A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

Cauley, P. Wilson; Redfield, Seth; Jensen, Adam G.

doi:10.3847/1538-3881/aa6a15

Cited by 86 publications

(58 citation statements)

References 105 publications

(197 reference statements)

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“…This is because the extended atmosphere of neutral hydrogen becomes almost entirely in the ground state at older ages. Our result agrees with the lack of absorption observed in the Hα transits of GJ436b (Cauley et al 2017), in spite of its impressively long and extended transit in Lyα (Kulow et al 2014;Ehrenreich et al 2015;Lavie et al 2017). This situation can occur when temperatures are not high enough to excite hydrogen.…”

Section: Hα Transitssupporting

confidence: 91%

Evolution of atmospheric escape in close-in giant planets and their associated Ly α and H α transit predictions

Allan

Vidotto

2019

Monthly Notices of the Royal Astronomical Society

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Strong atmospheric escape has been detected in several close-in exoplanets. As these planets consist mostly of hydrogen, observations in hydrogen lines, such as Lyα and Hα, are powerful diagnostics of escape. Here, we simulate the evolution of atmospheric escape of close-in giant planets and calculate their associated Lyα and Hα transits. We use a one-dimensional hydrodynamic escape model to compute physical properties of the atmosphere and a ray-tracing technique to simulate spectroscopic transits. We consider giant (0.3 and 1M jup ) planets orbiting a solar-like star at 0.045au, evolving from 10 to 5000 Myr. We find that younger giants show higher rates of escape, owing to a favourable combination of higher irradiation fluxes and weaker gravities. Less massive planets show higher escape rates (10 10 -10 13 g/s) than those more massive (10 9 -10 12 g/s) over their evolution. We estimate that the 1-M jup planet would lose at most 1% of its initial mass due to escape, while the 0.3-M jup planet, could lose up to 20%. This supports the idea that the Neptunian desert has been formed due to significant mass loss in low-gravity planets. At younger ages, we find that the mid-transit Lyα line is saturated at line centre, while Hα exhibits transit depths of at most 3 -4% in excess of their geometric transit. While at older ages, Lyα absorption is still significant (and possibly saturated for the lower mass planet), the Hα absorption nearly disappears. This is because the extended atmosphere of neutral hydrogen becomes predominantly in the ground state after ∼ 1.2 Gyr.

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Section: Hα Transitssupporting

confidence: 91%

Evolution of atmospheric escape in close-in giant planets and their associated Ly α and H α transit predictions

Allan

Vidotto

2019

Monthly Notices of the Royal Astronomical Society

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“…Cauley et al (2018) showed for HD189733b that the transit of active latitudes with bright facular and plage regions can cause emission feature in stellar lines. Also the strong magnetic field of HD189733 could have a significant effect on the emission in lines (Cauley et al 2017). Possibly related to the activity, we see an emissionlike feature in several stellar line cores as e.g.…”

Section: Stellar Activity Of Hd189733mentioning

confidence: 67%

“…Gray (Gray & Corbally 1994). For the calculation of the model atmospheres we used the Kurucz model (Kurucz 1970;Castelli & Kurucz 2004). For HD189733b, we used an effective temperature of 4875 K, a surface gravity of log g = 4.56 and a metallicity of dex -0.03.…”

Section: Center-to-limb Variationmentioning

confidence: 99%

The potassium absorption on HD189733b and HD209458b

Keles

Mallonn

Essen

et al. 2019

Monthly Notices of the Royal Astronomical Society: Letters

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In this work, we investigate the potassium excess absorption around 7699Å of the exoplanets HD189733b and HD209458b. For this purpose, we used high spectral resolution transit observations acquired with the 2 × 8.4m Large Binocular Telescope (LBT) and the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI). For a bandwidth of 0.8Å, we present a detection > 7-σ with an absorption level of 0.18 % for HD189733b. Applying the same analysis to HD209458b, we can set 3-σ upper limit of 0.09%, even though we do not detect a K-excess absorption. The investigation suggests that the K-feature is less present in the atmosphere of HD209458b than in the one of HD189733b. This comparison confirms previous claims that the atmospheres of these two planets must have fundamentally different properties.

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“…Transit absorption in the Hα line was also detected in several observations, as well as a pre-transit signature (Jensen et al 2012;Cauley et al 2015Cauley et al , 2016Cauley et al , 2017b. However, both in-and pre-transit absorption signatures were highly variable in time and strongly affected by stellar activity, making their interpretation difficult (Barnes et al 2016;Cauley et al 2017a;Kohl et al 2018). Furthermore, a 6-8% transit absorption in Xrays was reported by Poppenhaeger et al (2013), but more observations with higher sensitivity are needed to confirm this result (Marin & Grosso 2017).…”

Section: Introductionmentioning

confidence: 92%

Modeling the Lyαtransit absorption of the hot Jupiter HD 189733b

Odert

Еркаев

Kislyakova

et al. 2020

A&A

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Context. Hydrogen-dominated atmospheres of hot exoplanets expand and escape hydrodynamically due to the intense heating by the X-ray and extreme ultraviolet (XUV) irradiation of their host stars. Excess absorption of neutral hydrogen has been observed in the Lyα line during transits of several close-in gaseous exoplanets, indicating such extended atmospheres. Aims. For the hot Jupiter HD 189733b, this absorption shows temporal variability. Variations in stellar XUV emission and/or variable stellar wind conditions have been invoked to explain this effect. Methods. We apply a 1D hydrodynamic planetary upper atmosphere model and a 3D MHD stellar wind flow model to study the effect of variations of the stellar XUV irradiation and wind conditions at the planet's orbit on the neutral hydrogen distribution, including the production of energetic neutral atoms (ENAs), and the related Lyα transit signature. Results. We are able to reproduce the Lyα absorption observed in 2011 with a stellar XUV flux of 1.8×10 4 erg cm −2 s −1 , rather typical activity conditions for this star. Flares with parameters similar to the one observed 8 h before the transit are unlikely to have caused a significant modulation of the transit signature. We find that the resulting Lyα absorption is dominated by atmospheric broadening, whereas the contribution of ENAs is negligible. Thus, the absorption does not depend on the stellar wind parameters. Conclusions. Since the transit absorption can be modeled with typical stellar XUV and wind conditions, it is possible that the nondetection of the absorption in 2010 was affected by less-typical stellar activity conditions, such as a very different magnitude and/or shape of the star's spectral XUV emission, or temporal/spatial variations in Lyα affecting the determination of the transit absorption.

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A Decade of Hα Transits for HD 189733 b: Stellar Activity versus Absorption in the Extended Atmosphere

Cited by 86 publications

References 105 publications

Evolution of atmospheric escape in close-in giant planets and their associated Ly α and H α transit predictions

Evolution of atmospheric escape in close-in giant planets and their associated Ly α and H α transit predictions

The potassium absorption on HD189733b and HD209458b

Modeling the Lyαtransit absorption of the hot Jupiter HD 189733b

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