The Be-test in the Li-rich star \#1657 of NGC 6397: evidence for Li-flash in RGB stars?

The Li-rich turn-off star in the globular cluster NGC 6397 could represent the smoking gun for some very rare episode of Li enrichment in globular clusters. We aim to understand the nature of the Li enrichment by performing a spectroscopic analysis of the star, in particular of its beryllium (Be) abundance, and by investigating its binary nature. We observe the near UV region where the Beii resonance doublet and the NH bands are located. We could not detect the Beii lines and derive an upper limit of log (Be/H)< -12.2, that is consistent with the Be observed in other stars of the cluster. We could detect a weak G-band, which implies a mild carbon enhancement [C/Fe]$+0.4\pm0.2$. We could not detect the UV NH band, and we derive an upper limit [N/Fe]$< 0.0$. For oxygen we could notdetect any of the near UV OH lines, which implies that oxygen cannot be strongly enhanced in this star. This is consistent with the detection of the Oi triplet at 777nm, which is consistent with [O/Fe]~0.5. Combining the UVES and Mike data, we could not detect any variation in the radial velocity greater than 0.95 kms$^{-1}$ over 8 years. The chemical composition of the star strongly resembles that of `first generation' NGC6397 stars, with the huge Li as the only deviating abundance. Not detecting Be rules out two possible explanations of the Li overabundance: capture of a substellar body and spallation caused by a nearby type II SNe. Discrepancies are also found with respect to other accretion scenarios,except for contamination by the ejecta of a star that has undergone the RGB Li-flash.Comment: Accepted for publication in A&

Capital structure and its determinants in the United Kingdom – a decompositional analysis

Prior research on capital structure by Rajan and Zingales (1995) suggests that the level of gearing in UK companies is positively related to size and tangibility, and negatively correlated with profitability and the level of growth opportunities. However, as argued by Harris and Raviv (1991), 'The interpretation of results must be tempered by an awareness of the difficulties involved in measuring both leverage and the explanatory variables of interest'. In this study the focus is on the difficulties of measuring gearing, and the sensitivity of Rajan and Zingales' results to variations in gearing measures are tested. Based on an analysis of the capital structure of 822 UK companies, Rajan and Zingales' results are found to be highly definitional-dependent. The determinants of gearing appear to vary significantly, depending upon which component of debt is being analysed. In particular, significant differences are found in the determinants of long- and short-term forms of debt. Given that trade credit and equivalent, on average, accounts for more than 62% of total debt, the results are particularly sensitive to whether such debt is included in the gearing measure. It is argued, therefore, that analysis of capital structure is incomplete without a detailed examination of all forms of corporate debt

Making SPIFFI SPIFFIER: Upgrade of the SPIFFI instrument for use in ERIS and performance analysis from re-commissioning

SPIFFI is an AO-fed integral field spectrograph operating as part of SINFONI on the VLT, which will be upgraded and reused as SPIFFIER in the new VLT instrument ERIS. In January 2016, we used new technology developments to perform an early upgrade to optical subsystems in the SPIFFI instrument so ongoing scientific programs can make use of enhanced performance before ERIS arrives in 2020. We report on the upgraded components and the performance of SPIFFI after the upgrade, including gains in throughput and spatial and spectral resolution. We show results from re-commissioning, highlighting the potential for scientific programs to use the capabilities of the upgraded SPIFFI. Finally, we discuss the additional upgrades for SPIFFIER which will be implemented before it is integrated into ERIS.Comment: 20 pages, 12 figures. Proceedings from SPIE Astronomical Telescopes and Instrumentation 201

The Gaia-ESO survey : Processing FLAMES-UVES spectra

Date of Acceptance: 19/03/2014The Gaia-ESO Survey is a large public spectroscopic survey that aims to derive radial velocities and fundamental parameters of about 105 Milky Way stars in the field and in clusters. Observations are carried out with the multi-object optical spectrograph FLAMES, using simultaneously the medium-resolution (R ~ 20 000) GIRAFFE spectrograph and the high-resolution (R ~ 47 000) UVES spectrograph. In this paper we describe the methods and the software used for the data reduction, the derivation of the radial velocities, and the quality control of the FLAMES-UVES spectra. Data reduction has been performed using a workflow specifically developed for this project. This workflow runs the ESO public pipeline optimizing the data reduction for the Gaia-ESO Survey, automatically performs sky subtraction, barycentric correction and normalisation, and calculates radial velocities and a first guess of the rotational velocities. The quality control is performed using the output parameters from the ESO pipeline, by a visual inspection of the spectra and by the analysis of the signal-to-noise ratio of the spectra. Using the observations of the first 18 months, specifically targets observed multiple times at different epochs, stars observed with both GIRAFFE and UVES, and observations of radial velocity standards, we estimated the precision and the accuracy of the radial velocities. The statistical error on the radial velocities is σ ~ 0.4 km s-1 and is mainly due to uncertainties in the zero point of the wavelength calibration. However, we found a systematic bias with respect to the GIRAFFE spectra (~0.9 km s-1) and to the radial velocities of the standard stars (~0.5 km s-1) retrieved from the literature. This bias will be corrected in the future data releases, when a common zero point for all the set-ups and instruments used for the survey is be established.Peer reviewe

Three-dimensional distribution of ejecta in Supernova 1987A at 10 000 days

Due to its proximity, SN 1987A offers a unique opportunity to directly observe the geometry of a stellar explosion as it unfolds. Here we present spectral and imaging observations of SN 1987A obtained ~10,000 days after the explosion with HST/STIS and VLT/SINFONI at optical and near-infrared wavelengths. These observations allow us to produce the most detailed 3D map of H-alpha to date, the first 3D maps for [Ca II] \lambda \lambda 7292, 7324, [O I] \lambda \lambda 6300, 6364 and Mg II \lambda \lambda 9218, 9244, as well as new maps for [Si I]+[Fe II] 1.644 \mu m and He I 2.058 \mu m. A comparison with previous observations shows that the [Si I]+[Fe II] flux and morphology have not changed significantly during the past ten years, providing evidence that it is powered by 44Ti. The time-evolution of H-alpha shows that it is predominantly powered by X-rays from the ring, in agreement with previous findings. All lines that have sufficient signal show a similar large-scale 3D structure, with a north-south asymmetry that resembles a broken dipole. This structure correlates with early observations of asymmetries, showing that there is a global asymmetry that extends from the inner core to the outer envelope. On smaller scales, the two brightest lines, H-alpha and [Si I]+[Fe II] 1.644 \mu m, show substructures at the level of ~ 200 - 1000 km/s and clear differences in their 3D geometries. We discuss these results in the context of explosion models and the properties of dust in the ejecta.Comment: Accepted for publication in Ap

Debt Policy and Economic Growth in a Small Open Economy Model with Productive Government Spending

In this paper, we examine the effects of introducing constraints on government borrowing using a continuous-time overlapping generations model of a small open economy. We consider government placing constraints on the amount of government bonds outstanding by establishing an upper limit, or target level, for the ratio of government bonds to gross domestic product. We first show that there exist multiple steady states in the model small open economy. One is a steady state with high growth, the other a steady state with low growth. We next examine how changes in the target level for bonds affect economic growth rates at the steady states. If the economy has a positive amount of asset holdings, we obtain the following results. When the government runs budget surpluses, an increase in the target level for government bonds reduces the growth rate of the low-growth economy, but raises the growth rate of the high-growth economy. However, when the government runs budget deficits, an increase in the target level for government bonds raises the growth rate of the low-growth economy, but reduces the growth rate of the high-growth economy. If the economy has a negative amount of asset holdings, the results are ambiguous

Comparative interactomics analysis of different ALS-associated proteins identifies converging molecular pathways

Amyotrophic lateral sclerosis (ALS) is a devastating neurological disease with no effective treatment available. An increasing number of genetic causes of ALS are being identified, but how these genetic defects lead to motor neuron degeneration and to which extent they affect common cellular pathways remains incompletely understood. To address these questions, we performed an interactomic analysis to identify binding partners of wild-type (WT) and ALS-associated mutant versions of ATXN2, C9orf72, FUS, OPTN, TDP-43 and UBQLN2 in neuronal cells. This analysis identified several known but also many novel binding partners of these proteins

Peculiarities of selecting the gearboxes and wheel shift coefficients in the optimization of drive gear transmissions

В якості вузлового моменту оптимізаційного проектування тягових зубчастих передач залізничного рухомого складу виділено процедуру обґрунтованого вибору коефіцієнтів зміщення шестерень і коліс за рахунок використання відповідних блокувальних контурів. Обґрунтовано актуальність досліджень з розроблення методичного забезпечення для раціонального отримання блокувальних контурів при проектуванні тягових зубастих передач. Представлені розроблені математичні залежності, що пов’язують фіксовані величині обмежувальних і контрольованих параметрів передач з числами зубців і коефіцієнтами зміщення шестерні та колеса. Їх використання дозволяє отримувати конкретні блокувальні контури для вибору коефіцієнтів зміщення шестерні та колеса при оптимізаційному проектуванні тягових зубчастих передач з різними початковими параметрами. Наведено приклад практичної реалізації розроблених математичних залежностей при отриманні блокувального контуру для вибору коефіцієнтів зміщення шестерні та колеса тягової зубчастої передачі сучасного магістрального вантажного тепловозу. Зроблено висновок про доцільність використання запропонованого методичного забезпечення при оптимізаційному проектуванні тягових зубчатих передач.As a key point in the optimization design of traction gears of the railway rolling stock, a procedure for a reasonable choice of the coefficients for the displacement of gears and wheels is provided by using the appropriate blocking circuits. The relevance of studies on the development of methodological support for the rational production of blocking contours in the design of traction-toothed gears is substantiated. The developed mathematical dependences connecting the fixed values of the limiting and controlled parameters of the gears with the numbers of the teeth and the gearing coefficients of the gears and wheels are presented. Their use makes it possible to obtain specific blocking contours for the selection of gear and wheel bias coefficients in the optimization design of traction gears with different initial parameters. An example of the practical implementation of the developed mathematical dependencies in obtaining a blocking contour for selecting the gear displacement coefficients and the traction gear wheel of a modern mainline freight locomotive is given. The conclusion is made about the expediency of using the proposed methodological support in the optimization design of traction gears