scholarly journals UV Absorption by Silicate Cloud Precursors in Ultra-hot Jupiter WASP-178b

2021 ◽  
Author(s):  
Joshua Lothringer ◽  
David Sing ◽  
Zafar Rustamkulov ◽  
Hannah Wakeford ◽  
Kevin Stevenson ◽  
...  
Keyword(s):  
Transmission Spectrum ◽  
Middle Atmosphere ◽  
Theoretical Models ◽  
Giant Planets ◽  
Cloud Formation ◽  
Spectral Features ◽  
Theoretical Expectation ◽  
Refractory Elements ◽  
Wavelength Absorption ◽  
Hot Jupiter

Abstract Aerosols have been found to be nearly ubiquitous in substellar atmospheres. Evidence for the composition and conditions whereby these aerosols form remains limited (Cushing et al. 2006, Saumon & Marley 2008, Burningham 2021). Theoretical models and observations of muted spectral features suggest that silicate clouds play an important role in exoplanets between at least 950 and 2,100 K (Gao et al. 2020). However, some giant planets are thought to be hot enough to avoid condensation of even the most refractory elements (Lothringer et al. 2018, Kitzmann et al. 2018). Here, we present the near-UV transmission spectrum of an ultra-hot Jupiter WASP-178b (~2,450 K), that exhibits significant NUV absorption indicating the presence of gaseous refractory elements in the middle atmosphere. This short-wavelength absorption is among the largest spectral features ever observed in an exoplanet in terms of atmospheric scale heights. Bayesian retrievals indicate the broadband UV feature on WASP-178b is caused by refractory elements including silicon and magnesium bearing species, which are the precursors to condensate clouds at lower temperatures. Silicon in particular has not been detected in exoplanets before, but the presence of SiO in WASP-178b is consistent with theoretical expectation as the dominant Si-bearing species at high temperatures. These observations allow us to re-interpret previous observations of HAT-P-41b and WASP-121b to suggest that silicate cloud formation begins on exoplanets with equilibrium temperatures between 1,950 and 2,350 K.

scholarly journals The optical transmission spectrum of the hot Jupiter HAT-P-32b: clouds explain the absence of broad spectral features?

2013 ◽  
Vol 436 (4) ◽  
pp. 2974-2988 ◽  
Author(s):  
N. P. Gibson ◽  
S. Aigrain ◽  
J. K. Barstow ◽  
T. M. Evans ◽  
L. N. Fletcher ◽  
...  
Keyword(s):  
Transmission Spectrum ◽  
Optical Transmission ◽  
Optical Transmission Spectrum ◽  
Spectral Features ◽  
Hot Jupiter

scholarly journals Understanding the atmospheric properties and chemical composition of the ultra-hot Jupiter HAT-P-7b

2019 ◽  
Vol 631 ◽  
pp. A79 ◽  
Author(s):  
Ch. Helling ◽  
N. Iro ◽  
L. Corrales ◽  
D. Samra ◽  
K. Ohno ◽  
...  
Keyword(s):  
Gas Phase ◽  
Local Equilibrium ◽  
Theoretical Models ◽  
Cloud Formation ◽  
Phase Curve ◽  
Large Temperature ◽  
Global Changes ◽  
Hot Jupiters ◽  
Dependent Observations ◽  
Hot Jupiter

Context. Of the presently known ≈3900 exoplanets, sparse spectral observations are available for ≈100. Ultra-hot Jupiters have recently attracted interest from observers and theoreticians alike, as they provide observationally accessible test cases. Confronting detailed theoretical models with observations is of preeminent importance in preparation for upcoming space-based telescopes. Aims. We aim to study cloud formation on the ultra-hot Jupiter HAT-P-7b, the resulting composition of the local gas phase, and how their global changes affect wavelength-dependent observations utilised to derive fundamental properties of the planet. Methods. We apply a hierarchical modelling approach as a virtual laboratory to study cloud formation and gas-phase chemistry. We utilise 97 vertical 1D profiles of a 3D GCM for HAT-P-7b to evaluate our kinetic cloud formation model consistently with the local equilibrium gas-phase composition. We use maps and slice views to provide a global understanding of the cloud and gas chemistry. Results. The day/night temperature difference on HAT-P-7b (ΔT ≈ 2500 K) causes clouds to form on the nightside (dominated by H2/He) while the dayside (dominated by H/He) retains cloud-free equatorial regions. The cloud particles vary in composition and size throughout the vertical extension of the cloud, but also globally. TiO2[s]/Al2O3[s]/CaTiO3[s]-particles of cm-sized radii occur in the higher dayside-latitudes, resulting in a dayside dominated by gas-phase opacity. The opacity on the nightside, however, is dominated by 0.01…0.1μm particles made of a material mix dominated by silicates. The gas pressure at which the atmosphere becomes optically thick is ~10−4 bar in cloudy regions, and ~0.1 bar in cloud-free regions. Conclusions. HAT-P-7b features strong morning/evening terminator asymmetries, providing an example of patchy clouds and azimuthally-inhomogeneous chemistry. Variable terminator properties may be accessible by ingress/egress transmission photometry (e.g., CHEOPS and PLATO) or spectroscopy. The large temperature differences of ≈2500 K result in an increasing geometrical extension from the night- to the dayside. The H2O abundance at the terminator changes by <1 dex with altitude and ≲0.3 dex (a factor of 2) across the terminator for a given pressure, indicating that H2O abundances derived from transmission spectra can be representative of the well-mixed metallicity at P ≳ 10 bar. We suggest the atmospheric C/O as an important tool to trace the presence and location of clouds in exoplanet atmospheres. The atmospheric C/O can be sub- and supersolar due to cloud formation. Phase curve variability of HAT-P-7b is unlikely to be caused by dayside clouds.

Modelling the influence of high-energy radiation on the atmospheric composition of the hot Jupiter HD 189733b

2021 ◽  
Author(s):  
Patrick Barth ◽  
Christiane Helling ◽  
Eva E. Stüeken ◽  
Vincent Bourrier ◽  
Nathan Mayne ◽  
...  
Keyword(s):  
Cosmic Rays ◽  
High Energy ◽  
Galactic Cosmic Rays ◽  
Energetic Particles ◽  
Atmospheric Composition ◽  
Cloud Formation ◽  
Fine Grid ◽  
High Energy Radiation ◽  
Energy Radiation ◽  
Hot Jupiter

&lt;p&gt;Hot Jupiters provide valuable natural laboratories for studying potential contributions of high-energy radiation to prebiotic synthesis in the atmospheres of exoplanets. HD 189733b, a hot Jupiter orbiting a K star, is one of the most studied and best observed exoplanets. We combine XUV observations and 3D climate simulations to model the atmospheric composition and kinetic chemistry with the STAND2019 network. We show how XUV radiation, cosmic rays (CR), and stellar energetic particles (SEP) influence the chemistry of the atmosphere. We explore the effect that the change in the XUV radiation has over time, and we identify key atmospheric signatures of an XUV, CR, and SEP influx. 3D simulations of HD 189733b's atmosphere with the 3D Met Office Unified Model provide a fine grid of pressure-temperature profiles, consistently taking into account kinetic cloud formation. We apply &lt;em&gt;HST&lt;/em&gt; and &lt;em&gt;XMM-Newton/Swift&lt;/em&gt; observations obtained by the MOVES programmewhich provide combined X-ray and ultraviolet (XUV) spectra of the host star HD 189733 at 4 different points in time. We find that the differences in the radiation field between the irradiated dayside and the shadowed nightside lead to stronger changes in the chemical abundances than the variability of the host star's XUV emission. We identify ammonium (NH&lt;sub&gt;4&lt;/sub&gt;&lt;sup&gt;+&lt;/sup&gt;) and oxonium (H&lt;sub&gt;3&lt;/sub&gt;O&lt;sup&gt;+&lt;/sup&gt;) as fingerprint ions for the ionization of the atmosphere by both galactic cosmic rays and stellar particles. All considered types of high-energy radiation have an enhancing effect on the abundance of key organic molecules such as hydrogen cyanide (HCN), formaldehyde (CH&lt;sub&gt;2&lt;/sub&gt;O), and ethylene (C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;4&lt;/sub&gt;). The latter two are intermediates in the production pathway of the amino acid glycine (C&lt;sub&gt;2&lt;/sub&gt;H&lt;sub&gt;5&lt;/sub&gt;NO&lt;sub&gt;2&lt;/sub&gt;) and abundant enough to be potentially detectable by &lt;em&gt;JWST&lt;/em&gt;. Ultimately, we show that high energy processes potentially play an important role in prebiotic chemistry.&lt;/p&gt;&lt;p&gt;P Barth et al., MOVES IV. Modelling the influence of stellar XUV-flux, cosmic rays, and stellar energetic particles on the atmospheric composition of the hot Jupiter HD&amp;#160;189733b, &lt;em&gt;Monthly Notices of the Royal Astronomical Society&lt;/em&gt;, in press, DOI:10.1093/mnras/staa3989&lt;/p&gt;

1D atmospheric modelling of K2-18b

2020 ◽  
Author(s):  
Doriann Blain ◽  
Benjamin Charnay ◽  
Bruno Bézard
Keyword(s):  
Transmission Spectrum ◽  
Atmospheric Model ◽  
Eddy Diffusion ◽  
Atmospheric Composition ◽  
Cloud Formation ◽  
Internal Source ◽  
Forward Modelling ◽  
Space Telescopes ◽  
Eddy Diffusion Coefficient ◽  
High Metallicity

&lt;p&gt;The atmospheric composition of exoplanets with masses between 2 and 10 M&amp;#8853; is poorly known. In that regard, the sub-Neptune K2-18b offers a valuable opportunity for the characterisation of such atmospheres under Earth-like stellar irradiation. Previous analyses of its transmission spectrum from the Kepler, Hubble and Spitzer space telescopes data using both retrieval algorithms and forward-modelling suggest the presence H&lt;sub&gt;2&lt;/sub&gt;O, as well as a low amount of CH&lt;sub&gt;4&lt;/sub&gt; in a H&lt;sub&gt;2&lt;/sub&gt;&amp;#8211;He atmosphere.&lt;/p&gt; &lt;p&gt;We present here simulations of the atmosphere of K2-18 b using Exo-REM, our self-consistent 1D atmospheric model &amp;#8212; recently adapted for transiting, high-metallicity giant exoplanets &amp;#8212; to study the atmosphere of K2-18b. We compared the transmission spectra computed by our model with the above-mentionned data (0.4 to 5 &amp;#956;m) to infer the planet atmospheric composition assuming a H&lt;sub&gt;2&lt;/sub&gt;&amp;#8211;He dominated atmosphere. We investigated the effect of irradiation, eddy diffusion coefficient, internal source, clouds, C/O ratio and metallicity on the atmospheric structure and transit spectrum.&amp;#160;&lt;br /&gt;We will put an emphasis of the relative contributions of the various absorbers to the transmission spectrum. We will show that our simulations favor atmospheric metallicities from 100 to 200 times solar. We will also discuss the possibility of a CH&lt;sub&gt;4&lt;/sub&gt;-depleted atmosphere and of liquid H&lt;sub&gt;2&lt;/sub&gt;O cloud formation.&lt;/p&gt;

scholarly journals Two Classes of Hot Jupiter Atmospheres

2008 ◽  
Vol 4 (S253) ◽  
pp. 247-253
Author(s):  
Jonathan J. Fortney
Keyword(s):  
Optical Spectra ◽  
Giant Planets ◽  
Potential Importance ◽  
Night Temperature ◽  
Solar Composition ◽  
The Difference ◽  
Temperature Inversions ◽  
Hot Jupiter

AbstractWe highlight the potential importance of gaseous TiO and VO opacity on the highly irradiated close-in giant planets. The day-side atmospheres of these planets may naturally fall into two classes that are somewhat analogous to the M- and L-type dwarfs. Those that are warm enough to have appreciable opacity due to TiO and VO gases we term the “pM Class” planets, and those that are cooler, such that Ti and V are predominantly in solid condensates, we term “pL Class” planets. The optical spectra of pL Class planets are dominated by neutral atomic Na and K absorption. We discuss a connection between temperature inversions and large day/night temperature contrasts for the pM Class planets. Around a Sun-like primary, for solar composition, this boundary likely occurs at ~0.04-0.05 AU, but we discuss important uncertainties. The difference in the observed day/night contrast between υ And b (pM Class) and HD 189733b (pL Class) is naturally explained in this scenario.

scholarly journals A spectroscopic survey of FHB stars near the south galactic pole

2009 ◽  
Vol 5 (S262) ◽  
pp. 422-423
Author(s):  
Silvia Rossi ◽  
Roberto Ortiz ◽  
Ronald Wilhelm ◽  
Roberto Costa ◽  
Timothy C. Beers
Keyword(s):  
High Probability ◽  
Main Sequence ◽  
Galactic Plane ◽  
Theoretical Models ◽  
Spectral Features ◽  
Horizontal Branch ◽  
Atmospheric Parameters ◽  
The South ◽  
Medium Resolution

AbstractWe present the results of a medium-resolution spectroscopic survey of 43 field horizontal-branch (FHB) candidates carried out near the south galactic pole, selected from the original list of FHB candidates compiled by Beers et al. (2007). The observation list includes only stars classified as “high-probability” candidates, according to their 2MASS infrared colours. Atmospheric parameters of some stars have been obtained by comparing some spectral features with theoretical models provided by Kurucz (1993). A comparison between the grid of model atmospheres with some parameters of the Hδ line allowed the determination of log g, whilst [Fe/H] was estimated by the equivalent widths of the MgII 4481 and Caii lines. About 77% of the sample have been classified as FHB stars, 10% as subdwarfs, whilst the remaining 13% are probably main-sequence A-type stars far from the Galactic plane.

scholarly journals Unprecedented accurate abundances: signatures of other Earths?

2009 ◽  
Vol 5 (S265) ◽  
pp. 412-415
Author(s):  
Jorge Meléndez ◽  
Martin Asplund ◽  
Bengt Gustafsson ◽  
David Yong ◽  
Iván Ramírez
Keyword(s):  
Chemical Composition ◽  
Giant Planets ◽  
Elemental Abundance ◽  
The Sun ◽  
Volatile Elements ◽  
Solar Abundance ◽  
Abundance Pattern ◽  
Refractory Elements ◽  
Solar Type ◽  
Solar Analogs

AbstractFor more than 140 years the chemical composition of our Sun has been considered typical of solar-type stars. Our highly differential elemental abundance analysis of unprecedented accuracy (~0.01 dex) of the Sun relative to solar twins, shows that the Sun has a peculiar chemical composition with a ≈20% depletion of refractory elements relative to the volatile elements in comparison with solar twins. The abundance differences correlate strongly with the condensation temperatures of the elements. A similar study of solar analogs from planet surveys shows that this peculiarity also holds in comparisons with solar analogs known to have close-in giant planets while the majority of solar analogs without detected giant planets show the solar abundance pattern. The peculiarities in the solar chemical composition can be explained as signatures of the formation of terrestrial planets like our own Earth.

scholarly journals Influence of gravity waves on the climatology of high-altitude Martian carbon dioxide ice clouds

2018 ◽  
Author(s):  
Erdal Yiğit ◽  
Alexander S. Medvedev ◽  
Paul Hartogh
Keyword(s):  
Carbon Dioxide ◽  
High Altitude ◽  
Gravity Waves ◽  
General Circulation ◽  
Middle Atmosphere ◽  
Circulation Model ◽  
Upper Atmosphere ◽  
Cloud Formation ◽  
Ice Clouds ◽  
Ice Cloud

Abstract. Carbon dioxide (CO2) ice clouds have been routinely observed in the middle atmosphere of Mars. However, there are still uncertainties concerning physical mechanisms that control their altitude, geographical, and seasonal distributions. Using the Max Planck Institute Martian General Circulation Model (MPI-MGCM), incorporating a state-of-the-art whole atmosphere subgrid-scale gravity wave parameterization (Yiğit et al., 2008), we demonstrate that internal gravity waves generated by lower atmospheric weather processes have wide reaching impact on the Martian climate. Globally, GWs cool the upper atmosphere of Mars by ~10 % and facilitate high-altitude CO2 ice cloud formation. CO2 ice cloud seasonal variations in the mesosphere and the mesopause region appreciably coincide with the spatio-temporal variations of GW effects, providing insight into the observed distribution of clouds. Our results suggest that GW propagation and dissipation constitute a necessary physical mechanism for CO2 ice cloud formation in the Martian upper atmosphere during all seasons.

scholarly journals Comparison of the CMAM30 data set with ACE-FTS and OSIRIS: polar regions

2015 ◽  
Vol 15 (8) ◽  
pp. 11179-11221
Author(s):  
D. Pendlebury ◽  
D. Plummer ◽  
J. Scinocca ◽  
P. Sheese ◽  
K. Strong ◽  
...  
Keyword(s):  
Water Vapour ◽  
Southern Hemisphere ◽  
Atmospheric Chemistry ◽  
Middle Atmosphere ◽  
Imaging System ◽  
Polar Vortex ◽  
Cloud Formation ◽  
Polar Regions ◽  
Data Set ◽  
Chemical Tracers

Abstract. CMAM30 is a 30 year data set extending from 1979 to 2010 that is generated using a version of the Canadian Middle Atmosphere Model (CMAM) in which the winds and temperatures are relaxed to the Interim Reanalysis product from the European Centre Medium-Range for Weather Forecasts (ERA-Interim). The data set has dynamical fields that are very close to the reanalysis below 1 hPa and chemical tracers that are self-consistent with respect to the model winds and temperature. The chemical tracers are expected to be close to actual observations. The data set is here compared to two satellite records – the Atmospheric Chemistry Experiment Fourier Transform Spectometer and the Odin Optical Spectrograph and InfraRed Imaging System – for the purpose of validating the temperature, ozone, water vapour and methane fields. Data from the Aura Microwave Limb Sounder is also used for validation of the chemical processing in the polar vortex. It is found that the CMAM30 temperature is warm by up to 5 K in the stratosphere, with a low bias in the mesosphere of ~ 5–15 K. Ozone is reasonable (± 15%) except near the tropopause globally, and in the Southern Hemisphere winter polar vortex. Water vapour is consistently low by 10–20%, with corresponding high methane of 10–20%, except in the Southern Hemisphere polar vortex. Discrepancies in this region are shown to stem from the treatment of polar stratospheric cloud formation in the model.

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