Query : 2022A&A...666L...1S

2022A&A...666L...1S - Astronomy and Astrophysics, volume 666, L1-7 (2022/10-1)

Detection of Paschen β absorption in the atmosphere of KELT-9 b A new window into the atmospheres of ultra-hot Jupiters.


Abstract (from CDS):

Hydrogen and helium transmission signals trace the upper atmospheres of hot gas-giant exoplanets, where the incoming stellar extreme ultraviolet and X-ray fluxes are deposited. Further, for the hottest stars, the near-ultraviolet excitation of hydrogen in the Balmer continuum may play a dominant role in controlling the atmospheric temperature and driving photoevaporation. KELT-9 b is the archetypal example of such an environment as it is the hottest gas-giant exoplanet known to date (Teq ∼ 4500 K) and orbits an A0V-type star. Studies of the upper atmosphere and escaping gas of this ultra-hot Jupiter have targeted the absorption in the Balmer series of hydrogen (n1 = 2 → n2 > 2). Unfortunately, the lowermost metastable helium state that causes the triplet absorption at 1083 Å is not sufficiently populated for detection. This is due to the low extreme-ultraviolet and X-ray fluxes from the host star, and to its high near-ultraviolet flux, which depopulates this metastable state. Here, we present evidence of hydrogen absorption in the Paschen series in the transmission spectrum of KELT-9 b observed with the high-resolution spectrograph CARMENES. Specifically, we focus on the strongest line covered by its near-infrared channel, Paβ at 12 821.6 Å (n1 = 3 → n2 = 5). The observed absorption shows a contrast of (0.53 $ ^{+0.12}_{-0.13} $)%, a blueshift of -14.8 $ ^{+3.5}_{-3.2} $ km s–1, and a full width at half maximum of 31.9$ ^{+11.8}_{-8.3} $ km s–1. The observed blueshift in the absorption feature could be explained by day-to-night circulation within the gravitationally bound atmosphere or, alternatively, by Paβ absorption originating in a tail of escaping gas moving toward the observer as a result of extreme atmospheric evaporation. This detection opens a new window for investigating the atmospheres of ultra-hot Jupiters, providing additional constraints of their temperature structure, mass-loss rates, and dynamics for future modeling of their scorching atmospheres.

Abstract Copyright: © A. Sánchez-López et al. 2022

Journal keyword(s): planets and satellites: atmospheres - planets and satellites: gaseous planets - planets and satellites: individual: KELT-9 b

Simbad objects: 2

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Number of rows : 2
N Identifier Otype ICRS (J2000)
ICRS (J2000)
Mag U Mag B Mag V Mag R Mag I Sp type #ref
1850 - 2024
1 HD 195689b Pl 20 31 26.3534153736 +39 56 19.773037500           ~ 279 0
2 HD 195689 SB* 20 31 26.3534153736 +39 56 19.773037500   7.59 7.56     A0 121 0

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