我们开发了一个新的一维光化学动力学代码，以解决平流层的化学和平流层加热在炎热的夏季。在这里，我们解决光学活性含S物种和CO2在1200 <T <2000 K。HS（巯基）和S2是由H2S光化学和热化学生成的高反应性物质，峰值丰度在1 - 10 mbar之间。S2吸收240~340 nm的紫外光，在T> 1200 K时金属度[SH]> 0时光学厚度较大。HS可能比S2更重要，因为在热木星的条件下，它通常比S2更丰富，并且它吸收的波长更红。我们使用分子理论来计算HS吸收光谱从稀疏的可用数据，并发现HS应强烈吸收之间的300和460 nm，在较长波长的吸收温度敏感。当这两种吸收体结合在一起时，辐射加热（每千克气体）的峰值为100微巴，对于一颗在0.032天文单位处绕着太阳双星轨道运行的类木行星来说，平流层总加热量约为8 x 10^4 W/m^2。总加热量对金属丰度不敏感。CO2混合比是金属丰度的一个良好的二次函数，当-0.3 <[M/H]<1.7时，其范围为1.6 x 10 ^-8~1.6 x 10 ^-4。CO2对日照、垂直混合、温度（1200 <T <2000 K）和重力不敏感。光化学计算证实，CO2应该证明是行星金属丰度的有用探针。
英文摘要：
We develop a new 1D photochemical kinetics code to address stratospheric chemistry and stratospheric heating in hot Jupiters. Here we address optically active S-containing species and CO2 at 1200 < T < 2000 K. HS (mercapto) and S2 are highly reactive species that are generated photochemically and thermochemically from H2S with peak abundances between 1-10 mbar. S2 absorbs UV between 240 and 340 nm and is optically thick for metallicities [SH] > 0 at T > 1200 K. HS is probably more important than S2, as it is generally more abundant than S2 under hot Jupiter conditions and it absorbs at somewhat redder wavelengths. We use molecular theory to compute an HS absorption spectrum from sparse available data and find that HS should absorb strongly between 300 and 460 nm, with absorption at the longer wavelengths being temperature sensitive. When the two absorbers are combined, radiative heating (per kg of gas) peaks at 100 microbars, with a total stratospheric heating of about 8 x 10^4 W/m^2 for a jovian planet orbiting a solar-twin at 0.032 AU. Total heating is insensitive to metallicity. The CO2 mixing ratio is a well-behaved quadratic function of metallicity, ranging from 1.6 x 10^-8 to 1.6 x 10^-4 for -0.3 < [M/H] < 1.7. CO2 is insensitive to insolation, vertical mixing, temperature (1200 < T <2000 K), and gravity. The photochemical calculations confirm that CO2 should prove a useful probe of planetary metallicity.
我们使用1D模型来解决光化学和可能的烟雾形成的照射温暖的木星，51波江座b。本计划的重点是碳，但硫的光化学结果是重要的。有机光化学烟雾的情况是有趣的，但缺乏令人信服的。如果有机烟雾形成，如果51 Eri b的垂直混合比木星弱，它们最有可能这样做，并且它们将在甲烷和水光解的高度以下被发现。更新颖的结果是，光化学将H $_2$ S转化为元素硫，在此处理为S $_8$。在较冷的模型中，S $_8$预计会凝结成固体硫颗粒的光学厚云，而在较暖的模型中，S $_8$与其他几种硫同素异形体一起保持蒸汽状态，这些硫同素异形体在视觉上引人注目，并且可能是可观察的。对于51 Eri b，有和没有冷凝硫的模型之间的分界线是在700 K的有效温度，这是在其实际有效温度的误差范围内;硫冷凝的局部温度在280和320 K之间。我们讨论的硫光化学反应非常普遍，应该在广泛的温度范围内的各种世界中发现，无论是比这里研究的650-750 K范围更冷还是更热，我们表明硫光化学反应的产物在紫外线辐射比51 Eri b弱几个数量级的行星上几乎同样丰富。
Sulfur gases significantly affect the photochemistry of planetary atmospheres in our Solar System, and are expected to be important components in exoplanet atmospheres. However, sulfur photochemistry in the context of exoplanets is poorly understood due to a lack of chemical-kinetics information for sulfur species under relevant conditions. Here, we study the photochemical role of hydrogen sulfide (H2S) in warm CO2-rich exoplanet atmospheres (800 K) by carrying out laboratory simulations. We find that H2S plays a significant role in photochemistry, even when present in the atmosphere at relati…
We aim at constraining the diffusive and advective transport processes in Jupiter's stratosphere. The IR spectrum recorded by Cassini/CIRS during the Jupiter flyby contains the fingerprints of several atmospheric compounds and allows probing its atmospheric composition. C2H2 and C2H6, the main compounds produced by methane photochemistry, were retrieved as a function of latitude at certain pressure levels. CIRS observations suggest a different meridional distribution for these two species, difficult to reconcile with their photochemical histories, which are thought to be coupled to the methane…
The high cosmic abundance and the intermediate volatility and chemical properties of sulfur allow the use of sulfur-bearing species as a tracer of the chemical processes in the atmospheres of hot Jupiter exoplanets. Nevertheless, despite its properties and relevance as a tracer of the giant planets' formation history, little attention has been paid to this species in the context of hot Jupiter atmospheres. Here we provide an overview of the abundances of sulfur-bearing species in hot Jupiter atmospheres under different conditions and explore their observability. We use the photochemical kineti…
We investigated whether sulfur-bearing species are present on the icy Galilean moon Callisto by analyzing eight near-infrared reflectance spectra collected over a wide range of sub-observer longitudes. We measured the band areas and depths of a 4-micron feature in these spectra, which has been attributed to sulfur dioxide (SO2), as well as carbonates, in previously collected datasets of this moon. All eight spectra we collected display the 4-micron band. The four spectra collected over Callisto's leading hemisphere display significantly stronger 4-micron bands compared to the four trailing hem…
We present and validate a new network of atmospheric thermo-chemical and photo-chemical sulfur reactions. We use a 1-D chemical kinetics model to investigate these reactions as part of a broader HCNO chemical network in a series of hot and warm Jupiters. We find that temperatures approaching $1400\,\mathrm{K}$ are favourable for the production of H2S and HS around $\mathrm{10^{-3}\,bar}$, the atmospheric level where detection by transit spectroscopy may be possible, leading to mixing ratios of around $10^{-6}$. At lower temperatures, down to $1000\,\mathrm{K}$, the abundance of S2 can be up to…
We have conducted laboratory experiments to study the chemistry in hot Jupiter atmospheres with C/O ratio of 0.35. We have compared our results with the ones obtained previously for atmospheres with a C/O ratio of 1 to investigate the influence of the C/O ratio on the chemistry and formation of photochemical organic aerosol. We found that the C/O ratio and the gas mixture compositions strongly influence the pathways responsible for the formation of CO2. Thermochemical reactions are primarily responsible for the formation of CO2 in low C/O ratio atmospheres, while photochemistry is the dominant…
We present a study of photochemical hazes of exoplanet atmospheres based on a self-consistent model including haze microphysics, disequilibrium chemistry, and radiative feedbacks. We derive the haze properties required to match HST observations of ten hot-Jupiters. HAT-P-12b, HD-189733b, HD-209458b and WASP-6b require haze mass fluxes between 5x10$^{-15}$ and 9x10$^{-12} g.cm^{-2}.s^{-1}$ to match the observations. WASP-12b and WASP-19b with equilibrium temperatures above 2000 K are incompatible with the presence of haze and are better fitted by heavy metals. HAT-P-1b and WASP-31b do not show …
Nitrogen as a Tracer of Giant Planet Formation. II.: Comprehensive Study of Nitrogen Photochemistry and Implications for Observing NH3 and HCN in Transmission and Emission Spectra
Photochemistry has the potential to substantially impact the atmospheric composition of exoplanets with consequences on the radiative transfer, thermal structure and dynamics of the atmospheres, particularly in UV-rich stellar environments. Here, we present the results of a first laboratory experimental simulation of photochemistry in carbon-rich exoplanet atmospheres at elevated temperatures. Evolution of gas-phase molecular composition was quantitatively monitored with infrared spectroscopy and mass spectrometry. We found that H2/CO gas compositions can change significantly from thermal equi…
A time-variable 1D photochemical model is used to study the distribution of stratospheric hydrocarbons as a function of altitude, latitude, and season on Uranus and Neptune. The results for Neptune indicate that in the absence of stratospheric circulation or other meridional transport processes, the hydrocarbon abundances exhibit strong seasonal and meridional variations in the upper stratosphere, but that these variations become increasingly damped with depth due to increasing dynamical and chemical time scales. At high altitudes, hydrocarbon mixing ratios are typically largest where the sola…
A Sulfur-Rich Atmosphere for the Young Jupiter Analog AF Lep b Reveals Significant Solid Accretion
University of California, Los Angeles（加州大学洛杉矶分校）；Northwestern University（西北大学）；University of California, Santa Cruz（加州大学圣克鲁兹分校）；University of California, San Diego（加州大学圣迭戈分校）；National Astronomical Observatory of Japan（日本国立天文台）；European Southern Observatory（欧洲南方天文台）；New Mexico State University（新墨西哥州立大学）
The elemental ratios of carbon, nitrogen, and oxygen in the atmospheres of hot Jupiters may hold clues to their formation locations in the protostellar disc. In this work, we adopt gas phase chemical abundances of C, N and O from several locations in a disc chemical kinetics model as sources for the envelope of the hot Jupiter HD 209458b and evolve the planet's atmospheric composition using a 1D chemical kinetics model, treating both vertical mixing and photochemistry. We consider two atmospheric pressure-temperature profiles, one with and one without a thermal inversion. From each of the resu…
The atmospheres of ultra-hot Jupiters are commonly considered to be at thermochemical equilibrium. We aim to provide disequilibrium chemistry maps for a global understanding of the chemistry in HAT-P-7b's atmosphere and assess the importance of disequilibrium chemistry on UHJs. We apply a hierarchical modelling approach utilising 97 1D atmospheric profiles from 3D GCM of HAT-P-7b. For each 1D profile, we evaluate our kinetic cloud formation model consistently with the local gas-phase composition in chemical equilibrium. We then evaluate quenching results from a zeroth-order approximation in co…
For solar-system objects, ultraviolet spectroscopy has been critical in identifying sources for stratospheric heating and measuring the abundances of a variety of hydrocarbon and sulfur-bearing species, produced via photochemical mechanisms, as well as oxygen and ozone. To date, less than 20 exoplanets have been probed in this critical wavelength range (0.2-0.4 um). Here we use data from Hubble's newly implemented WFC3 UVIS G280 grism to probe the atmosphere of the hot Jupiter HAT-P-41b in the ultraviolet through optical in combination with observations at infrared wavelengths. We analyze and …
We present an update of the open-source photochemical kinetics code VULCAN (Tsai et al. 2017; https://github.com/exoclime/VULCAN) to include C-H-N-O-S networks and photochemistry. Additional new features are advection transport, condensation, various boundary conditions, and temperature-dependent UV cross-sections. First, we validate our photochemical model for hot Jupiter atmospheres by performing an intercomparison of HD 189733b models between Moses et al. (2011), Venot et al. (2012), and VULCAN, to diagnose possible sources of discrepancy. Second, we set up a model of Jupiter extending from…
The low-resolution transmission spectra of ultra-hot Jupiters observed shortward of 0.5 microns indicate strong absorption at short-wavelengths. Previous explanations have included scattering, photochemistry, escaping metals, and disequilibrium chemistry. In this Letter, we show that slopes and features shortward of 0.5 microns can be caused by opacity not commonly considered in atmosphere models of exoplanets but guaranteed to be present if conditions are near chemical equilibrium including Fe I, Fe II, Ti I, Ni I, Ca I, Ca II, and SiO. Even relatively trace species (e.g., Cr I and Mn I) can …
We investigate the impact of photochemical hazes and disequilibrium gases on the thermal structure of hot-Jupiters, using a detailed 1-D radiative-convective model. We find that the inclusion of photochemical hazes results in major heating of the upper and cooling of the lower atmosphere. Sulphur containing species, such as SH, S$_2$ and S$_3$ provide significant opacity in the middle atmosphere and lead to local heating near 1 mbar, while OH, CH, NH, and CN radicals produced by the photochemistry affect the thermal structure near 1 $μ$bar. Furthermore we show that the modifications on the the…
A Fast, Parallelized, GPU-Accelerated Photochemical Model, XODIAC, with Built-in Equilibrium Chemistry and Multiple Chemical Networks for Exoplanetary Atmospheres
