Modeling the Hα and He 10830 Transmission Spectrum of WASP-52b

Yan, Dongsheng; Seon, Kwang‐Il; Guo, J.; Chen, G.; Li, Lifang

doi:10.3847/1538-4357/ac8793

“…This is still an order of magnitude smaller than the prediction from ATES in Figure 4 (  = ḰM 4.7 10 11 g s −1 ) after accounting for the K = 0.43 correction factor. Both Kirk et al (2022) and the subsequent modeling effort by Yan et al (2022) found similar inferred outflow rates that are not very sensitive to the assumed composition. Additionally Kirk et al (2022) found that the outflow is not strongly confined by stellar winds, as they do not observe a Doppler-shifted line profile or a tail.…”

Section: Discussionmentioning

confidence: 74%

“…Lastly, observations of the Hα absorption signal from both planets could also provide constraints on the outflow composition (Czesla et al 2022). Hα absorption has already been detected and used to constrain the composition for WASP-52b (Chen et al 2020;Yan et al 2022); similar constraints should also be obtained for WASP-80b.…”

Section: Discussionmentioning

confidence: 90%

The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation

Vissapragada¹,

Knutson²,

et al. 2022

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Transit surveys indicate that there is a deficit of Neptune-sized planets on close-in orbits. If this “Neptune desert” is entirely cleared out by atmospheric mass loss, then planets at its upper edge should only be marginally stable against photoevaporation, exhibiting strong outflow signatures in tracers like the metastable helium triplet. We test this hypothesis by carrying out a 12-night photometric survey of the metastable helium feature with Palomar/WIRC, targeting seven gas-giant planets orbiting K-type host stars. Eight nights of data are analyzed here for the first time along with reanalyses of four previously published data sets. We strongly detect helium absorption signals for WASP-69b, HAT-P-18b, and HAT-P-26b; tentatively detect signals for WASP-52b and NGTS-5b; and do not detect signals for WASP-177b and WASP-80b. We interpret these measured excess absorption signals using grids of Parker wind models to derive mass-loss rates, which are in good agreement with predictions from the hydrodynamical outflow code ATES for all planets except WASP-52b and WASP-80b, where our data suggest that the outflows are much smaller than predicted. Excluding these two planets, the outflows for the rest of the sample are consistent with a mean energy-limited outflow efficiency of ε = 0.41 − 0.13 + 0.16 . Even when we make the relatively conservative assumption that gas-giant planets experience energy-limited outflows at this efficiency for their entire lives, photoevaporation would still be too inefficient to carve the upper boundary of the Neptune desert. We conclude that this feature of the exoplanet population is a pristine tracer of giant planet formation and migration mechanisms.

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“…The strong Hα absorption feature observed on WASP-121b calls for careful consideration of the distribution of excitedstate H. As has been shown in previous works (Huang et al 2017;García Muñoz & Schneider 2019;Miroshnichenko et al 2021;Yan et al 2021Yan et al , 2022, the excitation of the H(n = 2) state is dominated by radiative excitation and the population of H( 2p) is mostly determined by the Lyα intensity through…”

Section: Lyα Radiative Transfer Excited-state H and Associatedmentioning

confidence: 64%

A Hydrodynamic Study of the Escape of Metal Species and Excited Hydrogen from the Atmosphere of the Hot Jupiter WASP-121b

Huang

¹

,

Koskinen

²

,

Lavvas

³

et al. 2023

ApJ

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In the near-UV and optical transmission spectrum of the hot Jupiter WASP-121b, recent observations have detected strong absorption features of Mg, Fe, Ca, and Hα, extending outside of the planet’s Roche lobe. Studying these atomic signatures can directly trace the escaping atmosphere and constrain the energy balance of the upper atmosphere. To understand these features, we introduce a detailed forward model by expanding the capability of a one-dimensional model of the upper atmosphere and hydrodynamic escape to include important processes of atomic metal species. The hydrodynamic model is coupled to a Lyα Monte Carlo radiative transfer calculation to simulate the excited hydrogen population and associated heating/ionization effects. Using this model, we interpret the detected atomic features in the transmission spectrum of WASP-121b and explore the impact of metals and excited hydrogen on its upper atmosphere. We demonstrate the use of multiple absorption lines to impose stronger constraints on the properties of the upper atmosphere than the analysis of a single transmission feature can provide. In addition, the model shows that line broadening due to atmospheric outflow driven by Roche lobe overflow is necessary to explain the observed line widths and highlights the importance of the high mass-loss rate caused by Roche lobe overflow, which requires careful consideration of the structure of the lower and middle atmosphere. We also show that metal species and excited-state hydrogen can play an important role in the thermal and ionization balance of ultrahot Jupiter thermospheres.

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“…With its extremely low density and a uniquely large-scale height, HAT-P-67b is an exceptional target to characterize the transition region between hot and ultrahot giants. Additionally, if its outflow is confirmed, HAT-P-67b may become a prime target for simultaneous characterization of two probes of atmospheric escape (e.g., Czesla et al 2022;Yan et al 2022) and for studies of the morphology of hydrodynamic winds (e.g., McCann et al 2019;MacLeod & Oklopčić 2022).…”

Section: Discussionmentioning

confidence: 99%

“…Additionally, CARMENES provides simultaneous access to Hα and the 1083 nm triplet of metastable helium. Joint modeling of these two signals can improve constraints on the outflow parameters (Yan et al 2022). Lastly, planets receiving high levels of stellar irradiation are often found to host high-velocity winds flowing from their daysides to their nightsides (e.g., Snellen et al 2010;Casasayas-Barris et al 2019;Nugroho et al 2020;Bello-Arufe et al 2022b;Kesseli et al 2022;Prinoth et al 2022;Zhang et al 2022), driven by large day-to-night heating variations (Showman et al 2013;Komacek & Showman 2016).…”

Section: Introductionmentioning

confidence: 99%

Transmission Spectroscopy of the Lowest-density Gas Giant: Metals and a Potential Extended Outflow in HAT-P-67b

Bello-Arufe

¹

,

Knutson

²

,

Mendonça

³

et al. 2023

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Extremely low-density exoplanets are tantalizing targets for atmospheric characterization because of their promisingly large signals in transmission spectroscopy. We present the first analysis of the atmosphere of the lowest-density gas giant currently known, HAT-P-67b. This inflated Saturn-mass exoplanet sits at the boundary between hot and ultrahot gas giants, where thermal dissociation of molecules begins to dominate atmospheric composition. We observed a transit of HAT-P-67b at high spectral resolution with CARMENES and searched for atomic and molecular species using cross-correlation and likelihood mapping. Furthermore, we explored potential atmospheric escape by targeting Hα and the metastable helium line. We detect Ca ii and Na i with significances of 13.2σ and 4.6σ, respectively. Unlike in several ultrahot Jupiters, we do not measure a day-to-night wind. The large line depths of Ca ii suggest that the upper atmosphere may be more ionized than models predict. We detect strong variability in Hα and the helium triplet during the observations. These signals suggest the possible presence of an extended planetary outflow that causes an early ingress and late egress. In the averaged transmission spectrum, we measure redshifted absorption at the ∼3.8% and ∼4.5% level in the Hα and He i triplet lines, respectively. From an isothermal Parker wind model, we derive a mass-loss rate of M ̇ ∼ 10 13 g s − 1 and an outflow temperature of T ∼ 9900 K. However, due to the lack of a longer out-of-transit baseline in our data, additional observations are needed to rule out stellar variability as the source of the Hα and He signals.

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Modeling the Hα and He 10830 Transmission Spectrum of WASP-52b

Cited by 16 publications

References 118 publications

The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation

The Upper Edge of the Neptune Desert Is Stable Against Photoevaporation

A Hydrodynamic Study of the Escape of Metal Species and Excited Hydrogen from the Atmosphere of the Hot Jupiter WASP-121b

Transmission Spectroscopy of the Lowest-density Gas Giant: Metals and a Potential Extended Outflow in HAT-P-67b

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