A Model of the Hα and Na Transmission Spectrum of HD 189733b

Huang, Chenliang; Arras, Phil; Christie, Duncan; Li, Zhi-Yun

doi:10.3847/1538-4357/aa9b32

Cited by 80 publications

(109 citation statements)

References 72 publications

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“…Next, we will estimate the hydrogen column density that caused the observed transit signal. Using the analytic equations from Huang et al (2017), the number density in the Hydrogen 2 state (n 2 ) can be estimated using the line center optical depth (τ 0 ) τ 0 = 35 n 2 10 4 cm −3 .…”

Section: Resultsmentioning

confidence: 99%

Detection of Ionized Calcium in the Atmosphere of the Ultra-hot Jupiter KELT-9b

Turner

Mooij

Jayawardhana

et al. 2020

ApJL

107

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With a day-side temperature in excess of 4500K, comparable to a mid-K-type star, KELT-9b is the hottest planet known. Its extreme temperature makes KELT-9b a particularly interesting test bed for investigating the nature and diversity of gas giant planets. We observed the transit of KELT-9b at high spectral resolution (R∼94,600) with the CARMENES instrument on the Calar Alto 3.5-m telescope. Using these data, we detect for the first time ionized calcium (Caii triplet) absorption in the atmosphere of KELT-9b; this is the second time that Caii has been observed in a hot Jupiter. Our observations also reveal prominent Hα absorption, confirming the presence of an extended hydrogen envelope around KELT-9b. We compare our detections with an atmospheric model and find that all four lines form between atmospheric temperatures of 6100 K and 8000 K and that the Caii lines form at pressures between 10 and 50 nbar while the Hα line forms at a lower pressure (∼6 nbar), higher up in the atmosphere. The altitude that the core of Hα line forms is found to be ∼1.4 R p , well within the planetary Roche lobe (∼1.9 R p ). Therefore, rather than probing the escaping upper atmosphere directly, the Hα line and the other observed Balmer and metal lines serve as atmospheric thermometers enabling us to probe the planet's temperature profile, thus energy budget.

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Section: Resultsmentioning

confidence: 99%

Detection of Ionized Calcium in the Atmosphere of the Ultra-hot Jupiter KELT-9b

Turner

Mooij

Jayawardhana

et al. 2020

ApJL

107

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“…Given that the difference in the transit radius at the line cores of Na D 1 and D 2 corresponds to ln(2) times of the atmospheric scale height (Huang et al 2017), we can estimate a temperature of ∼4630 K if it is dominated by atomic hydrogen (µ = 1.3). For Hα, we have measured a line FWHM of 15.4 km s −1 , i.e., σ = FWHM/2.355 = 6.5 km s −1 .…”

Section: The Atmosphere Of Wasp-52bmentioning

confidence: 99%

“…For Hα, we have measured a line FWHM of 15.4 km s −1 , i.e., σ = FWHM/2.355 = 6.5 km s −1 . Assuming that Hα originates in a similar layer to the Na doublet and that its line width is set by thermal broadening and the maximum optical depth at line center, based on the equations (3) and (4) In addition to WASP-52b, five other planets have simultaneous detections of Na and Hα, including HD 189733b Jensen et al 2012;Cauley et al 2015Cauley et al , 2016Huang et al 2017), KELT-20b (Casasayas-Barris et al 2019), KELT-9b (Yan & Henning 2018;Cauley et al 2019), WASP-12b (Jensen et al 2018). and WASP-121b (Cabot et al 2020).…”

Section: The Atmosphere Of Wasp-52bmentioning

confidence: 99%

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Detection of Na, K, and Hαabsorption in the atmosphere of WASP-52b using ESPRESSO

Chen

Casasayas-Barris

Πάλλη

et al. 2020

A&A

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WASP-52b is a low density hot Jupiter orbiting a moderately active K2V star. Previous low-resolution studies have revealed a cloudy atmosphere and found atomic Na above the cloud deck. Here we report the detection of excess absorption at the Na doublet, the Hα line, and the K D 1 line. We derived a high-resolution transmission spectrum based on three transits of WASP-52b, observed with the ultra stable, high-resolution spectrograph ESPRESSO at the VLT. We measure a line contrast of 1.09 ± 0.16% for Na D 1 , 1.31 ± 0.13% for Na D 2 , 0.86 ± 0.13% for Hα, and 0.46 ± 0.13% for K D 1 , with a line FWHM range of 11-22 km s −1 . We also find that the velocity shift of these detected lines during the transit is consistent with the planet orbital motion, thus confirming their planetary origin. We do not observe any significant net blueshift or redshift that can be attributed to planetary winds. We use activity indicator lines as control but find no excess absorption. However, we do notice signatures arising from the Center-to-Limb variation (CLV) and the Rossiter-McLaughlin (RM) effect at these control lines. This highlights the importance of the CLV+RM correction in correctly deriving the transmission spectrum, which, if not corrected, could resemble or cancel out planetary absorption in certain cases. WASP-52b is the second non-ultra-hot Jupiter to show excess Hα absorption, after HD 189733b. Future observations targeting non-ultra-hot Jupiters that show Hα could help reveal the relation between stellar activity and the heating processes in the planetary upper atmosphere.

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“…the Doppler shift induced by the thermal motion of atoms or the bulk gas motion. Although these effects will modify aspects of the radiation field such as the penetration of photons in the thermosphere (Huang et al 2017), their rigorous treatment in the framework of our hydrodynamics-NLTE model is currently impractical.…”

Section: Radiative Transfermentioning

confidence: 99%

Rapid Escape of Ultra-hot Exoplanet Atmospheres Driven by Hydrogen Balmer Absorption

Muñoz

Schneider

2019

ApJL

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Atmospheric escape is key to explaining the long-term evolution of planets in our Solar System and beyond, and in the interpretation of atmospheric measurements. Hydrodynamic escape is generally thought to be driven by the flux of extreme ultraviolet photons that the planet receives from its host star. Here, we show that the escape from planets orbiting hot stars proceeds through a different yet complementary process: drawing its energy from the intense near ultraviolet emission of the star that is deposited within an optically thin, high-altitude atmospheric layer of hydrogen excited into the lower state of the Balmer series. The ultra-hot exoplanet KELT-9b likely represents the first known instance of this Balmer-driven escape. In this regime of hydrodynamic escape, the near ultraviolet emission from the star is more important at determining the planet mass loss than the extreme ultraviolet emission, and uncertainties in the latter become less critical. Further, we predict that gas exoplanets around hot stars may experience catastrophic mass loss when they are less massive than 1-2 Jupiter masses and closer-in than KELT-9b, thereby challenging the paradigm that all large exoplanets are stable to atmospheric escape. We argue that extreme escape will affect the demographics of close-in exoplanets orbiting hot stars.

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A Model of the Hα and Na Transmission Spectrum of HD 189733b

Cited by 80 publications

References 72 publications

Detection of Ionized Calcium in the Atmosphere of the Ultra-hot Jupiter KELT-9b

Detection of Ionized Calcium in the Atmosphere of the Ultra-hot Jupiter KELT-9b

Detection of Na, K, and Hαabsorption in the atmosphere of WASP-52b using ESPRESSO

Rapid Escape of Ultra-hot Exoplanet Atmospheres Driven by Hydrogen Balmer Absorption

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