Symbiotic stars in X-rays II: faint sources detected with XMM-Newton and Chandra

We report the detection, with ${\it Chandra}$ and XMM-${\it Newton}$, of faint, soft X-ray emission from four symbiotics stars that were not known to be X-ray sources. These four object show a $\beta$-type X-ray spectrum, i.e. their spectra can be modeled with an absorbed optically thin thermal emission with temperatures of a few million degrees. Photometric series obtained with the Optical Monitor on board XMM-${\it Newton}$ from V2416 Sgr and NSV 25735 support the proposed scenario where the X-ray emission is produced in a shock-heated region inside the symbiotic nebulae.Comment: 5 pages, 1 figure, 2 tables; A&A publishe

Symbiotic stars in X-rays III: Suzaku observations

We describe the X-ray emission as observed with Suzaku from five symbiotic stars that we selected for deep Suzaku observations after their initial detection with ROSAT, ASCA and Swift. We find that the X-ray spectra of all five sources can be adequately fit with absorbed, optically thin thermal plasma models, with either single- or multi-temperature plasmas. These models are compatible with the X-ray emission originating in the boundary layer between an accretion disk and a white dwarf. The high plasma temperatures of kT$~>3$ keV for all five targets were greater than expected for colliding winds. Based on these high temperatures, as well as previous measurements of UV variability and UV luminosity, and the large amplitude of X-ray flickering in 4 Dra, we conclude that all five sources are accretion-powered through predominantly optically thick boundary layers. Our X-ray data allow us to observe a small, optically thin portion of the emission from these boundary layers. Given the time between previous observations and these observations, we find that the intrinsic X-ray flux and the intervening absorbing column can vary by factors of three or more on a time scale of years. However, the location of the absorber and the relationship between changes in accretion rate and absorption are still elusive.Comment: 14 pages, 3 figures and 3 tables. Accepted to published 04/15/2016. arXiv admin note: substantial text overlap with arXiv:1505.0063

Determination of transition frequencies in a single 138^{138}Ba+^{+} ion

Transition frequencies between low-lying energy levels in a single trapped $^{138}$Ba$^{+}$ ion have been measured with laser spectroscopy referenced to an optical frequency comb. By extracting the frequencies of one-photon and two-photon components of the line shape using an eight-level optical Bloch model, we achieved 0.1 MHz accuracy for the 5d $^{2}$D$_{3/2}$ - 6p $^{2}$P$_{1/2}$ and 6s $^{2}$S$_{1/2}$ - 5d $^{2}$D$_{3/2}$ transition frequencies, and 0.2 MHz for the 6s $^{2}$S$_{1/2}$ - 6p $^{2}$P$_{1/2}$ transition frequency.Comment: 5 pages, 7 figures, submitted to Phys. Rev.

Duality symmetric massive type II theories in D=8 and D=6

We study $T^2$ compactification of massive type IIA supergravity in presence of possible Ramond-Ramond (RR) background fluxes. The resulting theory in D=8 is shown to possess full $SL(2,R)\times SL(2,R)$ T-duality symmetry similar to the massless case. It is shown that elements of duality symmetry interpolate between massive type IIA compactified on $T^2$ and ordinary type IIA compactified on $T^2$ with RR 2-form flux. We also discuss relationship between M-theory vacua and massive type IIA vacua. The D8-brane is found to correspond to M-theory `pure gravity' solution which is a direct product of 7-dimensional Minkowski space and a 4-dimensional instanton. We also construct D6-D8 bound state which preserves 1/2 supersymmetries. We then discuss massive IIA compactification on $T^4$ and point out that when all possible RR fluxes on $T^4$ are turned on the six-dimensional theory appears to assume a nice SO(4,4) invariant form.Comment: 19 pages, JHEP3, typos fixed, references added; v2: small correction in eq.(5.3), published in JHE

Rotating membranes on G_2 manifolds, logarithmic anomalous dimensions and N=1 duality

We show that the $E-S \sim \log S$ behaviour found for long strings rotating on $AdS_5\times S^5$ may be reproduced by membranes rotating on $AdS_4\times S^7$ and on a warped $AdS_5$ M-theory solution. We go on to obtain rotating membrane configurations with the same $E-K \sim \log K$ relation on $G_2$ holonomy backgrounds that are dual to ${\mathcal{N}}=1$ gauge theories in four dimensions. We study membrane configurations on $G_2$ holonomy backgrounds systematically, finding various other Energy-Charge relations. We end with some comments about strings rotating on warped backgrounds.Comment: 1+44 pages. Latex. No figures. Minor corrections to make all membrane configurations consistent. One configuration is now noncompac

New Superhard Phases for 3D C60-based Fullerites

We have explored new possible phases of 3D C60-based fullerites using semiempirical potentials and ab-initio density functional methods. We have found three closely related structures - two body centered orthorhombic and one body centered cubic - having 52, 56 and 60 tetracoordinated atoms per molecule. These 3D polymers result in semiconductors with bulk moduli near 300 GPa, and shear moduli around 240 GPa, which make them good candidates for new low density superhard materials.Comment: To be published in Physical Review Letter

Does the current taxonomic delimitation of Galianthe find support in phylogenetic perspective?

Galianthe Griseb. is a neotropical genus comprising 50 species divided into two subgenera: G. subgen. Galianthe (41 spp.), characterized by homogeneous morphological traits, with species further divided into two sections (G. secc. Galianthe and G. secc. Laxae); and G. subgen. Ebelia (14 spp.) with more heterogeneous morphological characteristics. Due to its morphological similarity with other genera, Galianthe has historically been associated with Borreria, Spermacoce, Diodia (based on fruit type), as well as Denscantia and Emmeorhiza (based on inflorescence type). In recent years, molecular studies have established Galianthe as a basal genus within the Spermacoce clade, closely related to other genera such as Carajasia and Schwendenera. Despite the progress made in recent molecular studies, the studies have focused on a limited number of species within the genus, failing to encompass all infrageneric categories. Questioning of the current taxonomic delimitation of the genus, this study aims to test the monophyly of Galianthe and explore its infrageneric and interspecific phylogenetic relationships. Three markers (two nuclear: ITS, ETS, and one plastid: rps16) were utilized, encompassing 107 entities, including 42 Galianthe species, thereby representing 76% of the current genus diversity, as well as 17 closely related genera within the Spermacoce clade. The phylogenetic results confirm the monophyly of Galianthe, revealing the presence of three major subclades. Subclades I and II comprise several G. subgen. Ebelia species, whereas subclade III consists of all G. subgen. Galianthe species plus G. angulata. Regarding the sections, monophyly was not supported. Based on these findings, it can be concluded that G. subgen. Ebelia is paraphyletic, G. subgen. Galianthe is potentially paraphyletic due to G. angulata, and there is no clear distinction between the sections

Efecto de la aplicación de herbicidas sobre la calidad comercial e industrial de trigo pan

Se trató de verificar la incidencia de los herbicidas Bromoxinil, 2.4-D más Piclorán y 2,4-D más Dicamba a dosis normal y doble aplicadas en cinco épocas (entre cinco hojas y aristas asomando~ sobre la calidad comercial e industrial de trigo de ciclo largo Cv. Chasicó INTA. No se encontraron diferencias en peso de mil granos (PMG) Y peso hectolítrico (PH) en ningún caso. El porcentaje de extracción de harina (EP) mostró diferencias significativas debido a la época. El tenor de proteína cruda de la harina fue modificado por el tipo de herbicida más que por la dosis, la época de aplicación no produjo efecto significativo. El trabajo de deformación (W) fue afectado significativamente por la dosis, no así por el tipo de herbicida y época de aplicación. El índice de estabilidad (P/G) presentó diferencias significativas debido a los tres factores (tipo, dosis y época). Se detectó interacción dosis por época para éste parámetro. Comparados con el desmalezado manual Bromoxinil se produjo efectos significativos sobre la cantidad y calidad de la proteína de la harina, mientras que los mayores efectos fueron producidos por 2,4-D más Dicamba. Las variaciones de rendimiento explican en parte las diferencias en el contenido de proteínas.Directores: Ings. Agrs. F. D. García y O. J. Rubiol

ζ1 + ζ2 Reticuli binary system: a puzzling chromospheric activity pattern

We perform, for the first time, a detailed long-term activity study of the binary system ζ Ret. We use all available HARPS spectra obtained between the years 2003 and 2016. We build a time series of the Mount Wilson S index for both stars, then we analyse these series by using Lomb-Scargle periodograms. The components ζ1 Ret and ζ2 Ret that belong to this binary system are physically very similar to each other and also similar to our Sun, which makes it a remarkable system. We detect in the solar-analogue star ζ2 Ret a long-term activity cycle with a period of ?10 yr, similar to the solar one (?11 yr). It is worthwhile to mention that this object satisfies previous criteria for a flat star and for a cycling star simultaneously. Another interesting feature of this binary system is a high ?0.220 dex difference between the average log (R^´ }_HK) activity levels of both stars. Our study clearly shows that ζ1 Ret is significantly more active than ζ2 Ret. In addition, ζ1 Ret shows an erratic variability in its stellar activity. In this work, we explore different scenarios trying to explain this rare behaviour in a pair of coeval stars, which could help to explain the difference in this and other binary systems. From these results, we also warn that for the development of activity-age calibrations (which commonly use binary systems and/or stellar clusters as calibrators) the whole history of activity available for the stars involved should be taken into account.Fil: Flores, M. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Saffe, Carlos. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Buccino, Andrea Paola. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Jaque Arancibia, Marcelo Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: González, J F. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Nuñez, N E. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio. Universidad Nacional de San Juan. Instituto de Ciencias Astronómicas, de la Tierra y del Espacio; ArgentinaFil: Jofré, E. Universidad Nacional de Córdoba. Observatorio Astronómico de Córdoba; Argentin