J. B. Climent, J. C. Guirado, M. Pérez-Torres
et al.
Radio observations of ultracool dwarfs, objects comprising brown dwarfs and the very lowest mass stars, have mainly focused on analyzing their light-curve and spectral energy distributions providing valuable insights into their magnetic fields. However, spatially-resolved studies of such magnetospheres have been elusive so far. Radio interferometric observations of the brown dwarf LSR J1835+3259 reveal an extended magnetosphere with a morphology compatible with the presence of a radiation belt, similar to that of Jupiter and Earth, consisting of energetic particles confined via magnetic mirroring. Our finding suggests that radio emitting ultracool dwarfs may behave as scaled up versions of Jupiter, validating the connection between dipole-ordered magnetic fields and the presence of belt-like morphologies and aurorae beyond our Solar System.
Historicamente, as primeiras soluções da relatividade geral não foram reconhecidas como soluções de buracos negros. Elas foram, a princípio, idealizadas para descrever o campo gravitacional de objetos massivos esfericamente simétricos, como o Sol ou o elétron. Neste artigo, vamos apresentar as soluções de buracos negros em seu contexto histórico e mostrar como a nossa compreensão sobre o universo mudou à medida que desvendamos propriedades fundamentais sobre estes campos gravitacionais. O objetivo é apresentar uma introdução histórica sobre a relatividade geral e buracos negros, focada na teoria de gravitação e suas interpretações, como apoio didático para aqueles que pretendem iniciar os estudos sobre o tema.
We present a vectorial formalism to determine the approximate solutions to the problem of a composite body made of $L$ homogeneous, rigidly rotating layers bounded by spheroidal surfaces. The method is based on the 1st-order expansion of the gravitational potential over confocal parameters, thereby generalizing the method described in Paper I for $L=2$. For a given relative geometry of the ellipses and a given set of mass-density jumps at the interfaces, the sequence of rotation rates and interface pressures is obtained analytically by recursion. A wide range of equilibria result when layers rotate in an asynchronous manner, although configurations with a negative oblateness gradient are more favorable. In contrast, states of global rotation (all layers move at the same rate), found by solving a linear system of $L-1$ equations, are much more constrained. In this case, we mathematically demonstrate that confocal and coelliptical configurations are not permitted. Approximate formula for small ellipticities are derived. These results reinforce and prolongate known results and classical theorems restricted to small elliptiticities. Comparisons with the numerical solutions computed from the Self-Consistent-Field method are successful.
Identifying long-period eclipsing binaries with space-based photometry is still a challenge even in the century of space telescopes due to the relatively short observation sequences and short lifetime of these missions. The Transiting Exoplanet Survey Satellite (TESS) space telescope is an appropriate tool to supplement previous space-based observations. In this paper we report the first results of the eclipse timing variation (ETV) analyses of eclipsing binaries (EBs) measured by CoRoT and TESS space telescopes. Among the 1428 EB candidates we found 4 new potential triple candidates, for which ETV was analysed and fitted by the well-known light-travel-time effect (LTTE). One of them shows significant phase shift in its folded light curve which required extra care. In this paper we also present some other systems showing significant ETV signals that could be explained by mass transfer or apsidal motion.
Kim Miskovetz, Trent J. Dupuy, Jessica Schonhut-Stasik
et al.
The majority of stars have one or more stellar companions. As exoplanets continue to be discovered, it is crucial to examine planetary systems to identify their stellar companions. By observing a change in proper motion, companions can be detected by the acceleration they induce on their host stars. We selected 701 stars from the Hipparcos-Gaia Catalog of Accelerations (HGCA) that have existing adaptive optics imaging data gathered with Gemini/NIRI. Of these, we examined 21 stars known to host planet candidates and reduced their archival NIRI data with Gemini's DRAGONS software. We assessed these systems for companions using the NIRI images as well as Renormalized Unit Weight Error values in Gaia and accelerations in the HGCA. We detected three known visible companions and found two more systems with no visible companions but astrometric measurements indicating likely unresolved companions.
The advent of increasingly large and complex datasets has fundamentally altered the way that scientists conduct astronomy research. The need to work closely to the data has motivated the creation of online science platforms, which include a suite of software tools and services, therefore going beyond data storage and data access. We present two example applications of Jupyter as a part of astrophysical science platforms for professional researchers and students. First, the Astro Data Lab is developed and operated by NOIRLab with a mission to serve the astronomy community with now over 1500 registered users. Second, the Dark Energy Spectroscopic Instrument science platform serves its geographically distributed team comprising about 900 collaborators from over 90 institutions. We describe the main uses of Jupyter and the interfaces that needed to be created to embed it within science platform ecosystems. We use these examples to illustrate the broader concept of empowering researchers and providing them with access to not only large datasets but also cutting-edge software, tools, and data services without requiring any local installation, which can be relevant for a wide range of disciplines. Future advances may involve science platform networks, and tools for simultaneously developing Jupyter notebooks to facilitate collaborations.
PURPOSE Although the wind, rain, and flooding of Hurricane Maria in Puerto Rico abated shortly after its landfall on September 20, 2017, the disruption of the electrical, communications, transportation, and medical infrastructure of the island was unprecedented in scope and caused lasting harm for many months afterward. A compilation of recommendations from radiation oncologists who were in Puerto Rico during the disaster, and from a panel of American Society for Radiation Oncology (ASTRO) cancer experts was created. METHODS AND MATERIALS Radiation oncologists throughout Puerto Rico collaborated and improvised to continue treating patients in the immediate aftermath of the storm and as routine clinical operations were restored gradually. Empirical lessons from the experience of radiation therapy administration in this profoundly altered context of limited resources, impaired communication, and inadequate transportation were organized into a recommended template, applicable to any radiation oncology practice. ASTRO disease-site experts provided evidence-guidelines for mitigating the impact of a 2- to 3-week interruption in radiation therapy. RESULTS Practical measures to mitigate the medical impact of a disaster are summarized within the framework of "Prepare, Communicate, Operate, Compensate." Specific measures include the development of an emergency operations plan tailored to specific circumstances, prospective coordination with other radiation oncology clinics before a disaster, ongoing communications with emergency management organizations, and routine practice of alternate methods to disseminate information among providers and patients. CONCLUSIONS These recommendations serve as a starting point to assist any radiation oncology practice in becoming more resiliently prepared for a local or regional disruption from any cause. Disease-site experts provide evidence-based guidelines on how to mitigate the impact of a 2- to 3-week interruption in radiation therapy for lung, head and neck, uterine cervix, breast, and prostate cancers through altered fractionation or dose escalation.
Protoplanetary discs are complex dynamical systems where several processes may lead to the formation of ring-like structures and planets. These discs are flared following a profile where the vertical scale height increases with radius. In this work, we investigate the role of this disc flaring geometry on the formation of rings and holes. We combine a flattening law change with X-ray and FUV photoevaporative winds. We have used a semi-analytical 1D viscous α approach, presenting the evolution of the disc mass and mass rate in a grid of representative systems. Our results show that changing the profile of the flared disc may favour the formation of ring-like features resembling those observed in real systems at the proper evolutionary times, with proper disc masses and accretion rate values. However, these features seem to be short-lived and further enhancements are still needed for better matching all the features seen in real systems.
A test particle in a noncoplanar orbit about a member of a binary system can undergo Kozai-Lidov oscillations in which tilt and eccentricity are exchanged. An initially circular highly inclined particle orbit can reach high eccentricity. We consider the nonlinear secular evolution equations previously obtained in the quadrupole approximation. For the important case that the initial eccentricity of the particle orbit is zero, we derive an analytic solution for the particle orbital elements as a function of time that is exact within the quadrupole approximation. The solution involves only simple trigonometric and hyperbolic functions. It simplifies in the case that the initial particle orbit is close to being perpendicular to the binary orbital plane. The solution also provides an accurate description of particle orbits with nonzero but sufficiently small initial eccentricity. It is accurate over a range of initial eccentricity that broadens at higher initial inclinations. In the case of an initial inclination of pi/3, an error of 1% at maximum eccentricity occurs for initial eccentricities of about 0.1.
Robert F. Cahalan, Paulino Ajiquichi, Gaspar Yataz
For a "reference day" of minimal solar activity between cycles 23 and 24 we compute the brightness temperature from solar spectral irradiance for each wavelength. We consider small variations of irradiance and temperature about the reference day values, and derive linear and quadratic analytic temperature approximations by Taylor expansion about the reference values. To determine approximation accuracy we compare to exact brightness temperatures computed for each day. We find that the linear analytic approximation overestimates, while the quadratic underestimates the exact result. Using R software, we find statistical fit models with minimum root-mean-square-error. We show that the quadratic statistical fit models give the smallest root-mean-square-error, giving results very near the exact.
Differential atmospheric dispersion is a wavelength-dependent effect introduced by Earth's atmosphere that affects astronomical observations performed using ground-based telescopes. It is important, when observing at a zenithal angle different from zero, to use an Atmospheric Dispersion Corrector (ADC) to compensate this atmospheric dispersion. The design of an ADC is based on atmospheric models that, to the best of our knowledge, were never tested against on-sky measurements. We present an extensive models analysis in the wavelength range of 315-665 nm. The method we used was previously described in the paper I of this series. It is based on the use of cross-dispersion spectrographs to determine the position of the centroid of the spatial profile at each wavelength of each spectral order. The accuracy of the method is 18 mas. At this level, we are able to compare and characterize the different atmospheric dispersion models of interest. For better future ADC designs, we recommend to avoid the Zemax model, and in particular in the blue range of the spectra, when expecting residuals at the level of few tens of milli-arcseconds.
Summary In vivo studies of human brain cellular function face challenging ethical and practical difficulties. Animal models are typically used but display distinct cellular differences. One specific example is astrocytes, recently recognized for contribution to neurological diseases and a link to the genetic risk factor apolipoprotein E (APOE). Current astrocytic in vitro models are questioned for lack of biological characterization. Here, we report human induced pluripotent stem cell (hiPSC)-derived astroglia (NES-Astro) developed under defined conditions through long-term neuroepithelial-like stem (ltNES) cells. We characterized NES-Astro and astrocytic models from primary sources, astrocytoma (CCF-STTG1), and hiPSCs through transcriptomics, proteomics, glutamate uptake, inflammatory competence, calcium signaling response, and APOE secretion. Finally, we assess modulation of astrocyte biology using APOE-annotated compounds, confirming hits of the cholesterol biosynthesis pathway in adult and hiPSC-derived astrocytes. Our data show large diversity among astrocytic models and emphasize a cellular context when studying astrocyte biology.
Richard J. Cartwright, Chloe B. Beddingfield, Tom Nordheim
et al.
The five classical Uranian moons are possible ocean worlds that exhibit bizarre geologic landforms, hinting at recent surface-interior communication. However, Uranus' classical moons, as well as its ring moons and irregular satellites, remain poorly understood. We assert that a Flagship-class orbiter is needed to explore the Uranian satellites.
Hniličková H., Hnilička F., Martinková J., Kraus K. (2017): Effects of salt stress on water status, photosynthesis and chlorophyll fluorescence of rocket. Plant Soil Environ., 63: 362–367. Salinity is a significant environmental factor affecting physiological processes in plants. This study monitors the effect of salt stress induced by the NaCl solution (0 – deionized water; 50, 100, 200, 300 mmol/L) in rocket (Eruca sativa (L.) Mill.) cv. Astro over the course of 50 days. Salt stress significantly affected the monitored parameters. The osmotic potential decreased with increasing NaCl concentrations, while relative water content decrease did not take place until 200 mmol/L NaCl. Compared to the control group, transpiration (E) decreased at the concentration of 50 mmol/L NaCl and stomatal conductance (gs) and net photosynthetic rate (Pn) decreased at 100 mmol/L NaCl. Further increase of salt concentrations did not affect Pn and no significant differences gs, E and substomatal concentration CO2 were measured between the concentrations of 200 and 300 mmol/L NaCl. A decrease of Fv/Fm took place from the concentration of 100 mmol/L NaCl, while differences between 200 and 300 mmol/L NaCl were also not significant. The obtained results therefore prove the tolerance of the E. sativa cv. Astro to salt stress.
Patrice Theulé, Christian Endres, Marius Hermanns
et al.
High-resolution gas phase spectroscopy techniques in the microwave, millimeter-wave and terahertz spectral ranges can be used to study complex organic molecules desorbed from interstellar ice analogues surface with a high sensitivity. High-resolution gas phase spectroscopy gives unambiguous information about the molecular composition, the molecular structure, and transition frequencies needed for their detection by radio telescopes in various interstellar and circumstellar environments. The results will be useful not only for interpreting astronomical spectra and understanding astrophysical processes, but also for more general studies of gas-surface chemistry. This paper presents a new experimental approach based on a combination of a chirped-pulse Fourier transform microwave spectrometer detection and a low temperature surface desorption experiment. The experimental set-up is benchmarked on the desorption of ammonia ice detected by high-resolution gas phase microwave spectroscopy.
The effective potential energy of the particles in the field of rotating uniformly magnetized celestial body is investigated. The axis of rotation coincides with the axis of the magnetic field. Electromagnetic field of the body is composed of a dipole magnetic and quadrupole electric fields. The geometry of the trapping regions is studied as a function of the magnetic field magnitude and the rotation speed of the body. Examples of the potential energy topology for different values of these parameters are given. The main difference from the classical Størmer problem is that the single toroidal trapping region predicted by Størmer is divided into equatorial and off-equatorial trapping regions. Applicability of the idealized model of a rotating uniformly magnetized sphere with a vacuum magnetosphere to real celestial bodies is discussed.