scholarly journals petitRADTRANS

2019 ◽  
Vol 627 ◽  
pp. A67 ◽  
Author(s):  
P. Mollière ◽  
J. P. Wardenier ◽  
R. van Boekel ◽  
Th. Henning ◽  
K. Molaverdikhani ◽  
...  
Keyword(s):  
High Resolution ◽  
Optical Constants ◽  
Emission Spectra ◽  
Transmission Spectra ◽  
Low Resolution ◽  
Cloud Particle ◽  
Hot Jupiters ◽  
Higher Temperature ◽  
Python Package

We present the easy-to-use, publicly available, Python package petitRADTRANS, built for the spectral characterization of exoplanet atmospheres. The code is fast, accurate, and versatile; it can calculate both transmission and emission spectra within a few seconds at low resolution (λ/Δλ = 1000; correlated-k method) and high resolution (λ/Δλ = 106; line-by-line method), using only a few lines of input instruction. The somewhat slower, correlated-k method is used at low resolution because it is more accurate than methods such as opacity sampling. Clouds can be included and treated using wavelength-dependent power law opacities, or by using optical constants of real condensates, specifying either the cloud particle size, or the atmospheric mixing and particle settling strength. Opacities of amorphous or crystalline, spherical or irregularly-shaped cloud particles are available. The line opacity database spans temperatures between 80 and 3000 K, allowing to model fluxes of objects such as terrestrial planets, super-Earths, Neptunes, or hot Jupiters, if their atmospheres are hydrogen-dominated. Higher temperature points and species will be added in the future, allowing to also model the class of ultra hot-Jupiters, with equilibrium temperatures Teq ≳ 2000 K. Radiative transfer results were tested by cross-verifying the low- and high-resolution implementation of petitRADTRANS, and benchmarked with the petitCODE, which itself is also benchmarked to the ATMO and Exo-REM codes. We successfully carried out test retrievals of synthetic JWST emission and transmission spectra (for the hot Jupiter TrES-4b, which has a Teq of ∼1800 K).

scholarly journals Alkaline exospheres of exoplanet systems: evaporative transmission spectra

2020 ◽  
Vol 497 (4) ◽  
pp. 5271-5291 ◽  
Author(s):  
Andrea Gebek ◽  
Apurva V Oza
Keyword(s):  
High Resolution ◽  
Cross Sections ◽  
Planetary Atmospheres ◽  
Hydrostatic Equilibrium ◽  
Transmission Spectra ◽  
Absorption Cross ◽  
Density Profiles ◽  
Hot Jupiters ◽  
Exoplanet Systems ◽  
Sodium And Potassium

ABSTRACT Hydrostatic equilibrium is an excellent approximation for the dense layers of planetary atmospheres, where it has been canonically used to interpret transmission spectra of exoplanets. Here, we exploit the ability of high-resolution spectrographs to probe tenuous layers of sodium and potassium gas due to their formidable absorption cross-sections. We present an atmosphere–exosphere degeneracy between optically thick and optically thin mediums, raising the question of whether hydrostatic equilibrium is appropriate for Na i lines observed at exoplanets. To this end we simulate three non-hydrostatic, evaporative, density profiles: (i) escaping, (ii) exomoon, and (iii) torus to examine their imprint on an alkaline exosphere in transmission. By analysing an evaporative curve of growth, we find that equivalent widths of $W_{\mathrm{Na D2}} \sim 1{\!-\!} 10\, \mathrm{m\mathring{\rm A}}$ are naturally driven by evaporation rates ∼103−105 kg s−1 of pure atomic Na. To break the degeneracy between atmospheric and exospheric absorption, we find that if the line ratio is D2/D1 ≳ 1.2 the gas is optically thin on average roughly indicating a non-hydrostatic structure of the atmosphere/exosphere. We show this is the case for Na i observations at hot Jupiters WASP-49b and HD189733b and also simulate their K i spectra. Lastly, motivated by the slew of metal detections at ultra-hot Jupiters, we suggest a toroidal atmosphere at WASP-76b and WASP-121b is consistent with the Na i data at present.

scholarly journals Modeling the High-resolution Emission Spectra of Clear and Cloudy Nontransiting Hot Jupiters

2021 ◽  
Vol 923 (1) ◽  
pp. 62
Author(s):  
Isaac Malsky ◽  
Emily Rauscher ◽  
Eliza M.-R. Kempton ◽  
Michael Roman ◽  
Deryl Long ◽  
...  
Keyword(s):  
High Resolution ◽  
Three Dimensional ◽  
Emission Spectra ◽  
Spectral Lines ◽  
Orbital Inclination ◽  
Hot Jupiters ◽  
Cloud Coverage ◽  
Doppler Shifts ◽  
Dimensional Models ◽  
Three Dimensional Models

Abstract The advent of high-resolution spectroscopy (R ≳ 25,000) as a method for characterization of exoplanet atmospheres has expanded our capability to study nontransiting planets, vastly increasing the number of planets accessible for observation. Many of the most favorable targets for atmospheric characterization are hot Jupiters, where we expect large spatial variation in physical conditions such as temperature, wind speed, and cloud coverage, making viewing geometry important. Three-dimensional models have generally simulated observational properties of hot Jupiters assuming edge-on viewing, which can be compared to observations of transiting planets, but neglected the large fraction of planets without nearly edge-on orbits. As the first investigation of how orbital inclination manifests in high-resolution emission spectra from three-dimensional models, we use a general circulation model to simulate the atmospheric structure of Upsilon Andromedae b, a typical nontransiting hot Jupiter with high observational interest, due the brightness of its host star. We compare models with and without clouds, and find that cloud coverage intensifies spatial variations by making colder regions dimmer and relatedly enhancing emission from the clear, hotter regions. This increases both the net Doppler shifts and the variation of the continuum flux amplitude over the course of the planet’s orbit. In order to accurately capture scattering from clouds, we implement a generalized two-stream radiative transfer routine for inhomogeneous multiple scattering atmospheres. As orbital inclination decreases, four key features of the high-resolution emission spectra also decrease in both the clear and cloudy models: (1) the average continuum flux level, (2) the amplitude of the variation in continuum with orbital phase, (3) net Doppler shifts of spectral lines, and (4) Doppler broadening in the spectra. Models capable of treating inhomogeneous cloud coverage and different viewing geometries are critical in understanding results from high-resolution emission spectra, enabling an additional avenue to investigate these extreme atmospheres.

scholarly journals Search for He I airglow emission from the hot Jupiter τ Boo b

2020 ◽  
Vol 641 ◽  
pp. A161
Author(s):  
Y. Zhang ◽  
I. A. G. Snellen ◽  
P. Mollière ◽  
F. J. Alonso-Floriano ◽  
R. K. Webb ◽  
...  
Keyword(s):  
High Resolution ◽  
Rest Frame ◽  
Emission Feature ◽  
Emission Lines ◽  
High Resolution Spectroscopy ◽  
Transmission Spectra ◽  
Hot Jupiters ◽  
Line Widths ◽  
Calar Alto ◽  
Metastable Triplet State

Context. It has been suggested that the helium absorption line at 10 830 Å that originates from the metastable triplet state 23S is an excellent probe for the extended atmospheres of hot Jupiters and their hydrodynamic escape processes. It has recently been detected in the transmission spectra of a handful of planets. The isotropic reemission will lead to helium airglow that may be observable at other orbital phases. Aims. We investigate the detectability of He I emission at 10 830 Å in the atmospheres of exoplanets using high-resolution spectroscopy. This would provide insights into the properties of the upper atmospheres of close-in gas giants. Methods. We estimated the expected strength of He I emission in hot Jupiters based on their transmission signal. We searched for the He I 10 830 Å emission feature in τ Boo b in three nights of high-resolution spectra taken by CARMENES at the 3.5m Calar Alto telescope. The spectra from each night were corrected for telluric absorption, sky emission lines, and stellar features, and were shifted to the planetary rest frame to search for the emission. Results. The He I emission is not detected in τ Boo b at a 5σ contrast limit of 4 × 10−4 for emission line widths of >20 km s−1. This is about a factor 8 above the expected emission level (assuming a typical He I transit absorption of 1% for hot Jupiters). This suggests that targeting the He I emission with well-designed observations using upcoming instruments such as VLT/CRIRES+ and E-ELT/HIRES is possible.

scholarly journals Probing the atmosphere of HD189733b with the Na i and K i lines

2020 ◽  
Vol 498 (1) ◽  
pp. 1023-1033
Author(s):  
E Keles ◽  
D Kitzmann ◽  
M Mallonn ◽  
X Alexoudi ◽  
L Fossati ◽  
...  
Keyword(s):  
High Resolution ◽  
High Altitude ◽  
Spectral Resolution ◽  
Absorption Lines ◽  
High Spectral Resolution ◽  
Transmission Spectra ◽  
Line Profiles ◽  
Line Broadening ◽  
Atmospheric Processes ◽  
Hot Jupiters

ABSTRACT High spectral resolution transmission spectroscopy is a powerful tool to characterize exoplanet atmospheres. Especially for hot Jupiters, this technique is highly relevant, due to their high-altitude absorption, e.g. from resonant sodium (Na i) and potassium (K i) lines. We resolve the atmospheric K i absorption on HD189733b with the aim to compare the resolved K i line and previously obtained high-resolution Na i-D line observations with synthetic transmission spectra. The line profiles suggest atmospheric processes leading to a line broadening of the order of ∼10 km/s for the Na i-D lines and only a few km/s for the K i line. The investigation hints that either the atmosphere of HD189733b lacks a significant amount of K i or the alkali lines probe different atmospheric regions with different temperature, which could explain the differences we see in the resolved absorption lines.

scholarly journals Detection of Fe i in the atmosphere of the ultra-hot Jupiter WASP-121b, and a new likelihood-based approach for Doppler-resolved spectroscopy

2020 ◽  
Vol 493 (2) ◽  
pp. 2215-2228 ◽  
Author(s):  
Neale P Gibson ◽  
Stephanie Merritt ◽  
Stevanus K Nugroho ◽  
Patricio E Cubillos ◽  
Ernst J W de Mooij ◽  
...  
Keyword(s):  
High Resolution ◽  
Temperature Inversion ◽  
Physical Parameters ◽  
Data Sets ◽  
Low Resolution ◽  
Additional Species ◽  
High Resolution Data ◽  
Higher Temperature ◽  
Multiple Species ◽  
Hot Jupiter

ABSTRACT High-resolution Doppler-resolved spectroscopy has opened up a new window into the atmospheres of both transiting and non-transiting exoplanets. Here, we present VLT/UVES observations of a transit of WASP-121b, an ‘ultra-hot’ Jupiter previously found to exhibit a temperature inversion and detections of multiple species at optical wavelengths. We present initial results using the blue arm of UVES (≈3700–5000 Å), recovering a clear signal of neutral Fe in the planet’s atmosphere at >8$\, \sigma$, which could contribute to (or even fully explain) the temperature inversion in the stratosphere. However, using standard cross-correlation methods, it is difficult to extract physical parameters such as temperature and abundances. Recent pioneering efforts have sought to develop likelihood ‘mappings’ that can be used to directly fit models to high-resolution data sets. We introduce a new framework that directly computes the likelihood of the model fit to the data, and can be used to explore the posterior distribution of parametrised model atmospheres via MCMC techniques. Our method also recovers the physical extent of the atmosphere, as well as account for time- and wavelength-dependent uncertainties. We measure a temperature of $3710^{+490}_{-510}$ K, indicating a higher temperature in the upper atmosphere when compared to low-resolution observations. We also show that the Fe i signal is physically separated from the exospheric Fe ii. However, the temperature measurements are highly degenerate with aerosol properties; detection of additional species, using more sophisticated atmospheric models, or combining these methods with low-resolution spectra should help break these degeneracies.

scholarly journals Phylotype-Level Characterization of Complex Lactobacilli Communities Using a High-Throughput, High-Resolution Phenylalanyl-tRNA Synthetase (pheS) Gene Amplicon Sequencing Approach

2020 ◽  
Author(s):  
Shaktheeshwari Silvaraju ◽  
Nandita Menon ◽  
Huan Fan ◽  
Kevin Lim ◽  
Sandra Kittelmann
Keyword(s):  
High Resolution ◽  
Amplicon Sequencing ◽  
Trna Synthetase ◽  
Species Level ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Low Resolution ◽  
Shotgun Metagenomics ◽  
Wide Range

ABSTRACTThe ‘lactobacilli’ to date encompass more than 270 closely related species that were recently re-classified into 26 genera. Because of their relevance to industry, there is a need to distinguish between closely related, yet metabolically and regulatory distinct species, e.g., during monitoring of biotechnological processes or screening of samples of unknown composition. Current available methods, such as shotgun metagenomics or rRNA-based amplicon sequencing have significant limitations (high cost, low resolution, etc.). Here, we generated a lactobacilli phylogeny based on phenylalanyl-tRNA synthetase (pheS) genes and, from it, developed a high-resolution taxonomic framework which allows for comprehensive and confident characterization of lactobacilli community diversity and structure at the species-level. This framework is based on a total of 445 pheS gene sequences, including sequences of 277 validly described species and subspecies (out of a total of 283, coverage of 98%). It allows differentiation between 263 lactobacilli species-level clades out of a total of 273 validly described species (including the proposed species L. timonensis) and a further two subspecies. The methodology was validated through next-generation sequencing of mock communities. At a sequencing depth of ∼30,000 sequences, the minimum level of detection was approximately 0.02 pg per μl DNA (equalling approximately 10 genome copies per µl template DNA). The pheS approach along with parallel sequencing of partial 16S rRNA genes revealed a considerable lactobacilli diversity and distinct community structures across a broad range of samples from different environmental niches. This novel complementary approach may be applicable to industry and academia alike.IMPORTANCESpecies within the former genera Lactobacillus and Pediococcus have been studied extensively at the genomic level. To accommodate for their exceptional functional diversity, the over 270 species were recently re-classified into 26 distinct genera. Despite their relevance to both academia and industry, methods that allow detailed exploration of their ecology are still limited by low resolution, high cost or copy number variations. The approach described here makes use of a single copy marker gene which outperforms other markers with regards to species-level resolution and availability of reference sequences (98% coverage). The tool was validated against a mock community and used to address lactobacilli diversity and community structure in various environmental matrices. Such analyses can now be performed at broader scale to assess and monitor lactobacilli community assembly, structure and function at the species (in some cases even at sub-species) level across a wide range of academic and commercial applications.

scholarly journals Phylotype-Level Characterization of Complex Communities of Lactobacilli Using a High-Throughput, High-Resolution Phenylalanyl-tRNA Synthetase (pheS) Gene Amplicon Sequencing Approach

2020 ◽  
Vol 87 (1) ◽  
Author(s):  
Shaktheeshwari Silvaraju ◽  
Nandita Menon ◽  
Huan Fan ◽  
Kevin Lim ◽  
Sandra Kittelmann
Keyword(s):  
High Resolution ◽  
Amplicon Sequencing ◽  
Trna Synthetase ◽  
Species Level ◽  
16S Rrna Genes ◽  
Rrna Genes ◽  
Low Resolution ◽  
Shotgun Metagenomics ◽  
Wide Range

ABSTRACT The lactobacilli identified to date encompass more than 270 closely related species that were recently reclassified into 26 genera. Because of their relevance to industry, there is a need to distinguish between closely related and yet metabolically and regulatory distinct species, e.g., during monitoring of biotechnological processes or screening of samples of unknown composition. Current available methods, such as shotgun metagenomics or rRNA gene-based amplicon sequencing, have significant limitations (high cost, low resolution, etc.). Here, we generated a phylogeny of lactobacilli based on phenylalanyl-tRNA synthetase (pheS) genes and, from it, developed a high-resolution taxonomic framework which allows for comprehensive and confident characterization of the community diversity and structure of lactobacilli at the species level. This framework is based on a total of 445 pheS gene sequences, including sequences of 276 validly described species and subspecies (of a total of 282, including the proposed L. timonensis species and the reproposed L. zeae species; coverage of 98%), and allows differentiation between 265 species-level clades of lactobacilli and the subspecies of L. sakei. The methodology was validated through next-generation sequencing of mock communities. At a sequencing depth of ∼30,000 sequences, the minimum level of detection was approximately 0.02 pg per μl DNA (equaling approximately 10 genome copies per μl template DNA). The pheS approach, along with parallel sequencing of partial 16S rRNA genes, revealed considerable diversity of lactobacilli and distinct community structures across a broad range of samples from different environmental niches. This novel complementary approach may be applicable to industry and academia alike. IMPORTANCE Species formerly classified within the genera Lactobacillus and Pediococcus have been studied extensively at the genomic level. To accommodate their exceptional functional diversity, the over 270 species were recently reclassified into 26 distinct genera. Despite their relevance to both academia and industry, methods that allow detailed exploration of their ecology are still limited by low resolution, high cost, or copy number variations. The approach described here makes use of a single-copy marker gene which outperforms other markers with regard to species-level resolution and availability of reference sequences (98% coverage). The tool was validated against a mock community and used to address diversity of lactobacilli and community structure in various environmental matrices. Such analyses can now be performed at a broader scale to assess and monitor the assembly, structure, and function of communities of lactobacilli at the species level (and, in some cases, even at the subspecies level) across a wide range of academic and commercial applications.

scholarly journals Main spectral features of meteors studied using a terawatt-class high-power laser

2019 ◽  
Vol 630 ◽  
pp. A127 ◽  
Author(s):  
M. Ferus ◽  
P. Kubelík ◽  
L. Petera ◽  
L. Lenža ◽  
J. Koukal ◽  
...  
Keyword(s):  
Experimental Data ◽  
Spectral Analysis ◽  
High Resolution ◽  
High Power ◽  
Laser System ◽  
Emission Spectra ◽  
Spectral Lines ◽  
Spectral Features ◽  
Low Resolution ◽  
Meteor Plasma

Context. Meteor spectra are commonly interpreted using data from databases and tables. Several studies have demonstrated very sophisticated calculations of elemental compositions of meteoroid bodies based on the computation of synthetic meteor spectra or on the spectral analysis of airglow plasma containing evaporated, atomized, and ionized meteoroid matter. However, considering accuracy, reliability of computations, lack of laboratory experimental data in this field, as well as the complicated physical structure of meteor plasma, such qualitative assignment or quantitative calculations are still extensively discussed in the scientific community. Even on the laboratory level, many studies have shown the high complexity of the acquisition and interpretation of the data that are recorded with techniques of emission spectroscopy that are in fashion and philosophy similar to the spectral analysis of meteor plasma, that is, detection and quantification of the elements that are ablated from complicated multicomponent matrices. Aims. The current study is focused on the application of terawatt-class laser-induced breakdown spectroscopy (TC-LIBS) of real samples of chondritic meteorites. We recorded emission spectra with high resolution and high precision that contain spectral lines that are typical for real meteoric spectra. Experimental data were compiled in a form that is convenient for the meteoric spectra interpretation and calibration. Methods. TC-LIBS was carried out by a high-power terawatt-class laser facility, the Prague Asterix Laser System (PALS). The spectra were simultaneously recorded by an echelle high-resolution spectrograph in the UV/VIS spectral ranges and by a low-resolution spectrograph that was used for real observation of meteor spectra. We also present calculated synthetic spectra based on data from the NIST atomic spectra database. Results. We assembled etalon qualitative tables of major meteoric spectral features that can be used both for the spectral wavelength calibration of low-resolution observational instruments and for the exact interpretation of meteor spectra. The data are compared with real meteor spectra.

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