We constrain the planetary atmospheric mass fraction at the time of the dispersal of the protoplanetary disk and the evolution of the stellar rotation rate for a dozen multi-planet systems that host ...sub-Neptunes and/or super-Earths. We employ a custom-developed Python code that we have dubbed Pasta (Planetary Atmospheres and Stellar roTation rAtes), which runs within a Bayesian framework to model the atmospheric evolution of exoplanets. The code combines MESA stellar evolutionary tracks, a model describing planetary structures, a model relating stellar rotation and activity level, and a model predicting planetary atmospheric mass-loss rates based on the results of hydrodynamic simulations. Through a MCMC scheme, we retrieved the posterior PDFs of all considered parameters. For ages older than about 2 Gyr, we find a median spin-down (i.e. \(P(t)\propto t^y\)) of \(\bar{y}=0.38_{-0.27}^{+0.38}\), indicating a rotation decay slightly slower than classical literature values (\(\approx\)0.5), though still within \(1\sigma\). At younger ages, we find a median spin-down (i.e. \(P(t)\propto t^x\)) of \(\bar{x}=0.26_{-0.19}^{+0.42}\), which is below what is observed in young open clusters, though within \(1\sigma\). However, these two results are likely due to a selection bias as the systems suitable to be analysed by Pasta contain at least one planet with a hydrogen-dominated atmosphere, implying that the host star has more likely evolved as a slow rotator. We further look for correlations between the initial atmospheric mass fraction of the considered planets and system parameters, but without finding any. The TESS, CHEOPS, and PLATO missions are going to be instrumental in identifying and precisely measuring systems amenable to Pasta's analysis and can thus potentially constrain planet formation and stellar evolution.
WASP-18 hosts a massive, very close-in Jupiter-like planet. Despite its young age (<1 Gyr), the star presents an anomalously low stellar activity level: the measured activity parameter lies slightly ...below the basal level; there is no significant time-variability in the value; there is no detection of the star in the X-rays. We present results of far-UV observations of WASP-18 obtained with COS on board of Hubble Space Telescope aimed at explaining this anomaly. From the star's spectral energy distribution, we infer the extinction ( 0.01 mag) and then the interstellar medium (ISM) column density for a number of ions, concluding that ISM absorption is not the origin of the anomaly. We measure the flux of the four stellar emission features detected in the COS spectrum (C ii, C iii, C iv, Si iv). Comparing the C ii/C iv flux ratio measured for WASP-18 with that derived from spectra of nearby stars with known age, we see that the far-UV spectrum of WASP-18 resembles that of old (>5 Gyr), inactive stars, in stark contrast with its young age. We conclude that WASP-18 has an intrinsically low activity level, possibly caused by star-planet tidal interaction, as suggested by previous studies. Re-scaling the solar irradiance reference spectrum to match the flux of the Si iv line, yields an XUV integrated flux at the planet orbit of 10.2 erg s−1 cm−2. We employ the rescaled XUV solar fluxes to models of the planetary upper atmosphere, deriving an extremely low thermal mass-loss rate of 10−20 MJ Gyr−1. For such high-mass planets, thermal escape is not energy limited, but driven by Jeans escape.
We aim to determine the fundamental properties of the \(\sim\)35 Myr old star TOI-837 and its close-in Saturn-sized planet, and to investigate the system's formation and evolutionary history. We ...analysed TESS photometry and HARPS spectroscopic data, measured stellar and planetary parameters, and characterised the stellar activity. We performed population synthesis simulations to track the formation history of TOI-837 \(b\), and to reconstruct its possible internal structure. We investigated the planetary atmospheric evolution through photo-evaporation, and quantified the prospects for atmospheric characterisation with JWST. TOI-837 \(b\) has radius and mass similar to those of Saturn (\(r_b\)=9.71\(^{+0.93}_{-0.60}\) \rearth, \(m_b\)=116\(^{+17}_{-18}\) M\(_\odot\), and \(\rho_b\)=0.68\(^{+0.20}_{-0.18}\) gcm\(^{-3}\)), on a primordial circular orbit. Population synthesis and early migration simulations suggest that the planet could have originated between 2-4 au, and have either a large and massive core, or a smaller Saturn-like core, depending on the opacity of the protoplanetary gas and on the growth rate of the core. We found that photo-evaporation produced negligible effects even at early ages (3-10 Myr). Transmission spectroscopy with JWST is very promising, and expected to provide constraints on atmospheric metallicity, abundance of H\(_2\)O, CO\(_2\), CH\(_4\) molecules, and to probe the presence of refractory elements. TOI-837 offers valuable prospects for follow-up observations, which are needed for a thorough characterisation. JWST will help to better constraining the formation and evolution history of the system, and understand whether TOI-837 \(b\) is a Saturn-analogue.
The research presents an analysis of the food security policy effectiveness on the component of food availability and access in two developing countries, Colombia and Kyrgyzstan, during the period ...from 2000 to 2018. Determining the state of their food balance trade and the regression analysis for the Food Production Index of the countries, considering four economic indicators. Thus the study attempts to show that policies and strategies have not reached the expected results in terms of reduction of food imports dependency and strengthening of national production and export industry. Furthermore was found that among the economic indicators considered, food inflation, food imports, food exports, and extreme monetary poverty; the last one was the indicator that presented influence on the Food Production Index of both countries, during the period analyzed, showing that access was the main component that defines the food production. The results highlighted the need of integrating food security with the monetary and trade policies of these countries.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
The atmospheric characterisation of hot and warm Neptune-size exoplanets is challenging due to their small radius and atmospheric scale height. The warm-Neptune HAT-P-11b is a remarkable target for ...such characterisation due to the large brightness of its host star (V=9.46 mag; H=7.13 mag). The aims of this work are to review the main physical and architectural properties of the HAT-P-11 planetary system, and to probe the presence of 8 molecular species in the atmosphere of HAT-P-11b at high spectral resolution in the near-infrared. The planetary system was reviewed by analysing transits and occultations of HAT-P-11b from the Kepler data set as well as HIRES at Keck archival radial-velocity (RV) data. We modelled the latter with Gaussian-process regression and a combined quasi-periodic and squared-exponential kernel to account for stellar variations on both (short-term) rotation and (long-term) activity-cycle timescales. In order to probe the atmospheric composition of HAT-P-11b, we observed 4 transits of this target with GIANO-B at TNG. We find that the long-period (\(P\sim9.3\) years) RV signal previously attributed to planet HAT-P-11c is more likely due to the stellar magnetic activity cycle. Nonetheless, the Hipparcos-Gaia difference in the proper-motion anomaly suggests that an outer-bound companion might still exist. For HAT-P-11b, we measure a radius \(R_{\rm p}=0.4466\pm0.0059\,R_{\rm J}\), a mass \(M_{\rm p}=0.0787\pm0.0048\,M_{\rm J}\), and an eccentricity \(e=0.2577^{+0.0033}_{-0.0025}\), in accordance with values in the literature. Probing its atmosphere, we detect \(NH_3\) (S/N\(=5.3\), significance\(=5.0\sigma\)) and confirm the presence of \(H_2O\) (S/N\(=5.1\), significance\(=3.4\sigma\)). We also tentatively detect the signal of \(CO_2\) (S/N\(=3.0\), significance\(=3.2\sigma\)) and \(CH_4\) (S/N\(=4.8\), significance\(=2.6\sigma\)), whose presence need to be confirmed by further observations.
Several results indicate that the atmospheric temperature of the ultra-hot Jupiter KELT-9b in the main line formation region is a few thousand degrees higher than predicted by self-consistent models. ...We test whether non-local thermodynamic equilibrium (NLTE) effects are responsible for the presumably higher temperature. We employ the Cloudy NLTE radiative transfer code to self-consistently compute the upper atmospheric temperature-pressure (TP) profile of KELT-9b, assuming solar metallicity. The Cloudy NLTE TP profile is \(\approx\)2000 K hotter than that obtained with previous models assuming local thermodynamic equilibrium (LTE). In particular, in the 1-10\(^{-7}\) bar range the temperature increases from \(\approx\)4000 K to \(\approx\)8500 K, remaining roughly constant at lower pressures. We find that the high temperature in the upper atmosphere of KELT-9b is driven principally by NLTE effects modifying the Fe and Mg level populations, which strongly influence the atmospheric thermal balance. We employ Cloudy to compute LTE and NLTE synthetic transmission spectra on the basis of the TP profiles computed in LTE and NLTE, respectively, finding that the NLTE model generally produces stronger absorption lines than the LTE model (up to 30%), which is largest in the ultraviolet. We compare the NLTE synthetic transmission spectrum with the observed H\(\alpha\) and H\(\beta\) line profiles obtaining an excellent match, thus supporting our results. The NLTE synthetic transmission spectrum can be used to guide future observations aiming at detecting features in the planet's transmission spectrum. Metals, such as Mg and Fe, and NLTE effects shape the upper atmospheric temperature structure of KELT-9b and thus affect the mass-loss rates derived from it. Finally, our results call for checking whether this is the case also of cooler planets.
The properties of the Hamaca of asphaltenes extra-heavy crude oil (AsfH) of Petroliferous Orinoco Belt can be modified for evaluating the changes produced with hydrotreating (HDT). One characterized ...the solid modified by means of UV-visible spectroscopy and nuclear magnetic proton resonance (NMR
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H). The samples were put under hydrotreating to 200°C to avoid thermal cracking, atmospheric pressure, and a flow of feeding of 10.5 mL/hr in a fixed-bed reactor in the presence of H
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S generated in situ. The reactivity was followed by gas chromatography (GC). All the samples were evaluated before and after being hydrotreated by
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H NMR, total sulfur analysis, and determination of molecular weight average by vapor pressure osmometry (VPO). The obtained results suggest the iron possibly is inserted in the structure of the asphaltene forming a new active phase catalytically, presumably a mixed sulfide (pyrrotite type) of iron-metal of transition (V and Ni) present in the asphaltene.
Transit-spectroscopy of exoplanets is one of the key observational techniques used to characterize extrasolar planets and their atmospheres. The observational challenges of these measurements require ...dedicated instrumentation and only the space environment allows undisturbed access to earth-like atmospheric features such as water or carbon dioxide. Therefore, several exoplanet-specific space missions are currently being studied. One of them is EChO, the Exoplanet Characterization Observatory, which is part of ESA's Cosmic Vision 2015–2025 program, and which is one of four candidates for the M3 launch slot in 2024.
In this paper we present the results of our assessment study of the EChO spectrometer, the only science instrument onboard this spacecraft. The instrument is a multi-channel all-reflective dispersive spectrometer, covering the wavelength range from 400 nm to 16μm simultaneously with a moderately low spectral resolution. We illustrate how the key technical challenge of the EChO mission — the high photometric stability — influences the choice of spectrometer concept and fundamentally drives the instrument design. First performance evaluations underline the suitability of the elaborated design solution for the needs of the EChO mission.
The field of exo-atmospheric characterisation is progressing at an extraordinary pace. Atmospheric observations are now available for tens of exoplanets, mainly hot and warm inflated gas giants, and ...new molecular species continue to be detected revealing a richer atmospheric composition than previously expected. Thanks to its warm equilibrium temperature (963\(\pm\)18~K) and low-density (0.219\(\pm\)0.031~g cm\(^{-3}\)), the close-in gas giant WASP-69b represents a golden target for atmospheric characterization. With the aim of searching for molecules in the atmosphere of WASP-69b and investigating its properties, we performed high-resolution transmission spectroscopy with the GIANO-B near-infrared spectrograph at the Telescopio Nazionale Galileo. We observed three transit events of WASP-69b. During a transit, the planetary lines are Doppler-shifted due to the large change in the planet's radial velocity, allowing us to separate the planetary signal from the quasi-stationary telluric and stellar spectrum. Considering the three nights together, we report the detection of CH\(_4\), NH\(_3\), CO, C\(_2\)H\(_2\), and H\(_2\)O, at more than \(3.3\sigma\) level. We did not identify the presence of HCN and CO\(_2\) with confidence level higher than 3\(\sigma\). This is the first time that five molecules are simultaneously detected in the atmosphere of a warm giant planet. These results suggest that the atmosphere of WASP-69b is possibly carbon-rich and characterised by the presence of disequilibrium chemistry.
The phenomenon of the organizational violence is extent and complex; this is due to the multiplicity of factors and of elements of individual, economic, social and political order that there take ...place. This work approaches initially the problem of the violence in general then to try to specify the problem of the work violence. Today this one is a wide field of investigation nevertheless in Colombia even it remains to do efforts to understand this phenomenon in an environment of political and social violence, in the frame of which rapid transformations are happening in the forms of organization of the work. Our method of work this one based on the accomplishment of semi-structured interviews with workers who have experienced some form of violence in the work. The analysis allows identifying some of the precursor agents of violence in the organizations and the manifestation forms of these have inside of the organizations.
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