Signatures of strong magnetization and a metal-poor atmosphere for a Neptune-sized exoplanet

Ben‐Jaffel, Lotfi; Ballester, G. E.; Muñoz, A. García; Lavvas, P.; Sing, David K.; Sanz-Forcada, J.; Cohen, Ofer; Kataria, Tiffany; Henry, Gregory W.; Buchhave, Lars A.; Mikal-Evans, Thomas; Wakeford, Hannah R.; López‐Morales, Mercedes

doi:10.1038/s41550-021-01505-x

Cited by 49 publications

(15 citation statements)

References 95 publications

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“…While there have been no direct measurements of exoplanet magnetic field strength yet, several indirect methods can offer constraints for particular planets. Recently, Ben-Jaffel et al (2021) detected the magnetosphere of the warm Neptune HAT-P-11b and estimated the equatorial magnetic field strength to be between 1 and 5 G. Magnetic planet star interactions, specifically Calcium II K emission, have also been used to indirectly estimate the surface magnetic fields of HJs in the range of 10-100 G (Cauley et al 2019). Variability in hotspot location has been found in 3D nonideal MHD models, leading Rogers (2017) to estimate a minimum magnetic field strength of 6 Gauss for the UHJ HAP-P-7b, in order to explain the observed variability on that planet (it should be noted, however, that recent work from Lally & Vanderburg 2022 finds that the observed variation could be due to nonatmospheric sources).…”

Section: Introductionmentioning

confidence: 99%

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Beltz

Rauscher

Kempton

et al. 2022

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Ultrahot Jupiters are ideal candidates to explore with high-resolution emission spectra. Detailed theoretical studies are necessary to investigate the range of spectra that we can expect to see from these objects throughout their orbit, because of the extreme temperature and chemical longitudinal gradients that exist across their dayside and nightside regions. Using previously published 3D general circulation models of WASP-76b with different treatments of magnetic drag, we postprocess the 3D atmospheres to generate high-resolution emission spectra for two wavelength ranges, throughout the planet’s orbit. We find that the high-resolution emission spectra vary strongly as a function of phase, at times showing emission features, absorption features, or both, which are a direct result of the 3D structure of the planet. At phases exhibiting both emission and absorption features, the Doppler shift differs in direction between the two spectral features, making them differentiable, instead of canceling each other out. Through the use of cross correlation, we find different patterns in net Doppler shift for models with different treatments of drag: the nightside spectra show opposite signs in their Doppler shift, while the dayside phases display a reversal in the trend of net shift with phase. Finally, we caution researchers against using a single spectral template throughout the planet’s orbit; this can bias the corresponding net Doppler shift returned, as it can pick up on a bright region on the edge of the planet disk that is highly redshifted or blueshifted.

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Section: Introductionmentioning

confidence: 99%

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Beltz

Rauscher

Kempton

et al. 2022

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“…Notably, atmospheric expansion and hydrodynamic escape, as well as thermospheric and ionospheric layers, temperatures, and winds, have all been measured or inferred for exoplanets using tracers such as He I and Na I, among others (see Vidal-Madjar et al 2011;Spake et al 2018;Seidel et al 2020;Cauley et al 2021;Allart et al 2019). Recently, observations of ionospheric species have been described as evidence for the possible first detection of an exoplanetary magnetic field (Ben-Jaffel et al 2021).…”

Section: Introductionmentioning

confidence: 99%

Limits on the Auroral Generation of H₃ ⁺ in Brown Dwarf and Extrasolar Giant Planet Atmospheres with the Keck Near Infrared Echelle Spectrograph

Gibbs

Fitzgerald

2022

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The molecular ion H3 + is a potentially powerful tracer of the ionospheres and thermal structures of Jovian planets but has never been detected in a planetary mass object outside of the solar system. Models predict that H3 + emission driven by EUV flux and solar wind on hot Jupiters, or by powerful aurorae on brown dwarfs, will be between 102 and 105 × more intense than that of Jupiter. If optimal conditions for the production of emission do exist, the emission may be detectable by current ground-based instruments or in the near future. We present the first search for H3 + line emission in brown dwarfs with Keck Near Infrared Echelle Spectrograph L′ high-resolution spectroscopy. Additionally, we survey stars hosting giant planets at semimajor axes near 0.1–0.2 au, which models suggest may be the best planetary targets. No candidate H3 + emission is found. The limits we place on the emission of H3 + from brown dwarfs indicate that auroral generation of H3 + in these environments likely does not linearly scale from the processes found on Jupiter, plausibly due to deeper atmospheric penetration by precipitating auroral electrons. Detection of H3 + emission in brown dwarfs may be possible with the James Webb Space Telescope, or future 33 m class telescopes.

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“…In other words, they are thought to be photoevaporated and eventually escape the planet. The mass-loss rates of atmospheric escape can be as high as 10 9 -10 13 g s −1 (Shaikhislamov et al 2020;Ben-Jaffel et al 2021;Czesla et al 2022). This process can have important ramifications for the planetary composition, evolution, and even the population of planets as a whole (Fulton et al 2017;Fulton & Petigura 2018).…”

Section: Introductionmentioning

confidence: 99%

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

Yan

Seon

Guo

et al. 2022

ApJ

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Escaping atmosphere has been detected by the excess absorption of Lyα, Hα and He triplet (λ10830) lines. Simultaneously modeling the absorption of the Hα and He λ10830 lines can provide useful constraints about the exoplanetary atmosphere. In this paper, we use a hydrodynamic model combined with a non−local thermodynamic model and a new Monte Carlo simulation model to obtain the H(2) and He(23 S) populations. The Monte Carlo simulations of Lyα radiative transfer are performed with assumptions of a spherical stellar Lyα radiation and a spherical planetary atmosphere, for the first time, to calculate the Lyα mean intensity distribution inside the planetary atmosphere, necessary in estimating the H(2) population. We model the transmission spectra of the Hα and He λ10830 lines simultaneously in hot Jupiter WASP-52b. We find that models with many different H/He ratios can reproduce the Hα observations well if the host star has (1) a high X-ray and extreme-ultraviolet (XUV) flux (F XUV) and a relatively low X-ray fraction in XUV radiation (β m ) or (2) a low F XUV and a high β m . The simulations of the He λ10830 triplet suggest that a high H/He ratio (∼98/2) is required to fit the observation. The models that fit both lines well confine F XUV to be about 0.5 times the fiducial value and β m to have a value around 0.3. The models also suggest that hydrogen and helium originate from the escaping atmosphere, and the mass-loss rate is about 2.8 × 1011 g s−1.

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Signatures of strong magnetization and a metal-poor atmosphere for a Neptune-sized exoplanet

Cited by 49 publications

References 95 publications

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Limits on the Auroral Generation of H₃ ⁺ in Brown Dwarf and Extrasolar Giant Planet Atmospheres with the Keck Near Infrared Echelle Spectrograph

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

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Signatures of strong magnetization and a metal-poor atmosphere for a Neptune-sized exoplanet

Cited by 49 publications

References 95 publications

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Magnetic Drag and 3D Effects in Theoretical High-resolution Emission Spectra of Ultrahot Jupiters: the Case of WASP-76b

Limits on the Auroral Generation of H3 + in Brown Dwarf and Extrasolar Giant Planet Atmospheres with the Keck Near Infrared Echelle Spectrograph

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

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Limits on the Auroral Generation of H₃ ⁺ in Brown Dwarf and Extrasolar Giant Planet Atmospheres with the Keck Near Infrared Echelle Spectrograph