Hot Atmosphere Research Articles

Silicon as a component of ferric oxide scale covering ductile iron pipes after annealing

All ductile iron pipe producers use the annealing process to improve the metal structure. It lasts several hours in a hot air atmosphere, when the surface of pipes is covered by ferric oxide scale, consisting usually of two significantly different layers, being the subject of the research reported here. In the U.S.A., commercially produced pipes are not protected by zinc coatings, because it is believed that ferric oxides are not a solid undercoat for such coatings, while the EN 545:2010 standard used in Europe requires the use of zinc or zinc-aluminum coatings, depending on soil corrosivity. To evaluate which approach has more potential, it is necessary first of all to recognize the structure of ferric oxides after the annealing process and then to understand their role as a base for zinc coatings. The microstructure of oxide scales grown on the external surface of industrial ductile iron pipes was investigated using scanning electron microscopy. In the ductile iron matrix, the concentration of silicon is reported to be much lower than in the layer of oxide scale growing directly on the pipe surface. In several samples, some cracks between the oxide layers were not successfully avoided in spite of using a professional saw with a continuous cooling process. Each time the cracks were horizontal and occurred along two boundaries: between the ductile iron matrix and the first oxide layer or between the two oxide layers rich in silicon and essentially silicon free.

In the Trenches of the Solar–Stellar Connection. III. The HST/COS Ecliptic-poles Stellar Survey (EclipSS)

Abstract The Ecliptic-poles Stellar Survey (EclipSS) collected far-ultraviolet (FUV: 1160–1420 Å) spectra of 49 nearby (d ≲ 100 pc) F3–K3 main-sequence stars, located at high ecliptic latitudes (north and south), using the Cosmic Origins Spectrograph of the Hubble Space Telescope. The ecliptic poles receive higher exposures from scanning missions like the Transiting Exoplanet Survey Satellite (high-precision optical photometry) and Extended Roentgen Survey with an Imaging Telescope Array (X-ray monitoring), which can deliver crucial contextual information, not otherwise easily secured. The objective was to support theoretical studies of stellar hot outer atmospheres—chromospheres (∼104 K) and coronae (≳1 MK)—which, among other things, can adversely impact exoplanets via host-star “space weather.” Flux–flux diagrams (e.g., C ii 1335 Å versus O i 1306 Å) were constructed for the EclipSS stars, solar Cycle 23/24 irradiances, and long-term FUV records of α Cen A (G2 V) and B (K1 V). The EclipSS cohort displays similar minimum (“basal”) fluxes to the Sun and solar twin α Cen A, in chromospheric O i 1306 Å. In hotter C ii 1335 Å, a downward slump of the basal fluxes—noted in previous, less controlled surveys—can now be explained as an effect of subsolar abundances. The consistent basal minima in chromospheric and higher temperature species at solar metallicity favor the idea that stellar analogs of the solar supergranulation network provide a baseline of high-energy emissions. The magnetic network is replenished by a “local dynamo” independently of the stellar spin. It can operate even when the starspot-spawning internal dynamo has ceased cycling, as during the Sun’s 17th century Maunder Minimum.

How planets grow by pebble accretion

During their formation, planets form large, hot atmospheres due to the ongoing accretion of solids. It has been customary to assume that all solids end up at the center, constituting a “core” of refractory materials, whereas the envelope remains metal-free. However, recent work, as well as observations by the Juno mission, indicate that the distinction may not be so clear cut. Indeed, small silicate, pebble-sized particles will sublimate in the atmosphere when they hit the sublimation temperature (T ~ 2000 K). In this paper we extend previous analytical work to compute the properties of planets within such a pebble accretion scenario. We conduct 1D numerical calculations of the atmosphere of an accreting planet, solving the stellar structure equations, augmented by a nonideal equation of state that describes a hydrogen and helium-silicate vapor mixture. Calculations terminate at the point where the total mass in metal is equal to that of the H+He gas, which we numerically confirm as the onset of runaway gas accretion. When pebbles sublimate before reaching the core, insufficient (accretion) energy is available to mix dense, vapor-rich lower layers with the higher layers of lower metallicity. A gradual structure in which Z decreases with radius is therefore a natural outcome of planet formation by pebble accretion. We highlight, furthermore, that (small) pebbles can act as the dominant source of opacity, preventing rapid cooling and presenting a channel for (mini-)Neptunes to survive in gas-rich disks. Nevertheless, once pebble accretion subsides, the atmosphere rapidly clears followed by runaway gas accretion. We consider atmospheric recycling to be the most probable mechanism to have stalled the growth of the envelopes of these planets.

Analisis Terciptanya Transisi Kepemimpinan Baru Dalam Perhelatan Pilkada Ponorogo Dilihat Dari Perspektif Masyarakat

The implementation of the Ponorogo regional election in 2020 is indeed in a special atmosphere, considering that two competitor pairs of candidates are fighting for people’s sympathies in order to grab seat number 1 in Ponorogo. In welcoming the people’s democratic party, the hot atmosphere is identical to be found in the field. Regional election is a prestigious event to determine the fate of the region for the next 5 years, so that all parties are competing to give their best. In Ponorogo, both of successful team and volunteers from both pairs of candidates showed enthusiasm and support in many ways interestingly, the competition in the Ponorogo regional election was between two old competitors namely Sugiri Sancoko VS Ipong Muchlissoni where in the previous regional election (2015) had heated up to a dispute over the election results. A new chapter has begun, but the atmosphere of competition is certainly more heated for both sides. The leadership note of the regent of Ipong Muhclissoni is a major highlight, which has been felt by the people of Ponorogo through experience and understanding over the past 5 years. This researches aims to narrow the perspective of society, so that it provides a concrete picture of two possibilities, namely: the emergence of a new leader, or retaining an old leader. Because officially in the Ponorogo regional election in 2020 there are only two candidates, it is very interesting to conduct this research.         Keywords : Transition, Leadership, Regional Election

Experimental study and analytical analysis on the global heat transfer of stratified corium in LWR lower head

In-Vessel Melt Retention (IVR) is credited as a promising Severe Accident Management strategy to stabilize the molten corium during severe accident scenarios. This strategy is not only adopted in VVER 440 or AP600 designs, but is also included in higher power reactors around 1000 MWe, such as AP1000 and Chinese CPR 1000. One of the current research priorities bound with large uncertainty is the heat flux at the cooled wall in the metallic layer atop of a ceramic pool, as heat flux focusing effect could appear at this location. The generation of experimental data with naturally separated melt layers is essential to improve the understanding of the heat transfer between the melt layers and on their boundaries. Under the framework of EU H2020 IVMR project, two large-scale test series with simulant materials were conducted in LIVE2D facility at KIT. Rigid top cooling and hot atmosphere on the upper layer were realized in a two-layer melt pool with different upper layer thicknesses. Important global heat transfer phenomena have been obtained, including the effect of the top cooling boundary, the behaviour of the interlayer crust and the impact of upper layer thickness. Finally, the influence of Pr number and geometry are discussed.

Correlations between supermassive black holes and hot gas atmospheres in IllustrisTNG and X-ray observations

ABSTRACT Recent X-ray observations have revealed remarkable correlations between the masses of central supermassive black holes (SMBHs) and the X-ray properties of the hot atmospheres permeating their host galaxies, thereby indicating the crucial role of the atmospheric gas in tracing SMBH growth in the high-mass regime. We examine this topic theoretically using the IllustrisTNG cosmological simulations and provide insights to the nature of this SMBH – gaseous halo connection. By carrying out a mock X-ray analysis for a mass-selected sample of TNG100 simulated galaxies at $z$ = 0, we inspect the relationship between the masses of SMBHs and the hot gas temperatures and luminosities at various spatial and halo scales – from galactic (∼Re) to group/cluster scales (∼R500c). We find strong SMBH-X-ray correlations mostly in quenched galaxies and find that the correlations become stronger and tighter at larger radii. Critically, the X-ray temperature (kBTX) at large radii (r ≳ 5Re) traces the SMBH mass with a remarkably small scatter (∼0.2 dex). The relations emerging from IllustrisTNG are broadly consistent with those obtained from recent X-ray observations. Overall, our analysis suggests that, within the framework of IllustrisTNG, the present-time MBH–kBTX correlations at the high-mass end (MBH ≳ 108M⊙) are fundamentally a reflection of the SMBH mass–halo mass relation, which at such high masses is set by the hierarchical assembly of structures. The exact form, locus, and scatter of those scaling relations are, however, sensitive to feedback processes such as those driven by star formation and SMBH activity.

An active source seismo-acoustic experiment using tethered balloons to validate instrument concepts and modelling tools for atmospheric seismology

SUMMARYThe measurements of acoustic waves created by a quake are of great interest for planets with hot and dense atmospheres, like Venus, because surface deployments of seismometers will last only a few hours, whereas freeflying balloons could fly many days. Infrasound sensors can also be used to constrain subsurface properties during active seismic experiments. This study presents a controlled source seismo-acoustic experiment using infrasonic sensors and accelerometers mounted on a tethered helium balloon. Both the acoustic waves generated below the balloon by seismic surface waves, and the ones generated by strong ground motions above the seismic source are clearly observed and separated on the records of the various instruments. This data set allows various validations and investigations. First, it validates the ground to air coupling theory and our numerical modelling tools. Then, it allows us to demonstrate that antenna processing of infrasound sensors deployed below the balloon can estimate the arrival incidence angle of the acoustic waves within 10°. Finally, a polarization analysis of the accelerometers taped on the balloon envelope is presented. It demonstrates that accelerometer records are strongly dependent on their location on the balloon due to its deformations and rotations. However, the different acoustic signals can be distinguished through their polarization, and a best sensor location is estimated at the bottom of the balloon envelope. These results are a first step towards detecting and locating seismic activity using airborne acoustic sensors on Venus and elsewhere. However, some observations of earthquake signals in a more realistic geometry are still missing.

Numerical analysis of the autoignition of isolated wet ethanol droplets immersed in a hot and humid air atmosphere

Results of time-dependent, spherically symmetrical computations of the vaporization and combustion of ethanol and ethanol/water droplets are reported. Mixture-average transport was employed, along with a systematically reduced chemical-kinetic mechanism involving 15 overall steps among 17 chemical species, to speed the computations by a factor of about 100 over what would be required if full detailed chemistry had been used. Absorption of water from the gas surrounding the droplet and its diffusive transport within the liquid phase were taken into account, providing excellent agreement with previous experimental and computational results for the combustion of ethanol droplets in air. On the other hand, the assumption of rapid liquid-phase mixing produced very poor agreement when water condensation on the droplet surface or hydrous ethanol are considered. To characterize autoignition, we define the critical autoignition temperature T ∞ c as the critical ambient temperature below which autoignition is not observed. Computations for autoignition of cold ethanol/water droplets in air showed that T ∞ c decreases with increasing initial droplet diameters. In the range of parameters under consideration, ignition was found to take place always before complete vaporization of the droplet, and the ignition time was found to become longer with the increasing initial water content of the liquid ethanol droplet. On the contrary, addition of water vapor to the initial air atmosphere was found to shorten the ignition time, increasing ethanol vaporization rate as a consequence of the extra heat release associated with water absorption into the liquid.

Hydrodynamical simulations of protoplanetary disks including irradiation of stellar photons

Context. In recent years hydrodynamical (HD) models have become important to describe the gas kinematics in protoplanetary disks, especially in combination with models of photoevaporation and/or magnetically driven winds. Our aim is to investigate how vertical shear instability (VSI) could influence the thermally driven winds on the surface of protoplanetary disks. Aims. In this first part of the project, we focus on diagnosing the conditions of the VSI at the highest numerical resolution ever recorded, and suggest at what resolution per scale height we obtain convergence. At the same time, we want to investigate the vertical extent of VSI activity. Finally, we determine the regions where extreme UV (EUV), far-UV (FUV), and X-ray photons are dominant in the disk. Methods. We perform global HD simulations using the PLUTO code. We adopt a global isothermal accretion disk setup, 2.5D (2 dimensions, 3 components) which covers a radial domain from 0.5 to 5.0 and an approximately full meridional extension. Our simulation runs cover a resolution from 12 to 203 cells per scale height. Results. We determine 50 cells per scale height to be the lower limit to resolve the VSI. For higher resolutions, ≥50 cells per scale height, we observe the convergence for the saturation level of the kinetic energy. We are also able to identify the growth of the “body” modes, with higher growth rate for higher resolution. Full energy saturation and a turbulent steady state is reached after 70 local orbits. We determine the location of the EUV heated region defined by Σr = 1019 cm−2 to be at HR ~ 9.7 and the FUV–X-ray heated boundary layer defined by Σr = 1022 cm−2 to be at HR ~ 6.2, making it necessary to introduce a hot atmosphere. For the first time we report the presence of small-scale vortices in the r − Z plane between the characteristic layers of large-scale vertical velocity motions. Such vortices could lead to dust concentration, promoting grain growth. Our results highlight the importance of combining photoevaporation processes in the future high-resolution studies of turbulence and accretion processes in disks.

Temperature inversions on hot super-Earths: the case of CN in nitrogen-rich atmospheres

ABSTRACT We show that in extremely irradiated atmospheres of hot super-Earths shortwave absorption of CN can cause strong temperature inversions. We base this study on previous observations of 55 Cancri e, which lead us to believe that ultrashort-period super-Earths can sustain volatile atmospheres, rich in nitrogen and/or carbon. We compute our model atmospheres in a radiative-convective equilibrium for a variety of nitrogen-rich cases and orbital parameters. We demonstrate the effects caused by thermal inversions on the chemistry and compute low-resolution synthetic emission spectra for a range of 0.5–28 $\rm{\mu m}$. Our results indicate that due to shortwave absorption of CN, atmospheres with temperatures above 2000 K and C/O ≥ 1.0 are prone to thermal inversions. CN is one of the few molecules that is extremely stable at large temperatures occurring on the dayside of short-period super-Earths. The emission spectrum of such atmospheres will differ substantially from non-inverted cases. In the case of inversions, absorption features become inverted, showing higher than expected flux. We propose that inversions in hot atmospheres should be the expected norm. Hot super-Earths are some of the most extreme natural laboratories for testing predictions of atmospheric chemistry and structure. They are frequently occurring, bright in emission and have short orbital periods. All these factors make them perfect candidates to be observed with JWST and ARIEL missions.

Search and analysis of giant radio galaxies with associated nuclei (SAGAN)

Radio galaxies with jets of relativistic particles are usually hosted by massive elliptical galaxies with active nuclei powered by accretion of interstellar matter onto a supermassive black hole. In some rare cases (< 5%), their jets drive the overall structure to sizes larger than 700 kpc, and they are called giant radio galaxies (GRGs). A very small fraction of the population of such radio galaxies contains molecular and atomic gas in the form of rings or discs that can fuel star formation. The origin of this gas is not well known; it has sometimes been associated with a minor merger with a gas-rich disc galaxy (e.g. Centaurus A) or cooling of material from a hot X-ray atmosphere (e.g. cooling flows). The giant radio jets might be the extreme evolution of these objects, and they can teach us about the radio galaxy evolution. We selected 12 targets from a catalogue of 820 GRGs that are likely to be in a gas-accretion and star formation phase. The targets were selected from the mid-infrared to contain heated dust. We report here the results of IRAM-30m observations, the molecular gas content, and the star formation efficiency, and we discuss the origin of the gas and disc morphology. Three out of our 12 targets are detected, and for the others, we report significant upper limits. We combine our three detections and upper limits with four additional detected GRGs from the literature to discuss the results. Most of the GRG targets belong to the main sequence, and a large fraction are in the passive domain. Their star formation efficiency is comparable to normal galaxies, except for two galaxies that are deficient in molecular gas with a short (∼200 Myr) depletion time, and a quiescent gas-rich giant spiral galaxy. In general, the depletion time is much longer than the lifetime of the giant radio jet.

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

WASP-127b is one of the puffiest exoplanets found to date, with a mass of only 3.4 Neptune masses, but a radius larger than that of Jupiter. It is located at the border of the Neptune desert, which describes the lack of highly irradiated Neptune-sized planets, and which remains poorly understood. Its large scale height and bright host star make the transiting WASP-127b a valuable target to characterise in transmission spectroscopy. We used combined EulerCam and TESS light curves to recalculate the system parameters. Additionally, we present an in-depth search for sodium in four transit observations of WASP-127b, obtained as part of the Hot Exoplanet Atmosphere Resolved with Transit Spectroscopy (HEARTS) survey with the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph. Two nights from this dataset were analysed independently by another team. The team claimed a detection of sodium that is incompatible with previous studies of data from both ground and space. We show that this strong sodium detection is due to contamination from telluric sodium emissions and the low signal-to-noise ratio in the core of the deep stellar sodium lines. When these effects are properly accounted for, the previous sodium signal is reduced to an absorption of 0.46 ± 0.20% (2.3σ), which is compatible with analyses of WASP-127b transits carried out with other instruments. We can fit a Gaussian to the D2 line, but the D1 line was not detected. This indicates an unusual line ratio if sodium exists in the atmosphere. Follow-up of WASP-127 at high resolution and with high sensitivity is required to firmly establish the presence of sodium and analyse its line shape.

Hot gaseous atmospheres of rotating galaxies observed with XMM–Newton

ABSTRACT X-ray emitting atmospheres of non-rotating early-type galaxies and their connection to central active galactic nuclei have been thoroughly studied over the years. However, in systems with significant angular momentum, processes of heating and cooling are likely to proceed differently. We present an analysis of the hot atmospheres of six lenticulars and a spiral galaxy to study the effects of angular momentum on the hot gas properties. We find an alignment between the hot gas and the stellar distribution, with the ellipticity of the X-ray emission generally lower than that of the optical stellar emission, consistent with theoretical predictions for rotationally supported hot atmospheres. The entropy profiles of NGC 4382 and the massive spiral galaxy NGC 1961 are significantly shallower than the entropy distribution in other galaxies, suggesting the presence of strong heating (via outflows or compressional) in the central regions of these systems. Finally, we investigate the thermal (in)stability of the hot atmospheres via criteria such as the TI- and C-ratio, and discuss the possibility that the discs of cold gas present in these objects have condensed out of the hot atmospheres.

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

Planet formation processes or evolution mechanisms are surmised to be at the origin of the hot Neptune desert. Studying exoplanets currently living within or at the edge of this desert could allow disentangling the respective roles of formation and evolution. We present the High Accuracy Radial velocity Planet Searcher (HARPS) transmission spectrum of the bloated super-Neptune WASP-166b, located at the outer rim of the Neptune desert. Neutral sodium is detected at the 3.4σ level (0.455 ± 0.135%), with a tentative indication of line broadening, which could be caused by winds blowing sodium farther into space, a possible manifestation of the bloated character of these highly irradiated worlds. We put this detection into context with previous work claiming a non-detection of sodium in the same observations and show that the high noise in the trace of the discarded stellar sodium lines was responsible for the non-detection. We highlight the impact of this low signal-to-noise ratio remnant on detections for exoplanets similar to WASP-166b.

Hot Exoplanet Atmospheres Resolved with Transit Spectroscopy (HEARTS)

Context.WASP-121 b is a hot Jupiter that was recently found to possess rich emission (day side) and transmission (limb) spectra, suggestive of the presence of a multitude of chemical species in the atmosphere.Aims.We survey the transmission spectrum of WASP-121 b for line-absorption by metals and molecules at high spectral resolution and elaborate on existing interpretations of the optical transmission spectrum observed with theHubbleSpace Telescope (HST).Methods.We applied the cross-correlation technique and direct differential spectroscopy to search for sodium and other neutral and ionised atoms, TiO, VO, and SH in high-resolution transit spectra obtained with the HARPS spectrograph. We injected models assuming chemical and hydrostatic equilibrium with a varying temperature and composition to enable model comparison, and employed two bootstrap methods to test the robustness of our detections.Results.We detect neutral Mg, Na, Ca, Cr, Fe, Ni, and V, which we predict exists in equilibrium with a significant quantity of VO, supporting earlier observations by HST/WFC3. Non-detections of Ti and TiO support the hypothesis that Ti is depleted via a cold-trap mechanism, as has been proposed in the literature. Atomic line depths are under-predicted by hydrostatic models by a factor of 1.5 to 8, confirming recent findings that the atmosphere is extended. We predict the existence of significant concentrations of gas-phase TiO2, VO2, and TiS, which could be important absorbers at optical and near-IR wavelengths in hot Jupiter atmospheres. However, accurate line-list data are not currently available for them. We find no evidence for absorption by SH and find that inflated atomic lines can plausibly explain the slope of the transmission spectrum observed in the near-ultraviolet with HST. The Na ID lines are significantly broadened (FWHM~50 to 70 km s−1) and show a difference in their respective depths of ~15 scale heights, which is not expected from isothermal hydrostatic theory. If this asymmetry is of astrophysical origin, it may indicate that Na Iforms an optically thin envelope, reminiscent of the Na Icloud surrounding Jupiter, or that it is hydrodynamically outflowing.

How Do Supernovae Impact the Circumgalactic Medium? I. Large-scale Fountains around a Milky Way–like Galaxy

Abstract Feedback is indispensable in galaxy formation. However, lacking resolutions, cosmological simulations often use ad hoc feedback parameters. Conversely, small-box simulations, while they better resolve the feedback, cannot capture gas evolution beyond the simulation domain. We aim to bridge the gap by implementing small-box results of supernovae-driven outflows into dark matter halo-scale simulations and studying their impact on large scales. Galactic outflows are multiphase, but small-box simulations show that the hot phase (T ≈ 106–7 K) carries the majority of energy and metals. We implement hot outflows in idealized simulations of the Milky Way halo, and examine how they impact the circumgalactic medium. In this paper, we discuss the case when the star formation surface density is low and therefore the emerging hot outflows are gravitationally bound by the halo. We find that outflows form a large-scale, metal-enriched atmosphere with fountain motions. As hot gas accumulates, the inner atmosphere becomes “saturated.” Cool gas condenses, with a rate balancing the injection of the hot outflows. This balance leads to a universal density profile of the hot atmosphere, independent of mass outflow rate. The atmosphere has a radially decreasing temperature, naturally producing the observed X-ray luminosity and column densities of O vi, O vii, and O viii. The self-regulated atmosphere has a baryon and a metal mass of (0.5–1.2) × 1010 M ⊙ and (0.6–1.4) × 108 M ⊙, respectively, small compared to the “missing” baryons and metals from the halo. We conjecture that the missing materials reside at even larger radii, ejected by more powerful outflows in the past.

Modulations of synoptic and climatic changes on ozone pollution and its health risks in mountain-basin areas

Abstract Ozone (O3) pollution in China tends to become increasingly severe despite recent emission reductions. O3 is sensitive to atmospheric conditions, but its modulations by changing synoptic systems and climate are unclear, especially in mountain-basin areas such as the Sichuan Basin (SCB). This study examines the impacts of typical synoptic systems and their secular changes on O3 pollution and its health risks in mountain-basin areas, by taking SCB as an example. Seven dominant synoptic patterns are identified and three typical synoptic patterns with high- (low-) pressure are associated with high (low) O3 concentrations over entire SCB, while the pattern with uniform-pressure is accompanied by heavy (light) pollution in western (eastern) SCB. Under the synoptic patterns with high-pressure, clear weather with fewer clouds, strong solar radiation, weak convection, and hot and dry atmosphere enhances the photochemical reactions of O3 precursors and weakens the vertical mixing of O3 and its precursors, thus favoring heavy O3 pollution and posing higher health risks; whereas, the synoptic patterns with low-pressure induce the opposite changes in O3 concentration and health risks. The uniform-pressure pattern is accompanied by district spatial variations of O3 via favoring O3-related physical and chemical processes in eastern SCB and inhibiting that in the west. Under climatic changes, increasing synoptic pattern with high-pressure and decreasing synoptic pattern with low-pressure over SCB significantly increased O3 concentration and the resultant health risks over the past 40 years. Our findings provide scientific evidence from synoptic and climatic views for forecasting O3 and its health risks and for mitigating O3 pollution in mountain-basin areas.

The 2020 release of the ExoMol database: Molecular line lists for exoplanet and other hot atmospheres

The ExoMol database (www.exomol.com) provides molecular data for spectroscopic studies of hot atmospheres. While the data are intended for studies of exoplanets and other astronomical bodies, the dataset is widely applicable. The basic form of the database is extensive line lists; these are supplemented with partition functions, state lifetimes, cooling functions, Landé g-factors, temperature-dependent cross sections, opacities, pressure broadening parameters, k-coefficients and dipoles. This paper presents the latest release of the database which has been expanded to consider 80 molecules and 190 isotopologues totaling over 700 billion transitions. While the spectroscopic data are concentrated at infrared and visible wavelengths, ultraviolet transitions are being increasingly considered in response to requests from observers. The core of the database comes from the ExoMol project which primarily uses theoretical methods, albeit usually fine-tuned to reproduce laboratory spectra, to generate very extensive line lists for studies of hot bodies. The data have recently been supplemented by line lists derived from direct laboratory observations, albeit usually with the use of ab initiotransition intensities. A major push in the new release is towards accurate characterisation of transition frequencies for use in high resolution studies of exoplanets and other bodies.

LOFAR observations of X-ray cavity systems

ABSTRACTWe present LOFAR observations at 120–168 MHz of 42 systems with possible X-ray cavities in their hot atmosphere, of which 17 are groups or ellipticals, 19 are nearby clusters (z < 0.3), and six are higher redshift clusters (z > 0.3). The X-ray cavities, formed by the radio lobes of the central active galactic nucleus (AGN), are evidence of radio-mode AGN feedback. In the groups and ellipticals sample, half of the systems have X-ray cavities for which no associated lobe emission was detected. Conversely, we report the discovery of large radio lobes in NGC 6338, extending far beyond the emission reported previously in the literature. In the case of the nearby clusters, our observations show that there is little low-frequency radio emission that extends beyond the cavities (e.g. MS 0735.6+7421, A2052). For the first time, we report secure cavity-radio associations in 2A 0335+096, ZwCl 2701, and ZwCl 8276 that strengthens their interpretation as AGN-created cavities. However, in some known cavity systems (e.g. A1795 and ZwCl 3146) we report the lack of detectable low-frequency radio emission associated with the cavities. Our sample of higher redshifts systems is small, and unfortunately the present LOFAR observations are not able to resolve the lobes in many of them. Nevertheless, our sample represents one of the best available for investigating the connection between radio and jet power in radio-mode AGN feedback.

A new set of atmosphere and evolution models for cool T–Y brown dwarfs and giant exoplanets

We present a new set of solar metallicity atmosphere and evolutionary models for very cool brown dwarfs and self-luminous giant exoplanets, which we term ATMO 2020. Atmosphere models are generated with our state-of-the-art 1D radiative-convective equilibrium code ATMO, and are used as surface boundary conditions to calculate the interior structure and evolution of 0.001–0.075 M⊙ objects. Our models include several key improvements to the input physics used in previous models available in the literature. Most notably, the use of a new H–He equation of state including ab initio quantum molecular dynamics calculations has raised the mass by ~1−2% at the stellar–substellar boundary and has altered the cooling tracks around the hydrogen and deuterium burning minimum masses. A second key improvement concerns updated molecular opacities in our atmosphere model ATMO, which now contains significantly more line transitions required to accurately capture the opacity in these hot atmospheres. This leads to warmer atmospheric temperature structures, further changing the cooling curves and predicted emission spectra of substellar objects. We present significant improvement for the treatment of the collisionally broadened potassium resonance doublet, and highlight the importance of these lines in shaping the red-optical and near-infrared spectrum of brown dwarfs. We generate three different grids of model simulations, one using equilibrium chemistry and two using non-equilibrium chemistry due to vertical mixing, all three computed self-consistently with the pressure-temperature structure of the atmosphere. We show the impact of vertical mixing on emission spectra and in colour-magnitude diagrams, highlighting how the 3.5−5.5 μm flux window can be used to calibrate vertical mixing in cool T–Y spectral type objects.