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Spectropolarimetic campaigns have established that large-scale magnetic fields are present at the surfaces of approximately 10% of massive dwarf stars. However, there is a dearth of magnetic field measurements for their deep interiors. Asteroseismology of gravity-mode pulsations combined with rotating magneto-hydrodynamical calculations of the early-B main-sequence star HD 43317 constrain its magnetic field strength to be approximately 5 × 105 G just outside its convective core. This proof-of-concept study for magneto-asteroseismology opens a new window into the observational characterisation of magnetic fields inside massive stars. [ABSTRACT FROM AUTHOR]

The ESA/KU Leuven CubeSpec mission is specifically designed to provide low-cost space-based high-resolution optical spectroscopy. Here we highlight the science requirements and capabilities of CubeSpec. The primary science goal is to perform pulsation mode identification from spectroscopic line profile variability and empower asteroseismology of massive stars. [ABSTRACT FROM AUTHOR]

A helium‐filled mylar balloon carrying a smartphone and infrasound sensors ascended to a stratospheric height of 35 km over the surface detonation of a chemical explosive, with a total acoustic propagation distance of 127 km. The smartphone was configured to collect multi‐modal data at high rates from internal sensors. Analysis of the data shows successful collection of the explosion signal by both the smartphone's microphone and its accelerometers, the first from an ascending balloon. Comparison of the acoustic signal with that collected by other infrasound sensors, both airborne and ground‐based, provides insight into the possibilities and limitations of collecting acoustic data from the stratosphere. Plain Language Summary: A surface chemical explosion was observed by pressure and acceleration sensors suspended from an ascending free‐floating balloon at a height of 35 km and a total propagation distance of 127 km from the blast. The balloon's sensor package included a smartphone collecting different types of data (including audio, acceleration, and position), as well as more traditional infrasound and location sensors. The explosion signal was observed by the airborne pressure and vertical accelerometer sensors, as well as by surface‐deployed traditional and smartphone pressure and acceleration sensors. The blast signatures recorded by the airborne and ground‐based stations are compared to provide insight into the present capabilities, limitations, and possible improvements to future balloon‐borne collections of seismo‐acoustic signatures on Earth and beyond. Key Points: Explosion signals were captured using acoustic sensors in an ascending balloon at a height of 35 km and a propagation distance of 127 kmThe signal was briefly trapped in the troposphere before escaping into the stratosphereAccelerometers can distinguish acoustic signals from wind noise on ascending balloons [ABSTRACT FROM AUTHOR]

The Sound Fixing and Ranging (SOFAR) channel in the ocean allows for low frequency sound to travel thousands of kilometers, making it particularly useful for detecting underwater nuclear explosions. Suggestions that an elevated SOFAR‐like channel should exist in the stratosphere date back over half a century and imply that sources within this region can be reliably sensed at vast distances. However, this theory has not been supported with evidence of direct observations from sound within this channel. Here we show that an infrasound sensor on a solar hot air balloon recorded the first infrasound detection of a ground truth airborne source while within this acoustic channel, which we refer to as the AtmoSOFAR channel. Our results support the existence of the AtmoSOFAR channel, demonstrate that acoustic signals can be recorded within it, and provide insight into the characteristics of recorded signals. Results also show a lack of detections on ground‐based stations, highlighting the advantages of using balloon‐borne infrasound sensors to detect impulsive sources at altitude. Plain Language Summary: A layer exists in the ocean that allows sound to travel great distances. Something like this could exist in our atmosphere, too, but until now no one had verified this. Low frequency sound, known as infrasound, travels efficiently through the atmosphere. Specialized instruments, called infrasound sensors, are microphones that can record low frequency sound. We attached an infrasound sensor to a solar hot air balloon to make the first recording of a known object within the theorized atmospheric layer. Our results show that this layer exists, sound can be recorded within it, and analysis can give us more information about what generated that sound. The rocket launch was not well recorded by infrasound sensors on the ground, highlighting the advantages of our method for detecting objects that travel through this region of the atmosphere. Key Points: First direct observation of an elevated acoustic duct using an airborne acoustic source and receiverDetections provide insight into the characteristics of signals from ascending and descending supersonic objectsLack of detections on ground‐based stations highlights the advantages of using balloon‐borne sensors to detect sources at altitude [ABSTRACT FROM AUTHOR]

We present the analysis of the optical variability of the early, nitrogen-rich Wolf–Rayet (WR) star WR 7. The analysis of multisector Transiting Exoplanet Survey Satellite (TESS) light curves and high-resolution spectroscopic observations confirm multiperiodic variability that is modulated on time-scales of years. We detect a dominant period of 2.6433 ± 0.0005 d in the TESS sectors 33 and 34 light curves in addition to the previously reported high-frequency features from sector 7. We discuss the plausible mechanisms that may be responsible for such variability in WR 7, including pulsations, binarity, co-rotating interaction regions (CIRs), and clumpy winds. Given the lack of strong evidence for the presence of a stellar or compact companion, we suggest that WR 7 may pulsate in quasi-coherent modes in addition to wind variability likely caused by CIRs on top of stochastic low-frequency variability. WR 7 is certainly a worthy target for future monitoring in both spectroscopy and photometry to sample both the short (≲1 d) and long (≳1000 d) variability time-scales. [ABSTRACT FROM AUTHOR]

Spectropolarimetic campaigns have established that large-scale magnetic fields are present at the surfaces of approximately 10% of massive dwarf stars. However, there is a dearth of magnetic field measurements for their deep interiors. Asteroseismology of gravity-mode pulsations combined with rotating magneto-hydrodynamical calculations of the early-B main-sequence star HD 43317 constrain its magnetic field strength to be approximately 5 × 105 G just outside its convective core. This proof-of-concept study for magneto-asteroseismology opens a new window into the observational characterisation of magnetic fields inside massive stars. [ABSTRACT FROM AUTHOR]

Among the intermediate mass pulsating stars known as δ Sct stars is a subset of high-amplitude and predominantly radial-mode pulsators known as high-amplitude δ Sct (HADS) stars. From more than 2000 δ Sct stars observed by the Kepler space mission, only two HADS stars were detected. We investigate the more perplexing of these two HADS stars, KIC 5950759. We study its variability using ground- and space-based photometry, determine its atmospheric parameters from spectroscopy and perform asteroseismic modelling to constrain its mass and evolutionary stage. From spectroscopy, we find that KIC 5950759 is a metal-poor star, which is in agreement with the inferred metallicity needed to reproduce its pulsation mode frequencies from non-adiabatic pulsation models. Furthermore, we combine ground-based WASP and Kepler space photometry, and measure a linear change in period of order |$\dot{P}/P \simeq 10^{-6}$|  yr−1 for both the fundamental and first overtone radial modes across a time base of several years, which is at least two orders of magnitude larger than predicted by evolution models, and is the largest measured period change in a δ Sct star to date. Our analysis indicates that KIC 5950759 is a metal-poor HADS star near the short-lived contraction phase and the terminal-age main sequence, with its sub-solar metallicity making it a candidate SX Phe star. KIC 5950759 is a unique object among the thousands of known δ Sct stars and warrants further study to ascertain why its pulsation modes are evolving remarkably faster than predicted by stellar evolution. [ABSTRACT FROM AUTHOR]

The ESA/KU Leuven CubeSpec mission is specifically designed to provide low-cost space-based high-resolution optical spectroscopy. Here we highlight the science requirements and capabilities of CubeSpec. The primary science goal is to perform pulsation mode identification from spectroscopic line profile variability and empower asteroseismology of massive stars. [ABSTRACT FROM AUTHOR]

We present an analysis of the high-mass eclipsing binary system VV Ori based on photometry from the TESS satellite. The primary star (B1 V, 9.5  |$\, {\rm M}_\odot$|⁠) shows β Cephei pulsations and the secondary (B7 V, 3.8  |$\, {\rm M}_\odot$|⁠) is possibly a slowly pulsating B star. We detect 51 significant oscillation frequencies, including two multiplets with separations equal to the orbital frequency, indicating that the pulsations are tidally perturbed. We analyse the TESS light curve and published radial velocities to determine the physical properties of the system. Both stars are only the second of their pulsation type with a precisely measured mass. The orbital inclination is also currently decreasing, likely due to gravitational interactions with a third body. [ABSTRACT FROM AUTHOR]

V453 Cyg is an eclipsing binary containing 14 and 11  |$\, {\rm M}_\odot$| stars in an eccentric short-period orbit. We have discovered β Cep-type pulsations in this system using Transiting Exoplanet Survey Satellite data. We identify seven significant pulsation frequencies, between 2.37 and 10.51 d−1, in the primary star. These include six frequencies that are separated by yet significantly offset from harmonics of the orbital frequency, indicating they are tidally perturbed modes. We have determined the physical properties of the system to high precision: V453 Cyg A is the first β Cep pulsator with a precise mass measurement. The system is a vital tracer of the physical processes that govern the evolution of massive single and binary stars. [ABSTRACT FROM AUTHOR]

We present the discovery of three new β Cep pulsators, three new pulsators with frequency groupings, and frequency patterns in a B3Ib star, all of which show pulsations with frequencies as high as about 17 d−1, with K2 space mission photometry. Based on a Fourier analysis and iterative pre-whitening, we present a classification and evaluate the potential for asteroseismic modelling. We include the lists of pulsation frequencies for three new β Cep pulsators, CD-28 12286, CD-27 10876, LS 3978, and additional pulsation mode frequencies for the known β Cep pulsator HD 164741. In addition, we characterize the regular frequency spacing found in the new pulsator HD 169173, and discuss its origin. We place the newly discovered variables in a colour–magnitude diagram using parallaxes from Gaia DR2 (second data release), showcasing their approximate location in the massive star domain. The identified frequency lists of these multiperiodic pulsators are a good starting point for future forward seismic modelling, after identification of at least one pulsation frequency from high-resolution time-series spectroscopy and/or multicolour photometry. [ABSTRACT FROM AUTHOR]

We outline a method using gradient flow independent component analysis (ICA) to separate signals comprising the coda in a topographically complex setting. We also identify the sources of scattered signals by tracking signal backazimuths over time. The gradient flow ICA method is shown to effectively separate signals in the acoustic coda. The method correctly identifies the backazimuth of the first arrival from two 800 kg TNT equivalent explosions as well as subsequent signals scattered by the surrounding topography. Circular statistics is used to analyse the variance, mean and uniformity of calculated backazimuths. These results have strong implications for understanding the acoustic wavefield by identifying scatterers and inverting for atmospheric conditions. [ABSTRACT FROM AUTHOR]

Context. Main sequence stars with a convective core are predicted to stochastically excite internal gravity waves (IGWs), which effectively transport angular momentum throughout the stellar interior and explain the observed near-uniform interior rotation rates of intermediate-mass stars. However, there are few detections of IGWs, and fewer still made using photometry, with more detections needed to constrain numerical simulations. Aims. We aim to formalise the detection and characterisation of IGWs in photometric observations of stars born with convective cores (M ≳ 1.5 M⊙) and parameterise the low-frequency power excess caused by IGWs. Methods. Using the most recent CoRoT light curves for a sample of O, B, A and F stars, we parameterised the morphology of the flux contribution of IGWs in Fourier space using an MCMC numerical scheme within a Bayesian framework. We compared this to predictions from IGW numerical simulations and investigated how the observed morphology changes as a function of stellar parameters. Results. We demonstrate that a common morphology for the low-frequency power excess is observed in early-type stars observed by CoRoT. Our study shows that a background frequency-dependent source of astrophysical signal is common, which we interpret as IGWs. We provide constraints on the amplitudes of IGWs and the shape of their detected frequency spectrum across a range of mass, which is the first ensemble study of stochastic variability in such a diverse sample of stars. Conclusions. The evidence of a low-frequency power excess across a wide mass range supports the interpretation of IGWs in photometry of O, B, A and F stars. We also discuss the prospects of observing hundreds of massive stars with the Transiting Exoplanet Survey Satellite (TESS) in the near future. [ABSTRACT FROM AUTHOR]

Abstract: Colliding sea surface waves generate the ocean microbarom, an acoustic signal that may transmit significant energy to the upper atmosphere. Previous estimates of acoustic energy flux from the ocean microbarom and mountain‐wind interactions are on the order of 0.01 to 1 mW/m2, heating the thermosphere by tens of Kelvins per day. We captured upgoing ocean microbarom waves with a balloon‐borne infrasound microphone; the maximum acoustic energy flux was approximately 0.05 mW/m2. This is about half the average value reported in previous ground‐based microbarom observations spanning 8 years. The acoustic flux from the microbarom episode described here may have heated the thermosphere by several Kelvins per day while the source persisted. We suggest that ocean wave models could be used to parameterize acoustically generated heating of the upper atmosphere based on sea state. [ABSTRACT FROM AUTHOR]

We present an 80-d long uninterrupted high-cadence K2 light curve of the B1Iab supergiant rho Leo (HD91316), deduced with the method of halo photometry. This light curve reveals a dominant frequency of frot = 0.0373 d-1 and its harmonics. This dominant frequency corresponds with a rotation period of 26.8 d and is subject to amplitude and phase modulation. The K2 photometry additionally reveals multiperiodic low-frequency variability (<1.5 d-1) and is in full agreement with low-cadence high-resolution spectroscopy assembled during 1800 d. The spectroscopy reveals rotational modulation by a dynamic aspherical wind with an amplitude of about 20 km s-1 in the Ha line, as well as photospheric velocity variations of a few kms-1 at frequencies in the range 0.2-0.6 d-1 in the Si III 4567Å line. Given the large macroturbulence needed to explain the spectral line broadening of the star, we interpret the detected photospheric velocity as due to travelling superinertial low-degree large-scale gravity waves with dominant tangential amplitudes and discuss why rho Leo is an excellent target to study how the observed photospheric variability propagates into the wind. [ABSTRACT FROM AUTHOR]

Introduction: Well-documented observations of earthgrazing meteoroids are exceptionally rare, with only a handful reported in scientific literature over the last five decades [1]. These objects are unique in that they enter the Earth's atmosphere at an extremely shallow angle relative to the horizon. An earthgrazing meteoroid might fully ablate, slow down enough to fall towards the Earth, or survive its passage through the atmosphere and exit back into space. While interacting with the denser regions of the atmosphere, an earthgrazing meteoroid might undergo ablation and produce a luminous path that could span as much as several hundreds of kilometers [2]. Earthgrazers generally do not penetrate deep into the atmosphere; documented cases had their minimum altitude between ~70 km and ~100 km [1]. During their passage through the atmosphere, sufficiently large and fast meteoroids produce shockwaves that can decay to very low frequency acoustic waves, also known as infrasound [3]. While it is relatively rare for high-altitude (≤100 km) meteoroids to produce infrasound detectable at ground-based stations, several instances had been documented in the past [4]. Earthgrazer Over Europe: A rare horizon-to-horizon earthgrazer event occurred over northern Europe on 22 September 2020 at 03:53:40 UTC, capturing attention of many eyewitnesses and numerous ground based cameras aimed at the skies (Figure 1) [5]. As per the analysis released by the Global Meteor Network [6], the luminous path of the earthgrazing fireball started over Germany and ended over the UK, at the altitude of 101 km and 107 km, respectively. The point of the closest approach was at ~90 km. The object's velocity upon the entry was ~34 km/s, and only slightly less, ~30 km/s, when it exited [5,6]. Infrasound Observations: Despite its high-altitude and apparently silent (to humans) passage, the earthgrazer was detected by infrasound sensors of the Royal Netherlands Meteorological Institute (KNMI) network [7] several minutes after it had entered the atmosphere. Three infrasound arrays recorded the signal: EXL, DBN, and CIA. The timeseries at one of the elements of the EXL array is shown in Figure 2 [8]. The signal arrived at a very steep angle at 03:58:44 UTC, a few minutes after the onset of a luminous path. Such arrival is indicative of a high altitude shock. Summary: This unique earthgrazing fireball event provides valuable constraints for infrasound propagation and characterization of high-altitude meteor events [4]. The extremely shallow entry angle of the fireball enabled the infrasound wave to readily propagate downward, thus assuming a direct path to the receiver. Detailed infrasound detection analyses and propagation modeling results will be discussed. [ABSTRACT FROM AUTHOR]

The persistence of treeless grasslands and sedgelands within a matrix of eucalypt and rainforest vegetation in the montane plateaux of northern Tasmania has long puzzled ecologists. Historical sources suggest that Tasmanian Aborigines were burning these treeless patches and models seeking to explain their maintenance generally include fire, soil properties and Aboriginal landscape burning. We aimed to provide a new historical perspective of the dynamics of the vegetation mosaics of Surrey Hills and Paradise Plains in north-west and north-east Tasmania, respectively, and used vegetation surveys and soil sampling to explore the role of vegetation and soils in these dynamics. Sequences of historical maps (1832 and 1903) and aerial photography showed that many treeless patches have persisted in the landscape since European settlement and that forests have rapidly expanded into the treeless patches since the early 1950s. Stand structure and floristic data described an expanding forest dominated by Leptospermum, which is consistent with vegetation succession models for the region. Soils under expanding forest boundaries did not have higher soil nitrogen or phosphorus than those under stable boundaries, signalling a lack of edaphic limitation to forest expansion. The magnitude of forest expansion at Paradise Plains (granite), Surrey Hills (basalt) and south-west Tasmania (quartzite) appears to follow a nutrient availability gradient and this hypothesis is backed by differences in soil phosphorus capital between the three systems. Given that existing vegetation boundaries in northern Tasmania do not coincide with soil nutrient gradients, we suggest that treeless vegetation was maintained by Aboriginal landscape burning and that the recent contraction of treeless vegetation is related to the breakdown of these fire regimes following European settlement. The observed rates of forest expansion could result in a substantial loss of these grasslands if sustained through this century and therefore our work supports the continuation of prescribed burning to maintain this high conservation value ecosystem. [ABSTRACT FROM AUTHOR]

Aim This paper reviews the biogeography of the Australian monsoon tropical biome to highlight general patterns in the distribution of a range of organisms and their environmental correlates and evolutionary history, as well as to identify knowledge gaps. Location Northern Australia, Australian Monsoon Tropics (AMT). The AMT is defined by areas that receive more than 85% of rainfall between November and April. Methods Literature is summarized, including the origin of the monsoon climate, present-day environment, biota and habitat types, and phylogenetic and geographical relationships of selected organisms. Results Some species are widespread throughout the AMT while others are narrow-range endemics. Such contrasting distributions correspond to present-day climates, hydrologies (particularly floodplains), geological features (such as sandstone plateaux), fire regimes, and vegetation types (ranging from rain forest to savanna). Biogeographical and phylogenetic studies of terrestrial plants (e.g. eucalypts) and animals (vertebrates and invertebrates) suggest that distinct bioregions within the AMT reflect the aggregated effects of landscape and environmental history, although more research is required to determine and refine the boundaries of biogeographical zones within the AMT. Phylogenetic analyses of aquatic organisms (fishes and prawns) suggest histories of associations with drainage systems, dispersal barriers, links to New Guinea, and the existence of Lake Carpentaria, now submerged by the Gulf of Carpentaria. Complex adaptations to the landscape and climate in the AMT are illustrated by a number of species. Main conclusions The Australian monsoon is a component of a single global climate system, characterized by a dominant equator-spanning Hadley cell. Evidence of hot, seasonally moist climates dates back to the Late Eocene, implying that certain endemic elements of the AMT biota have a long history. Vicariant differentiation is inferred to have separated the Kimberley and Arnhem Land bioregions from Cape York Peninsula/northern Queensland. Such older patterns are overlaid by younger events, including dispersal from Southeast Asia, and range expansions and contractions. Future palaeoecological and phylogenetic investigations will illuminate the evolution of the AMT biome. Understanding the biogeography of the AMT is essential to provide a framework for ecological studies and the sustainable development of the region. [ABSTRACT FROM AUTHOR]

Abstract: In nature, opportunities are limited for recording the response to a rapid ongoing base-level fall and for examining its effects on channel evolution during the process. Following a dramatic base-level fall, the natural laboratory area of the Dead Sea offers such an opportunity. Classical shape evolution models of incised channels describe the response to an "impulse" type base-level drop after it became stabilized. The Dead Sea delineates during its continuous level drop a different mode of adjustment from those previously conceptualized. We have recorded the entrenchment rates of channels and their transient shape evolution “at a station” in real time, i.e., during the ongoing base-level fall. This study represents the first attempt to apply integrated time series of high resolution DEMs, change detection maps, Differential Global Position System measurements, and field methods to monitor vertical and horizontal entrenchment rates, as well as the evolution of the cross-sectional shape of channels in response to a continuous and rapidly lowering base level. Mean vertical entrenchment rates are very high, 0.4–0.8 m/y, and widening rates are even higher (2.1–24 m/y). Elevation-change detection maps demonstrate along banks a patchy pattern of channel entrenchment, indicating the initial widening stage. The incised channels have a trapezoidal, gorge-like, cross-sectional form, i.e., they have developed beyond the initial stage of net vertical incision. However, neither advanced channel widening nor development of an inner floodplain has been observed. We conclude that widening is yet ineffective in damping the vertical adjustment. The continuous and rapid lowering of the Dead Sea level entraps the drainage systems in the vertical incision mode, preventing the evolutionary progression toward a wide, graded, and stable geometry which has been conceptualized in existing models. [Copyright &y& Elsevier]

In the last 8 yr, cotton (Gossypium hirsutum L.) growers in North Carolina have experienced variations in the year-to-year lint yield averages that range from a 56% increase to a 49% decrease. This variability results in wild fluctuations in income and a desire for more stable yields. Genetic structure may contribute to stability. This study was conducted to determine the impact of heterozygosity and heterogeneity on lint yield stability. Lint yield was observed in 18 environments over 3 yr among four population types that included homozygous lines grown in pure stands, homozygous lines grown in blended stands, hybrids grown in pure stands, and hybrids grown in blended stands. Comparisons were made using trait means, standard deviations, and the coefficients of variation (CVs) calculated over environments. There was no significant difference between lines grown in pure stands and blended lines with respect to yield or stability. Hybrids had a lower CV (were more stable) than homozygous lines. This stability was attributed to the hybrids and blends of hybrids out-yielding the homozygous lines and blends of homozygous lines in the low-yielding environments, but having similar yields in the high-yielding environments. These results do not support growing blends to increase stability or yield; however, growing hybrid cultivars could result in increased yields while reducing variability compared with current production practices. [ABSTRACT FROM AUTHOR]

Abstract: Coastal planform studies are a relevant initial stage before launching detailed dynamic field experiments. The aim of this study is to define the planform characteristics of 72 Catalan pocket beaches, natural and man-made, and to determine their sheltering effect, embaymentization and their status of equilibrium. Planform measurements were performed on SIGPAC, 1:5000 orthophoto sets and wave climate was provided by Puertos del Estado (Wana model). Planform parameters were applied and coastal planview indexes were determined. The study shows that the Catalan pocket beaches display a wide range of indentation, suggesting that no single structural, tectonic or morphological control dominates their planform. The man-made pocket beaches typically display indentations which are smaller than those shown by natural pocket beaches. Headland spacing and beach area are positively correlated. The more indented bays are, the shorter their beaches become. Low-indented pocket beaches are the widest and the longest ones. Deep indentation contributes towards beach protection and energy dissipation which counteracts rip efficiency and inhibits the formation of mega-rips. Pocket beaches often show gradual and moderate alongshore changes in texture and beach morphology. One third of the Catalan pocket beaches are “sediment starved”, i.e., 60% and more of their embayed shorelines are deprived of beach sediments. Examination of the status of equilibrium demonstrates that most of the Catalan pocket beaches are in an unstable mode, with indentation ratios that are unrelated to the wave obliquity. [Copyright &y& Elsevier]

Aim To study changes in woody vegetation in both floodplains and eucalypt savanna over a 40-year period using multi-temporal spatial analysis of variation in density of a large introduced herbivore, the Asian water buffalo ( Bubalus bubalis). Feral buffalo built up to high densities in the study area until c. 1985, after which a control programme almost eliminated the animals. From 1990, low densities of managed buffalo were maintained inside an enclosure. We compared trends in woody vegetation when buffalo were high-density feral, low-density managed or absent. Location The study area was located in and around a 116-km2 buffalo enclosure inside Kakadu National Park, in monsoonal northern Australia. Methods We analysed sequences of digitized and geo-rectified aerial photographs, acquired in 1964, 1975, 1984, 1991 and 2004, to chart changes in woody cover on the floodplain and in the savanna. On the floodplain we assessed whether trees were present at these times at 14,568 points, and buffalo density was estimated from the density of animal tracks. In the savanna we estimated woody cover at pre-selected sites. Generalized linear modelling was used to analyse changes in woody vegetation, using elevation and presence of woody vegetation in neighbouring points on the floodplain, and buffalo regime and initial woody cover in the savanna . Results Changes in animal track density reflected park-wide historical estimates of buffalo numbers. Tree cover increased in both floodplain and savanna, but this was only weakly related to buffalo density. The best predictor of whether a floodplain cell converted from treeless to woody, or the converse, was the woodiness of neighbouring vegetation. There was slightly less thickening with high buffalo densities. In savanna, low densities of managed buffalo were weakly associated with increases in tree cover relative to either high densities of feral buffalo or no buffalo. Main conclusions Our study indicates that buffalo are not a major driver of floodplain and eucalypt savanna dynamics. Rather, the observed increase in woody cover in both savanna and flood plains concords with regional trends and may be related to increased atmospheric CO2, increasing rainfall and changing fire regimes during the study period. [ABSTRACT FROM AUTHOR]

Historically, reselection, pedigree, and mass-selection breeding methods have been used to develop open-pollinated cultivars of upland cotton (Gossypium hirsutum L.). As a result, modern cotton cultivars should have accumulated additive genetic effects with time, while also possessing fewer nonadditive gene effects than obsolete cultivars. A topcross test was conducted to compare the heterotic effects of obsolete and modern cultivars for yield, yield components, and fiber quality. Significant differences were detected between heterosis values for the modern and obsolete cultivar groups for seed cotton yield, lint yield, lint percentage, and boll weight. No significant heterotic effects were detected for fiber quality. The obsolete group of cultivars showed average lint yield heterosis values of 34% compared with 23% for the modern cultivars. Both cultivar groups displayed significant, but similar heterosis values for the number of boils per square meter (17 and 15%, respectively). The major yield component associated with lint yield heterosis for both groups was boils per square meter, although boll weight heterosis also contributed to lint yield heterosis for the obsolete cultivars. Although modern cultivars produced considerable heterotic effects for yield, this study demonstrates that obsolete cultivars may provide an additional source of non-additive genetic effects that can be exploited in a hybrid production system. [ABSTRACT FROM AUTHOR]

The article discusses the importance of dendrochronology to land manager, fire ecologist and global change biologist in order to date the past fire events which are manifested by injuries on the trunks on long-lived trees. It states that dendrochronology traces the fire scars or records of past landscape fire activity with unparalleled temporal resolution. Global climate change is also a factor that easily acquires fire data and understanding the relationship with interannual and multidecadal climate cycles.

Abstract: Two studies were performed to examine the efficacy of milbemycin oxime against fourth-stage larvae or adults of Toxocara cati. In the study to determine efficacy against fourth-stage larvae, 20 domestic shorthair cats were inoculated with 500 embryonated eggs. Four weeks after inoculation, the animals were allocated to two groups, and cats in one group were treated with medicated tablets containing 4mg milbemycin oxime and 10mg praziquantel (MILBEMAX®) and cats in the other group with placebo tablets. Seven days after treatment the animals were euthanatized and necropsied for worm counting. The number of worms found was significantly (p =0.0002) lower in cats treated with medicated tablets than in cats treated with placebo tablets. The reduction in the number of worms was 96.53%. In the study to determine efficacy against mature adult worms, 13 kittens were inoculated with T. cati embryonated eggs. On day 45 after inoculation and after the infection had been confirmed through faecal examinations for 11 out of the 13 animals, the 11 infected animals were allocated to two groups and treated as in the first study. Seven days after treatment, all animals were euthanatized and necropsied for worm counting. The number of worms found was significantly (p =0.0043) lower in kittens treated with medicated tablets than in kittens treated with placebo tablets. The reduction in the number of worms was 95.90%. No adverse effects were recorded during either study. It is concluded that the milbemycin oxime–praziquantel tablets that were used are efficacious for the control of T. cati infections in cats. [Copyright &y& Elsevier]

Allosyncarpia ternata (an angiosperm) and Callitris intratropica (a gymnosperm) are two fire-sensitive tree species of the Australian monsoonal tropics. Studies using historical aerial photography have revealed recent expansion of A. ternata rainforests. There has simultaneously been a widespread collapse of C. intratropica populations in northern Australian savannas, presumably because of cessation of traditional Aboriginal landscape burning. To explain the demography behind these contrasting trends, stand structure, survival, and growth of the two species were recorded over a 16-year period at the boundary of a rainforest patch and also in adjacent savanna, in Kakadu National Park. Ages of the largest trees of each species, estimated by using a Bayesian analysis of tree-diameter increments, were approximately 433 years for A. ternata and 235 years for C. intratropica on the rainforest boundary, and 417 years for C. intratropica in the adjacent savanna. Densities of juveniles (seedlings and re-sprouts <0.5 m high) were 325–6,000 times higher for A. ternata than for C. intratropica. Life-table calculations indicated there was sufficient recruitment of A. ternata, but not C. intratropica, to overcome observed mortality rates and maintain a stable population. This is almost certainly because A. ternata re-sprouts prolifically after fire whereas C. intratropica is an obligate seeder. These results highlight the critical need for careful fire management to maintain populations of a characteristic Australian gymnosperm over much of its range. [ABSTRACT FROM AUTHOR]

Soil organic matter (SOM) was sampled from soil profiles on a near level sandsheet at the southern limit of the Tanami Desert in central Australia to determine if boundaries of Triodia hummock grassland-Acacia aneura shrublands had changed in the Holocene. Accelerator Mass Spectrometry (AMS) 14C dating of 16 soil profiles showed that SOM that had accumulated at 100 to 140 cm depth, (near the base of most profiles) had ages between 1175 and 2630 14C years, averaging 1906 14C years. The stable carbon isotopic (ƍ13C) composition of SOM from the upper 50 cm soil profiles in the A. aneura shrubland (inhabited by plants with predominantly C3 photosynthetic pathway) was significantly more 13C-depleted than the comparable soil interval beneath a Triodia grassland (predominantly C4 photosynthetic pathway). Mean age of SOM at 50 cm depth was 830 14C years, suggesting the vegetation has been stable for about 1000 years. However, soil profiles in Triodia grassland adjacent to the shrubland boundary had slightly more depleted ƍ13C relative to sites >0.5 km from the boundary. With respect to stable nitrogen isotopic values, only surface soils in the Acacia shrublands were found to be 15N-enriched relative to all other soil depths. Although there were no obvious environmental discontinuities, such as change in soil type or slope angle, associated with the ecosystem boundaries, the Acacia shrublands were found to occur on more clayrich soils with higher concentrations of total phosphorus, nitrogen and potassium compared with the surrounding grasslands, and these trends became more pronounced with increasing distance from the ecotone: it is unclear if these differences are a cause or an effect of the vegetation mosaic. The concordance of the vegetation boundaries with the ƍ13C and ƍ15N and of soil nutrients are consistent with only minor attrition of the A. aneura shrublands in the late Holocene at this site. [ABSTRACT FROM AUTHOR]

We use the method of generating functions to find the limit of a q-continued fraction, with 4 parameters, as a ratio of certain q-series. We then use this result to give new proofs of several known continued fraction identities, including Ramanujan's continued fraction expansions for (q2; q3)∞/(q; q3)∞ and $(q;q^{2})_{\infty}/(q^{3};q^{6})_{\infty}^{3}$. In addition, we give a new proof of the famous Rogers–Ramanujan identities. We also use our main result to derive two generalizations of another continued fraction due to Ramanujan. [ABSTRACT FROM AUTHOR]

The article focuses on the importance of understanding fire ecology. This understanding includes the direct and indirect effects of fire disturbance on plants and animals. Aside from ecology, another science disciplines are investigating the impact of landscape fire disturbance on hydrological systems as part of the emerging field of ecohydrology. An understanding on the effects of landscape fire on ecohydrological systems is needed especially with the threat of global environmental changes including the increased frequency and intensity of landscape fires.

Abstract: Panion™ fibre is prepared from a high molecular weight version of chlorine and defect free polyaniline (PANI). It is processed into textile fibre by continuous wet spinning techniques. The room temperature DC conductivity for unstretched and stretched (5x at 373K) high molecular weight samples was 72 and 725Ω−1 cm−1, respectively. Resistivity measurements of Panion™, from 4 to 350K, indicate that the fibre manufacturing process and the polymer synthetic route both serve to minimize structural disorder in the solid-state. The transport resides on the metallic side of the metal-insulator (M-I) phase boundary for unstretched and stretched fibre samples prepared from high Mw PANI emeraldine base. The monofilament fibre can be formed into yarns for weaving fabric, braided into 2- and 3- dimensional structures, or used to form knitted fabrics, all with tunable electronic functionality. [Copyright &y& Elsevier]

Provides an overview on a fire ecology research that has emphasize the importance of the landscape scale. Benefits of satellite imagery to fire ecologists; Study of fire patterns in southern African savannas which emphasize the importance of land management; Importance of climate and fire management influencing fire activity.

1. An individual evergreen leaf in the northern Australian savanna biome experiences seasonal extremes in rainfall, raising questions of whether there is a corresponding shift in the physiology of these leaves, and whether estimates of leaf function for the biome differ between wet and dry seasons.2. A range of leaf attributes was measured for 21 tree species in four contrasting habitats during the wet season, and again during the dry season for the 14 species that retained leaves.3. The 14 leaf-retaining species showed decreases in assimilation rates, foliar saturated water content and chlorophyll content, and increases in leaf mass per area and leaf density between wet and dry seasons. Species means were strongly correlated between seasons for attributes other than assimilation and stomatal conductance.4. Seasonal variation in CO2 assimilation rates was larger in non-Myrtaceous species than in the leaf-retaining Myrtaceous species that largely dominate the biome, and also varied considerably among the four habitats, which had different edaphic conditions. Assimilation per unit mass decreased between the wet and dry seasons by only 5% in theMelaleucaswamp and 17% in theEucalyptusopen forest, compared with 47% in the dry monsoon forest and 57% in the mixed woodland.5. Biome means differed between seasons because wet-season means included measurements of fully deciduous species which tended to have large, thin, nitrogen-rich leaves.Functional Ecology(2004)18, 707–718 [ABSTRACT FROM AUTHOR]

This study of contemporary landscape burning patterns in the North Kimberley aims to determine the relative influences of environmental factors and compare the management regimes occurring on Aboriginal lands, pastoral leases, national park and crown land. The study area is defined at the largest scale by Landsat Scene 108–70 that covers a total land area of 23,134 km2 in the North Kimberley Bioregion of north-west Australia, including the settlement of Kalumburu, coastline between Vansittart Bay in the west and the mouth of the Berkeley River in the east, and stretching approximately 200 km inland. Two approaches are applied. First, a 10-year fire history (1990–1999) derived from previous study of satellite (Landsat-MSS) remote sensing imagery is analysed for broad regional patterns. And secondly, a 2-year ground-based survey of burning along major access roads leading to an Aboriginal community is used to show fine-scale burning patterns. anova and multiple regression analyses are used to determine the influence of year, season, geology, tenure, distance from road and distance from settlement on fire patterns. Satellite data indicated that an average of 30.8% (±4.4% SEM) of the study area was burnt each year with considerable variability between years. Approximately 56% of the study area was burnt on three or more occasions over the 10-year period. A slightly higher proportion of burning occurred on average in the late dry season (17.2 ± 3.6%), compared with the early dry season (13.6 ± 3.3%). The highest fire frequency occurred on basalt substrates, on pastoral tenures, and at distances 5–25 km from roads. Three-way anova demonstrated that geological substrate and land use were the most significant factors influencing fire history, however a range of smaller interactions were also significant. Analysis of road transects, originating from an Aboriginal settlement, showed that the timing of fire and geology type were the most significant factors affecting the pattern of area burnt. Of the total transect area, 28.3 ± 2.9% was burnt annually with peaks in burning occurring into the dry season months of June, August and September. Basalt uplands (81.2%) and lowlands (30.1%) had greater areas burnt than sandstone (12.3%) and sands (17.7%). Anthropogenic firing is constrained by two major environmental determinants; climate and substrate. Seasonal peaks in burning activity in both the early and late dry season relate to periods of optimal fire-weather conditions. Substrate factors (geology, soils and physiognomy) influence vegetation-fuel characteristics and the movement of fire in the landscape. Basalt hills overwhelmingly supported the most frequent wildfire regime in the study region because of their undulating topography and relatively fertile soils that support perennial grasslands. Within these spatial and temporal constraints people significantly influenced the frequency and extent of fire in the North Kimberley thus tenure type and associated land uses had a significant influence on fire patterning. Burning activity is high on pastoral lands and along roads and tracks on some tenure types. While the state government uses aerial control burning and legislation to try to restrict burning to the early dry season across all geology types, in practice burning is being conducted across the full duration of the dry season with early dry season burning focused on sandstone and sand substrates and late dry season burning focused on basalt substrates. There is greater seasonal and spatial variation in burning patterns on landscapes managed by Aboriginal people. [ABSTRACT FROM AUTHOR]

To compare woody vegetation of Eucalyptus tetrodonta savanna in an area that has had near continuous management by Aboriginal people with that of an area managed by neither Aborigines nor Europeans for the last 50 years. In particular, we tested the hypothesis that Aboriginal landscape burning increases the abundance of tree species, particularly those that bear edible fruit. We also examined whether Aboriginal burning increases tree density of the mid-layer using measurements of the density and size distribution of all trees. Central Arnhem Land, a stronghold of traditional Aboriginal culture, in the Australian monsoon tropics. Previous remote sensing analyses have shown that over the decade prior to field sampling, fires in the unmanaged area had produced a coarse-scale mosaic of patches burnt between one to three times, in contrast the area under Aboriginal management was characterized by very high spatial and temporal variability of fire activity. In the study reported here, we assessed density, size distribution and taxonomic identity of trees in 78 and 79 plots (each 79–1385 m2 in area) in the managed and unmanaged areas, respectively. Habitat attributes such as cover of rocks and bare ground and cover of various life forms were visually assessed for each plot, and density of grass and leaf litter was measured. Despite the contrasting fire regimes there were only minor differences in the fine fuels between the two areas, both of which had a low biomass of grass (dry weight was 35–221 g m−2). The composition and overall density of woody species was similar in the two areas but densities of fruit tree species and eucalypts were significantly higher, particularly in middle of the size class distribution of stems, in the unmanaged area while a few species, such as the fire sensitive conifer Callitris intratropica, were more abundant in the managed area. Our findings suggest that current Aboriginal landscape burning has a significant impact on vegetation structure, specifically stems in the middle of the size class distribution, but little effect on either species composition or total tree density. Such burning reduced the abundance of fruit bearing trees but had little effect on grass or fine fuel biomass. The vegetation structure in the area managed by Aborigines was similar to that reported for many savannas subjected to European fire regimes; a core difference, however, was lower biomass of tall grasses and greater abundance of C. intratropica. These data provide important empirical corroboration of previous descriptive ethnographic and historical analyses that vegetation structure at the time of settlement was strongly influenced by indigenous peoples’ use of fire. Thus our results not only inform contemporary land management but also provide insights into the role humans played in the evolution of Australia's remarkably flammable flora. Given our inability to use a replicated experimental design the generality of these conclusions require testing by comparing the findings of allied studies conducted elsewhere in northern Australia. [ABSTRACT FROM AUTHOR]

Abstract The history of isolated patches of monsoon rainforest within large tracts of Eucalyptus savanna is poorly understood because of the scarcity of reliable palaeoecological records in the Australian monsoon tropics. Elsewhere in the world, the ratio of the stable isotopes 13 C to 12 C (δ13 C) in soil organic matter has shed light on the dynamics of rainforest–savanna boundaries because tropical grasses with the C4 photosynthetic pathway have a distinct δ13 C signature (–17 to –9‰) compared with that of woody plants with the C3 photosynthetic pathway (–32 to –22‰). In order to determine the magnitude of the variation in δ13 C, unreplicated soil profiles were sampled beneath different vegetation types on three boundaries between Eucalyptus savanna and rainforest that were both growing on Tertiary age laterite parent material. Replicated (n = 3) soil profiles, which were also derived from Tertiary age laterite, were sampled from beneath: (i) dense stands of African grasses within a frequently burnt Eucalyptus savanna; and within the same long unburnt Eucalyptus savanna, (ii) patches of African and natives grasses and (iii) clumps of Acacia trees. The strongly negative δ13 C values of soil organic matter derived from the frequently burnt and long unburnt grassy understoreys in the Eucalyptus savannas showed that a considerable amount of the soil carbon was derived from C3 (woody) species despite the presence of a ground layer dominated by C4 grasses. However, a feature of these data was the considerable variability among the three ‘replicate’ profiles. The surface soil samples from beneath three clumps of Acacia trees in the unburnt Eucalyptus savanna had much less variable δ13 C values and were similar to two of the three monsoon rainforests sampled. The pattern of δ13 C... [ABSTRACT FROM AUTHOR]

Abstract 1 Analysis of digitized aerial photographs taken in 1941 and 1994, using image processing and geographical information system technology, enabled the quantification of change in the coverage of forest and grassland patches that occur within a Eucalyptus savanna matrix in a subcoastal region of the Australian monsoon tropics. The 3058 ha study area was orientated along a low escarpment that separated a sandstone plateau from lowlands that comprised 58% and 42% of the area, respectively. 2 In the 53-year period, humans modified less than 1% of the study area, primarily for road building, and primarily in savanna areas. More than 85% of the study area at both sample times was covered by savanna. However, over the same period, the forest coverage increased from 5.03% to 9.91% of the study area and coverage of grassland decreased from 6.70% to 2.47%. The aerial photography also showed that tree density in the savanna had increased, although this was not assessed quantitatively. 3 There was an increase in the number of forest patches from 116 to 142. The number of grassland patches decreased (particularly those > 1 ha) from 87 to 59, although the size class distribution of forest and grassland patches was statistically similar for both sample times. 4 A 50-m GIS buffer was used to distinguish creek-lines environments from surrounding catchments. Using this criterion, 14% of the study area was classified as plateau creek-lines and 9% lowland creek-lines. Although the expansion of forest and loss of grassland varied significantly amongst catchment and creek-lines on the plateau and lowlands, the 1941 rank order of coverage of each vegetation type was maintained in these four landscape categories in 1994. In both years the greatest extent of forest and grassland occurred on the lowland catchments, despite their accounting for only one-third of the study area. 5 Transition matrices for vegetation change among the four landscape categories demonstrated that,... [ABSTRACT FROM AUTHOR]

Focuses on the biota of the Eucalyptus diversicolor forests of southwestern Australia. Issues concerning the definition of Australian rainforest; Description of the trees; Trees and other associated plant and animal species that are adapted to recurrent wildfires; Diversification of eucalyptus and associated biota.

Earth's ionosphere has long been targeted as a medium for remote sensing of explosive terrestrial events such as earthquakes, volcanic eruptions, and nuclear/conventional weapon detonations. Until now, the only confirmed ionospheric detections have been of very large events that were easily detectable through other traditional global sensor systems (e.g., seismic). We present the first clear, confirmed detections of relatively low yield 1‐ton TNT‐equivalent chemical explosions using pulsed Doppler radar observations of isodensity layers in the ionospheric E region. The shape and spectra of the detected waveforms closely match predictions from the acoustic ray tracing and weakly nonlinear waveform propagation models. The explosions were roughly three orders of magnitude lower yield than any previous confirmed ionospheric detection and represent the first conclusive evidence that explosions of this size can have clear impacts on the ionosphere. This technique could improve the remote detection of both anthropogenic and natural explosive events. Plain Language Summary: Explosions, even of modest yield, generate copious amounts of acoustic waves across a wide range of frequencies. While the high frequencies are quickly absorbed by the atmosphere, the lowest frequencies, in the sub‐audible infrasound part of the spectrum, are capable of traveling to great distances. Typically this infrasound is detected on the ground using highly sensitive listening equipment such as microbarometers. We present a different method, however, where we utilize the fact that the upper atmosphere is ionized (the ionosphere) and is therefore a good target for a radar. As the sound wave passes through the ionosphere it sloshes the bulk ions such that it shows up an oscillating radar target. We use this new technique to clearly detect explosions with yields of 1‐ton TNT equivalent. These detections are 500 times smaller than previous confirmed detections using the ionosphere as a sensor for explosions. Key Points: Infrasound from 1‐ton TNT‐equivalent chemical explosions are clearly detectable using pulsed Doppler radar of the ionosphereObservations match the modeled temporal and spectral predictions of infrasound propagationStrong azimuthal differences in waveform shape and strength could be caused by uneven terrain or complex wind fields [ABSTRACT FROM AUTHOR]

One of the most complex and contentious issues in Australian ecology concerns the environmental impact of Aboriginal landscape burning. This issue is not only important for the development of a comprehensive understanding of the dynamics and evolution of the Australian biota, but is central to the formulation of appropriate strategies for the conservation of the nation's biodiversity. Ethnographic evidence leaves little doubt that Aboriginal burning played a central role in the maintenance of the landscapes subsequently colonized by Europeans. Both 19th century European colonists and anthropologists in the 20th century documented the indispensability of fire as a tool in traditional Aboriginal economies, which have aptly been described as 'fire-stick farming'. Aborigines used fire to achieve short-term outcomes such as providing favourable habitats for herbivores or increasing the local abundance of food plants, but it is not clear whether or not Aborigines had a predictive ecological knowledge of the long-term consequences of their use of fire. A large body of ecological evidence suggests that Aboriginal burning resulted in substantial changes in the geographic range and demographic structure of many vegetation types. Aboriginal burning was important in creating habitat mosaics that favoured the abundance of some mammal species and in the maintenance of infrequently burnt habitats upon which the survival of specialized fauna depends. Aboriginal fire regimes were probably critical for the maintenance of at least one species of tree (Callitris intratropica) in the monsoon tropics. The question of the original impact of humans on the Australian environment is fundamentally speculative because of vague, disputed time frames proposed for the waves of colonization and shifting settlement patterns of Aborigines in the late Quaternary period. There is an inherent circular argument concerning the cause and effect of climatic change, vegetation change, and burning through the late Quaternary. Charcoal and pollen evidence from long sedimentary cores is ambiguous and cannot be used to demonstrate unequivocally the initial impact of Aboriginal people on the landscape of Pleistocene Australia. The sparse available evidence does not support the hypotheses that Aboriginal burning was primarily responsible for the extinction of Pleistocene megafauna; was critical for the maintenance of habitats of small mammals that have become extinct following European colonization; initiated widespread accelerated soil erosion rates in either the Pleistocene or Holocene; or forced the evolutionary diversification of the Australian biota. Burning may have caused the extinction of some fire-sensitive species of plants and animals dependent upon infrequently burnt habitats, and it must have maintained structurally open vegetation such as grasslands and also extended the range of fire-adapted species, such as Eucalyptus, into environments climatically suitable for rain forest. Palaeoecological research concerning prior impacts of Aborigines must give way to focused studies of the role of different anthropogenic fire regimes in contemporary ecosystems that have not been destroyed by European colonization. Such research is crucial for comprehending the role of Aboriginal burning in the maintenance of Australia's unique, rich biodiversity. [ABSTRACT FROM AUTHOR]

Presents a letter to the editor on the rapid transformation of a treeless riverine grassland to a dense woodland in Northwest Territories.

Provides information on a study which determined minimum-drag shapes for missile nose cones in rarefied flow using kinetic theory. Gas-surface interactions; Numerical minimum-drag results; Conclusions.

Surveys in the Milky Way and Large Magellanic Cloud have revealed that the majority of massive stars will interact with companions during their lives. However, knowledge of the binary properties of massive stars at low metallicity, and therefore in conditions approaching those of the Early Universe, remain sparse. We present the Binarity at LOw Metallicity (BLOeM) campaign, an ESO large programme designed to obtain 25 epochs of spectroscopy for 929 massive stars in the Small Magellanic Cloud, allowing us to probe multiplicity in the lowest-metallicity conditions to date (Z = 0.2 Z⊙). BLOeM will provide (i) the binary fraction, (ii) the orbital configurations of systems with periods of P ≲ 3 yr, (iii) dormant black-hole binary candidates (OB+BH), and (iv) a legacy database of physical parameters of massive stars at low metallicity. Main sequence (OB-type) and evolved (OBAF-type) massive stars are observed with the LR02 setup of the GIRAFFE instrument of the Very Large Telescope (3960–4570 Å resolving power R = 6200; typical signal-to-noise ratio(S/N) ≈70–100). This paper utilises the first nine epochs obtained over a three-month time period. We describe the survey and data reduction, perform a spectral classification of the stacked spectra, and construct a Hertzsprung-Russell diagram of the sample via spectral-type and photometric calibrations. Our detailed classification reveals that the sample covers spectral types from O4 to F5, spanning the effective temperature and luminosity ranges 6.5 ≲ Teff/kK ≲ 45 and 3.7 < log L/L⊙ < 6.1 and initial masses of 8 ≲ Mini ≲ 80 M⊙. The sample comprises 159 O-type stars, 331 early B-type (B0–3) dwarfs and giants (luminosity classes V–III), 303 early B-type supergiants (II–I), and 136 late-type BAF supergiants. At least 82 stars are OBe stars: 20 O-type and 62 B-type (13% and 11% of the respective samples). In addition, the sample includes 4 high-mass X-ray binaries, 3 stars resembling luminous blue variables, 2 bloated stripped-star candidates, 2 candidate magnetic stars, and 74 eclipsing binaries. [ABSTRACT FROM AUTHOR]

Massive stars (those ≥8 solar masses at formation) have radiative envelopes that cannot sustain a dynamo, the mechanism that produces magnetic fields in lower-mass stars. Despite this, approximately 7% of massive stars have observed magnetic fields, the origin of which is debated. We used multi-epoch interferometric and spectroscopic observations to characterize HD 148937, a binary system of two massive stars. We found that only one star is magnetic and that it appears younger than its companion. The system properties and a surrounding bipolar nebula can be reproduced with a model in which two stars merged (in a previous triple system) to produce the magnetic massive star. Our results provide observational evidence that magnetic fields form in at least some massive stars through stellar mergers. [ABSTRACT FROM AUTHOR]

We present the first asteroseismic results for δ Scuti and γ Doradus stars observed in Sectors 1 and 2 of the TESS mission. We utilize the 2-min cadence TESS data for a sample of 117 stars to classify their behaviour regarding variability and place them in the Hertzsprung–Russell diagram using Gaia DR2 data. Included within our sample are the eponymous members of two pulsator classes, γ Doradus and SX Phoenicis. Our sample of pulsating intermediate-mass stars observed by TESS also allows us to confront theoretical models of pulsation driving in the classical instability strip for the first time and show that mixing processes in the outer envelope play an important role. We derive an empirical estimate of 74 per cent for the relative amplitude suppression factor as a result of the redder TESS passband compared to the Kepler mission using a pulsating eclipsing binary system. Furthermore, our sample contains many high-frequency pulsators, allowing us to probe the frequency variability of hot young δ Scuti stars, which were lacking in the Kepler mission data set, and identify promising targets for future asteroseismic modelling. The TESS data also allow us to refine the stellar parameters of SX Phoenicis, which is believed to be a blue straggler. [ABSTRACT FROM AUTHOR]