37.7368657624 -22 40 26.277489164           ~ 106 1

    Equat.    Gal    SGal    Ecl

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2021.05.17-02:02:02

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