Exploring super-Earth surfaces: Albedo of near-airless magma ocean planets and topography

Modirrousta-Galian, Darius; Itō, Yūichi; Micela, G.

doi:10.1016/j.icarus.2020.114175

Cited by 16 publications

(13 citation statements)

References 124 publications

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“…where R å is the stellar radius, a is the semimajor axis, and A is the Bond albedo. To keep in line with other studies, we adopt a standard Bond albedo of A = 0.3 (Bonfils et al 2018), although we are aware that the albedo is highly sensitive to the planetary properties and could therefore vary significantly (e.g., Marley et al 1999;Modirrousta-Galian et al 2021). For the equilibrium temperature we use T eq = 520 ± 44 K, where the uncertainty comes from the error propagation on the stellar parameters and the planetʼs semimajor axis from Table 1.…”

Section: Temperature-pressure Profilementioning

confidence: 99%

ARES.* V. No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

Mugnai

Modirrousta-Galian

Edwards

et al. 2021

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We present a study on the spatially scanned spectroscopic observations of the transit of GJ 1132 b, a warm (∼500 K) super-Earth (1.13 R ⊕ ) that was obtained with the G141 grism (1.125-1.650 μm) of the Wide Field Camera 3 (WFC3) on board the Hubble Space Telescope. We used the publicly available Iraclis pipeline to extract the planetary transmission spectra from the five visits and produced a precise transmission spectrum. We analyzed the spectrum using the TauREx3 atmospheric retrieval code, with which we show that the measurements do not contain molecular signatures in the investigated wavelength range and are best fit with a flat-line model. Our results suggest that the planet does not have a clear primordial, hydrogen-dominated atmosphere. Instead, GJ 1132 b could have a cloudy hydrogen-dominated atmosphere, have a very enriched secondary atmosphere, be airless, or have a tenuous atmosphere that has not been detected. Due to the narrow wavelength coverage of WFC3, these scenarios cannot be distinguished yet, but the James Webb Space Telescope may be capable of detecting atmospheric features, although several observations may be required to provide useful constraints.Unified Astronomy Thesaurus concepts: Exoplanet atmospheres (487); Astronomy data analysis (1858); Hubble Space Telescope (761); Exoplanets (498)

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Section: Temperature-pressure Profilementioning

confidence: 99%

ARES.* V. No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

Mugnai

Modirrousta-Galian

Edwards

et al. 2021

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“…The composition and dynamics of rocky exoplanet atmosphere are currently receiving considerable attention (Ito et al 2015;Madhusudhan 2019;Modirrousta-Galian et al 2021). This is partially due to the imminent arrival of several next-generation telescopes, both space and ground based, which have the characterisation of exoplanet atmospheres in their remit.…”

Section: Introductionmentioning

confidence: 99%

Idealised 3D simulations of diabatically forced Ledoux convection

Daley-Yates

Padioleau

Tremblin

et al. 2021

A&A

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Aims. We investigate the impact of dimensionality, resolution, and long timescales on convective numerical simulations forced by thermo-compositional diabatic processes. We focus our study on simulations that are stable to the Schwarzschild criterion but unstable to the Ledoux one (i.e. simulations with a stabilising temperature gradient and a destabilising mean-molecular-weight gradient). We aim to establish the possibility of a reduced temperature gradient in such setups. Methods. A suite of 3D simulations incorporating both time series and convergence studies were conducted using a high-performance numerical hydrodynamic code. We used, as a simplified and idealised test case, a sample region of the secondary atmosphere of a hot rocky exoplanet, of the order of the scale height of the system, within which the chemical transition CO + O ↔ CO2 could occur. Newtonian cooling was employed to force an equilibrium temperature, and a chemical source term was used to maintain a negative mean-molecular-weight gradient in the vertical direction. Results. Our results demonstrate that a mean-molecular-weight gradient and a chemical source term can reduce the atmosphere temperature gradient, a result that does not converge away with resolution and is stable when exploring long timescales. Simulations in two dimensions are prone to the development of shear modes, as already seen in the literature for double-diffusive convection. The 3D convective steady state is not impacted by these shear modes, suggesting that this phenomenon is linked to the dimensionality of the problem. We also show that the presence of the reduced temperature gradient is a function of the forcing timescales, disappearing if the chemical forcing is too slow. We find that the above transition leads to a bifurcation of the atmosphere’s temperature profile when the chemical forcing is fast. Such a bifurcation is reminiscent of the bifurcation seen in the boiling crisis for steam or liquid convection. Conclusions. With the reduced temperature gradient in these idealised setups, there exists the possibility of an analogy of the reddening (currently observed in the spectra of brown dwarfs) in the spectra of rocky exoplanet atmospheres. This possibility needs, however, to be checked with detailed 1D models in order to precisely characterise the equilibrium thermal and compositional gradients, the thermal and compositional forcing timescales, and the impact of a realistic equation of state to, in turn, assess if the regime identified here will develop in realistic situations. However, the possibility of this reddening cannot be excluded a priori. This prediction is new for terrestrial atmospheres and represents strong motivation for the use of diabatic models when analysing the atmospheric spectra of rocky exoplanets that will be observed with, for example, the James Webb Space Telescope.

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“…However there was some evidence to suggest that WASP-47 e's geometric albedo could also be as low as WASP-47 b, but a wide range of geometric albedo solutions were also found. Contrary to this, Modirrousta-Galian et al (2021) found that high spherical albedos for super-Earths could be explained by molten Fe-rich magma oceans on the surface of ultra-short period worlds (Rouan et al 2011).…”

Section: Fundamental Properties Of Ourmentioning

confidence: 67%

The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys

Clark,

Wright,

Wittenmyer

et al. 2021

Preprint

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Pioneering photometric, astrometric, and spectroscopic surveys are helping exoplanetary scientists better constrain the fundamental properties of stars within our galaxy, and the planets these stars host. In this study, we use the third data release from the stellar spectroscopic GALAH Survey, coupled with astrometric data of eDR3 from the Gaia satellite, and other data from NASA's Exoplanet Archive, to refine our understanding of 279 confirmed and candidate exoplanet host stars and their exoplanets. This homogenously analysed data set comprises 105 confirmed exoplanets, along with 146 K2 candidates, 95 TESS Objects of Interest (TOIs) and 52 Community TOIs (CTOIs). Our analysis significantly shifts several previously (unknown) planet parameters while decreasing the uncertainties for others; Our radius estimates suggest that 35 planet candidates are more likely brown dwarfs or stellar companions due to their new radius values. We are able to refine the radii and masses of WASP-47 e, K2-106 b, and CoRoT-7 b to their most precise values yet, to less than 2.3% and 8.5% respectively. We also use stellar rotational values from GALAH to show that most planet candidates will have mass measurements that will be tough to obtain with current ground-based spectrographs. With GALAH's chemical abundances, we show through chemo-kinematics that there are five planet-hosts that are associated with the galaxy's thick disc, including NGTS-4, K2-183 and K2-337. Finally, we show there is no statistical difference between the chemical properties of hot Neptune and hot rocky exoplanet hosts, with the possibility that short-period rocky worlds might be the remnant cores of hotter, gaseous worlds.

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Exploring super-Earth surfaces: Albedo of near-airless magma ocean planets and topography

Cited by 16 publications

References 124 publications

ARES.* V. No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

ARES.* V. No Evidence For Molecular Absorption in the HST WFC3 Spectrum of GJ 1132 b

Idealised 3D simulations of diabatically forced Ledoux convection

The GALAH Survey: Improving our understanding of confirmed and candidate planetary systems with large stellar surveys

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