Primeval very low-mass stars and brown dwarfs - VI. Population properties of metal-poor degenerate brown dwarfs

© 2019 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society.We presented 15 new T dwarfs that were selected from UKIRT Infrared Deep Sky Survey, Visible and Infrared Survey Telescope for Astronomy, and Wide-field Infrared Survey Explorer surveys, and confirmed with optical to near infrared spectra obtained with the Very Large Telescope and the Gran Telescopio Canarias. One of these new T dwarfs is mildly metal-poor with slightly suppressed $K$-band flux. We presented a new X-shooter spectrum of a known benchmark sdT5.5 subdwarf, HIP 73786B. To better understand observational properties of brown dwarfs, we discussed transition zones (mass ranges) with low-rate hydrogen, lithium, and deuterium burning in brown dwarf population. The hydrogen burning transition zone is also the substellar transition zone that separates very low-mass stars, transitional, and degenerate brown dwarfs. Transitional brown dwarfs have been discussed in previous works of the Primeval series. Degenerate brown dwarfs without hydrogen fusion are the majority of brown dwarfs. Metal-poor degenerate brown dwarfs of the Galactic thick disc and halo have become T5+ subdwarfs. We selected 41 T5+ subdwarfs from the literature by their suppressed $K$-band flux. We studied the spectral-type - colour correlations, spectral-type - absolute magnitude correlations, colour-colour plots, and HR diagrams of T5+ subdwarfs, in comparison to these of L-T dwarfs and L subdwarfs. We discussed the T5+ subdwarf discovery capability of deep sky surveys in the 2020s.Peer reviewe

ON THE ASSIMILATION OF GNSS PWV MEASUREMENTS IN HEAVY TO TORRENTIAL RAIN EVENTS IN DAVAO CITY, PHILIPPINES

A standalone Global Navigation Satellite System (GNSS) receiver was utilized in this study to get a measure of the atmospheric water vapor in Davao City, Philippines. It aims to monitor the variability of GNSS precipitable water vapor (PWV) especially during heavy to torrential rain. The results of the study showed a positive correlation between GNSS-PWV and precipitation especially in these severe (heavy to torrential) rain events which implies that the assimilation of atmospheric water vapor measurements can improve forecasts of such events

Description of two Enterococcus strains isolated from traditional Peruvian artisanal-produced cheeses with a bacteriocin-like inhibitory activity

The aim of this work was to isolate and to characterize strains of lactic acid bacteria (LAB) with bacteriocin-like inhibitory activity from 27 traditional cheeses artisanal-produced obtained from different Peruvian regions. Twenty Gram+ and catalasenegative strains among 2,277 isolates exhibited bacteriocin-like inhibitory activity against Listeria monocytogenes CWBIB2232 as target strain. No change in inhibitory activity was observed after organic acid neutralization and treatment with catalase of the cell-free supernatant (CFS). The proteinic nature of the antimicrobial activity was confirmed for the twenty LAB strains by proteolytic digestion of the CFS. Two strains, CWBI-B1431 and CWBI-B1430, with the best antimicrobial activity were selected for further researches. These strains were taxonomically identified by phenotypic and genotypic analyses as Enterococcus mundtii (CWBI-B1431) and Enterococcus faecium (CWBI-B1430). The two strains were sensitive to vancomycin (MIC 2 μg.ml-1) and showed absence of haemolysis

The current population of benchmark brown dwarfs

The number of brown dwarfs (BDs) now identified tops 700. Yet our understanding of these cool objects is still lacking, and models are struggling to accurately reproduce observations. What is needed is a method of calibrating the models, BDs whose properties (e.g. age, mass, distance, metallicity) that can be independently determined can provide such calibration. The ability to calculate properties based on observables is set to be of vital importance if we are to be able to measure the properties of fainter, more distant populations of BDs that near-future surveys will reveal, for which ground based spectroscopic studies will become increasingly difficult. We present here the state of the current population of age benchmark brown dwarfs.Comment: 2 pages, 1 figure, to appear in the conference proceedings "New Technologies for Probing the Diversity of Brown Dwarfs and Exoplanets", Shanghai, 19-24 July, 200

Synthesis, resolution, and absolute configuration determination of a vicinal amino alcohol with axial chirality. Application to the synthesis of new box and pybox ligands

New racemic vicinal amino alcohol derivatives with 4-benzylidenecyclohexane skeleton and axial chirality have been prepared. A preparatively easy and efficient protocol for resolution of the N-benzoylamino alcohol is described. Using a 250 x 20 mm (L x ID) Chiralpak (R) IA column, and the appropriate mixture of n-hexane/ethanol/chloroform as eluent, both enantiomers of N-benzoylamino alcohol 3 are obtained with >99% enantiomeric excess (ee) by successive injections of a solution of the racemic sample in chloroform. The obtained axially chiral vicinal amino alcohol is used to synthesize structurally novel bisoxazoline ligands in high yields

Assessment of GNC Impacts of Chemical Plume Impingement in the Case of Prisma Irides Experiment

This paper presents the preliminary analysis of an in-orbit demonstration opportunity to test plume impingement as a viable means to change the attitude state of a space debris based on the Prisma and Picard missions. This technique has been proposed as part of the COBRA concept studied by ESA in collaboration with GMV, Politecnico di Milano and Thales-Alenia Space, as an active debris removal concept relying on the exhaust plume of a monopropellant chemical propulsion system as a means to impart momentum and ultimately modify the orbit of a space debris object in a contactless manner. The feasibility of the experiment is presented as well as its critical areas, no showstoppers are identified

Experimental realization of smectic phase in vortex matter induced by symmetric potentials arranged in two-fold symmetry arrays

Smectic order has been generated in superconducting Nb films with two-fold symmetry arrays of symmetric pinning centers. Magnetic fields applied perpendicularly to the films develop a vortex matter smectic phase that is easily detected when the vortices commensurate with the pinning center array. The smectic phase can be turned on and off with external parameters.Comment: 15 pages, 5 figure

The effect of parallel static and microwave electric fields on excited hydrogen atoms

Motivated by recent experiments we analyse the classical dynamics of a hydrogen atom in parallel static and microwave electric fields. Using an appropriate representation and averaging approximations we show that resonant ionisation is controlled by a separatrix, and provide necessary conditions for a dynamical resonance to affect the ionisation probability. The position of the dynamical resonance is computed using a high-order perturbation series, and estimate its radius of convergence. We show that the position of the dynamical resonance does not coincide precisely with the ionisation maxima, and that the field switch-on time can dramatically affect the ionisation signal which, for long switch times, reflects the shape of an incipient homoclinic. Similarly, the resonance ionisation time can reflect the time-scale of the separatrix motion, which is therefore longer than conventional static field Stark ionisation. We explain why these effects should be observed in the quantum dynamics. PACs: 32.80.Rm, 33.40.+f, 34.10.+x, 05.45.Ac, 05.45.MtComment: 47 pages, 20 figure

Frequency Dependence of Quantum Localization in a Periodically Driven System

We study the quantum localization phenomena for a random matrix model belonging to the Gaussian orthogonal ensemble (GOE). An oscillating external field is applied on the system. After the transient time evolution, energy is saturated to various values depending on the frequencies. We investigate the frequency dependence of the saturated energy. This dependence cannot be explained by a naive picture of successive independent Landau-Zener transitions at avoided level crossing points. The effect of quantum interference is essential. We define the number of Floquet states which have large overlap with the initial state, and calculate its frequency dependence. The number of Floquet states shows approximately linear dependence on the frequency, when the frequency is small. Comparing the localization length in Floquet states and that in energy states from the viewpoint of the Anderson localization, we conclude that the Landau-Zener picture works for the local transition processes between levels.Comment: 12 pages and 6 figure