2022A&A...663A.122C


Query : 2022A&A...663A.122C

2022A&A...663A.122C - Astronomy and Astrophysics, volume 663A, 122-122 (2022/7-1)

Irradiation-driven escape of primordial planetary atmospheres. II. Evaporation efficiency of sub-Neptunes through hot Jupiters.

CALDIROLI A., HAARDT F., GALLO E., SPINELLI R., MALSKY I. and RAUSCHER E.

Abstract (from CDS):

Making use of the publicly available 1D photoionization hydrodynamics code ATES we set out to investigate the combined effects of specific planetary gravitational potential energy (php ∼ GMp/Rp) and stellar X-ray and extreme ultraviolet (XUV) irradiation (FXUV) on the evaporation efficiency (η) of moderately-to-highly irradiated gaseous planets, from sub-Neptunes through hot Jupiters. We show that the (known) existence of a threshold potential above which energy-limited thermal escape (i.e., η ≃ 1) is unattainable can be inferred analytically, by means of a balance between the ion binding energy and the volume-averaged mean excess energy. For log php ≳ log phpthr ≃ [12.9 - 13.2] (in cgs units), most of the energy absorption occurs within a region where the average kinetic energy acquired by the ions through photo-electron collisions is insufficient for escape. This causes the evaporation efficiency to plummet with increasing php, by up to 4 orders of magnitude below the energy-limited value. Whether or not planets with php ≤ phpthr exhibit energy-limited outflows is primarily regulated by the stellar irradiation level. Specifically, for low-gravity planets, above FXUVthr ≃ 104–5 erg cm–2 s–1, Lyα losses overtake adiabatic and advective cooling and the evaporation efficiency of low-gravity planets drops below the energy-limited approximation, albeit remaining largely independent of php. Further, we show that whereas η increases as FXUV increases for planets above phpthr, the opposite is true for low-gravity planets (i.e., for sub-Neptunes). This behavior can be understood by examining the relative fractional contributions of advective and radiative losses as a function of atmospheric temperature. This novel framework enables a reliable, physically motivated prediction of the expected evaporation efficiency for a given planetary system; an analytical approximation of the best-fitting η is given in the appendix.

Abstract Copyright: © ESO 2022

Journal keyword(s): planets and satellites: atmospheres - planets and satellites: dynamical evolution and stability - planets and satellites: physical evolution

Simbad objects: 16

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Number of rows : 16
N Identifier Otype ICRS (J2000)
RA
ICRS (J2000)
DEC
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
#notes
1 NAME BD-07 436Ab Pl 02 28 37.2277668480 -07 03 38.376446076           ~ 68 1
2 K2-25b Pl 04 13 05.6131374072 +15 14 52.018080576           ~ 78 0
3 NAME LP 424-4b Pl 07 59 05.8395356736 +15 23 29.236065000           ~ 301 1
4 * rho01 Cnc e Pl 08 52 35.8111044043 +28 19 50.954994470           ~ 575 1
5 WASP-43b Pl 10 19 38.0088913464 -09 48 22.605801336           ~ 354 1
6 HD 97658b Pl 11 14 33.1612754184 +25 42 37.390358520           ~ 212 1
7 Ross 905b Pl 11 42 11.0933350978 +26 42 23.650782778           ~ 810 1
8 HD 149026b Pl 16 30 29.6185771608 +38 20 50.308980864           ~ 350 1
9 NAME G 139-21b Pl 17 15 18.9339850845 +04 57 50.066612336           ~ 718 1
10 BD+47 2936b Pl 19 50 50.2472976936 +48 04 51.101390496           ~ 416 1
11 HD 189733b Pl 20 00 43.7129433648 +22 42 39.073143456           ~ 1432 1
12 WASP-80b Pl 20 12 40.1693365800 -02 08 39.187438476           ~ 120 1
13 BD-05 5432b Pl 21 00 06.1968214728 -05 05 40.034944176           ~ 143 1
14 HD 209458b Pl 22 03 10.7727465312 +18 53 03.549393384           ~ 1856 1
15 BD-02 5958b Pl 23 27 04.8376907739 -01 17 10.582653030           ~ 61 0
16 BD-02 5958d Pl 23 27 04.8376907739 -01 17 10.582653030           ~ 47 0

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