Radial velocities and metallicities from infrared Ca II triplet spectroscopy of open clusters II. Berkeley 23, King 1, NGC 559, NGC 6603 and NGC 7245

Context: Open clusters are key to studying the formation and evolution of the Galactic disc. However, there is a deficiency of radial velocity and chemical abundance determinations for open clusters in the literature. Aims: We intend to increase the number of determinations of radial velocities and metallicities from spectroscopy for open clusters. Methods: We acquired medium-resolution spectra (R~8000) in the infrared region Ca II triplet lines (~8500 AA) for several stars in five open clusters with the long-slit IDS spectrograph on the 2.5~m Isaac Newton Telescope (Roque de los Muchachos Observatory, Spain). Radial velocities were obtained by cross-correlation fitting techniques. The relationships available in the literature between the strength of infrared Ca II lines and metallicity were also used to derive the metallicity for each cluster. Results: We obtain = 48.6+/-3.4, -58.4+/-6.8, 26.0+/-4.3 and -65.3+/-3.2 km s-1 for Berkeley 23, NGC 559, NGC 6603 and NGC 7245, respectively. We found [Fe/H] =-0.25+/-0.14 and -0.15+/-0.18 for NGC 559 and NGC 7245, respectively. Berkeley 23 has a low metallicity, [Fe/H] =-0.42+/-0.13, similar to other open clusters in the outskirts of the Galactic disc. In contrast, we derived a high metallicity ([Fe/H] =+0.43+/-0.15) for NGC 6603, which places this system among the most metal rich known open clusters. To our knowledge, this is the first determination of radial velocities and metallicities from spectroscopy for these clusters, except NGC 6603, for which radial velocities had been previously determined. We have also analysed ten stars in the line of sight to King 1. Because of the large dispersion obtained in both radial velocity and metallicity, we cannot be sure that we have sampled true cluster members.Comment: 10 pages, 5 figures, accepted for publication in A&A (minor modifications

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

Simulated Galactic methanol maser distribution to constrain Milky Way parameters

Using trigonometric parallaxes and proper motions of masers associated with massive young stars, the Bar and Spiral Structure Legacy (BeSSeL) survey has reported the most accurate values of the Galactic parameters so far. The determination of these parameters with high accuracy has a widespread impact on Galactic and extragalactic measurements. This research is aimed at establishing the confidence with which such parameters can be determined. This is relevant for the data published in the context of the BeSSeL survey collaboration, but also for future observations, in particular from the Southern Hemisphere. In addition, some astrophysical properties of the masers can be constrained, notably the luminosity function. We have simulated the population of maser-bearing young stars associated with Galactic spiral structure, generating several samples and comparing them with the observed samples used in the BeSSeL survey. Consequently, we checked the determination of Galactic parameters for observational biases introduced by the sample selection. Galactic parameters obtained by the BeSSeL survey do not seem to be biased by the sample selection used. In fact, the published error estimates appear to be conservative for most of the parameters. We show that future BeSSeL data and future observations with Southern arrays will improve the Galactic parameters estimates and smoothly reduce their mutual correlation. Moreover, by modeling future parallax data with larger distance and, thus, greater relative uncertainties for a larger numbers of sources, we found that parallax-distance biasing is an important issue. Hence, using fractional parallax uncertainty in the weighting of the motion data is imperative. Finally, the luminosity function for 6.7 GHz methanol masers was determined, allowing us to estimate the number of Galactic methanol masers.Comment: Accepted for publication in A&A. Language edition include

Finding evolved stars in the inner Galactic disk with Gaia

The Bulge Asymmetries and Dynamical Evolution (BAaDE) survey will provide positions and line-of-sight velocities of ~20,000 evolved, maser bearing stars in the Galactic plane. Although this Galactic region is affected by optical extinction, BAaDE targets may have Gaia cross-matches, eventually providing additional stellar information. In an initial attempt to cross-match BAaDE targets with Gaia, we have found more than 5,000 candidates. Of these, we may expect half to show SiO emission, which will allow us to obtain velocity information. The cross-match is being refined to avoid false positives using different criteria based on distance analysis, flux variability, and color assessment in the mid- and near-IR. Once the cross-matches can be confirmed, we will have a unique sample to characterize the stellar population of evolved stars in the Galactic bulge, which can be considered fossils of the Milky Way formation.Comment: To appear in the Proceedings of the IAU Symposium No. 330: "Astrometry and Astrophysics in the Gaia sky

Enseñanza de Física en el nivel medio : probables estrategias didácticas innovadoras

La dificultad en el aprendizaje de Física es ampliamente conocida en distintos contextos. Ella influye en la eficacia escolar y pone en tela de juicio la calidad educativa de los centros. En este trabajo se describe el estado de avance de una investigación llevada a cabo en IFBA. En la primera etapa de diagnóstico se diseñaron y validaron instrumentos de recolección de información los cuales se aplicaron y están en procesamiento de datos. El producto esperado de esta etapa es una evaluación institucional que evidencie la imagen de la institución respecto a la Física y su enseñanza. En una segunda parte se diseñó e implementó una secuencia didáctica innovadora, sustentada en teorías e investigaciones actuales desarrolladas en el ámbito de didáctica de las ciencias. En ella se está trabajando con dos grupos de estudiantes, uno experimental y otro control. De esta instancia se pretenden obtener conclusiones que evidencien una posible mejora en los resultados del aprendizaje de la Física a partir de modificaciones en las estrategias de enseñanza. La última parte corresponde a la autoevaluación de la propia práctica docente, en esta etapa se validará la secuencia diseñada y su implementación con los instrumentos construidos por el Dr. Godino.A dificuldade na aprendizagem de Física é amplamente conhecida em diferentes contextos. Ela influencia na eficácia escolar e expõe a qualidade educativa dos centros. Neste trabalho se descreve o atual estágio de uma pesquisa que se realiza no IFBA. Na primeira etapa do diagnóstico foram desenhados e validados os instrumentos de recolecção da informação, os quais foram aplicados e estão em processamento de dados. O produto esperado desta etapa é uma avaliação institucional que evidencie a imagem da instituição com respeito à Física y seu ensino. Na segunda parte se elaborou e executou uma sequencia didática inovadora, sustentada em teorias e investigações atuais desenvolvidas no âmbito da didática das ciências. Nela, se está trabalhando com dois grupos de estudantes, um experimental e outro de controle. Desta instancia se pretende obter conclusões que consigam evidenciar uma possível melhora nos resultados da aprendizagem de Física a partir de modificações nas estratégias de ensino. A última parte corresponde à autoavaliação da própria prática docente, e nesta etapa será validada a sequencia desenhada e a sua execução com os instrumentos construídos pelo Dr. Godino da Universidade de Granada

Millimetre spectral indices of transition disks and their relation to the cavity radius

Transition disks are protoplanetary disks with inner depleted dust cavities and excellent candidates to investigate the dust evolution under the existence of a pressure bump. A pressure bump at the outer edge of the cavity allows dust grains from the outer regions to stop their rapid inward migration towards the star and efficiently grow to millimetre sizes. Dynamical interactions with planet(s) have been one of the most exciting theories to explain the clearing of the inner disk. We look for evidence of the presence of millimetre dust particles in transition disks by measuring their spectral index with new and available photometric data. We investigate the influence of the size of the dust depleted cavity on the disk integrated millimetre spectral index. We present the 3mm photometric observations carried out with PdBI of four transition disks: LkHa330, UXTauA, LRLL31, and LRLL67. We use available values of their fluxes at 345GHz to calculate their spectral index, as well as the spectral index for a sample of twenty transition disks. We compare the observations with two kind of models. In the first set of models, we consider coagulation and fragmentation of dust in a disk in which a cavity is formed by a massive planet located at different positions. The second set of models assumes disks with truncated inner parts at different radius and with power-law dust size distributions, where the maximum size of grains is calculated considering turbulence as the source of destructive collisions. We show that the integrated spectral index is higher for transition disks than for regular protoplanetary disks. For transition disks, the probability that the measured spectral index is positively correlated with the cavity radius is 95%. High angular resolution imaging of transition disks is needed to distinguish between the dust trapping scenario and the truncated disk case.Comment: Accepted for publication in A&A, including language editio

Discovery of a Hot Symbiotic Star in the Cold Antarctic Sky: Symbiotics Are Outliers in SkyMapper uvgriz Photometry

Using near-ultraviolet flux excess and variability from the SkyMapper Southern Sky Survey11 as novel diagnostics to search for symbiotic stars?cool giants accreting onto compact objects, typically white dwarfs (WDs), we report that Hen 3-1768 (≡ASAS J195948?8252.7) is a symbiotic star. It may be an optimal target for continuous monitoring by Antarctic telescopes; at a decl. of −82877, it is now the closest known symbiotic to either geographic pole, and the only known symbiotic more southern than the Small Magellanic Cloud (Belczyński et al. 2000; Akras et al. 2019, ApJS, in press). Figure 1 shows that Hen 3-1768 produced unambiguous emission from Raman O vi 6830,7088 Å, He ii 4686 Å, and other transitions, proving that it is a symbiotic star (e.g., Shore et al. 2014). Comparing to Pickles (1998) template spectra, we preliminarily constrained the giant donor´s spectral type to between K4 and K7, making Hen 3-1768 one of the dozen or so yellow symbiotics with stellar-type infrared (IR) colors currently known (e.g., Baella et al. 2016). The 2MASS IR colors (J − H)0 = 0.82 and (H − Ks)0 = 0.21 (Skrutskie et al. 2006; de-reddened by total Galactic extinction12 ) are consistent with this conclusion (see Figure 1 in Baella et al. 2016).Fil: Lucy, Adrian B.. Columbia University; Estados UnidosFil: Sokoloski, J. L.. Columbia University; Estados UnidosFil: Nuñez, Natalia Edith. 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: Wolf, C.. Research School Of Astronomy And Astrophysics, Anu; AustraliaFil: Bohlsen, T.. Mirranook Observatory,; AustraliaFil: Luna, Gerardo Juan Manuel. 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; Argentin

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.