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

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

The contribution of Chinese exports to climate change

Within 5 years, China's CO2 emissions have nearly doubled, and China may already be the world's largest emitter of CO2. Evidence suggests that exports could be a main cause for the rise in Chinese CO2 emissions; however, no systematic study has analyzed this issue, especially over time. We find that in 2005, around one-third of Chinese emissions (1700 Mt CO2) were due to production of exports, and this proportion has risen from 12% (230 Mt) in 1987 and only 21% (760 Mt) as recently as 2002. It is likely that consumption in the developed world is driving this trend. A majority of these emissions have largely escaped the scrutiny of arguments over “carbon leakage” due to the current, narrow definition of leakage. Climate policies which would make the developed world responsible for China's export emissions have both benefits and costs, and must be carefully designed to achieve political consensus and equity. Whoever is responsible for these emissions, China's rapidly expanding infrastructure and inefficient coal-powered electricity system need urgent attention

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

The role of credit ratings on capital structure and its speed of adjustment: an international study

Using an international dataset, we examine the role of issuers’ credit ratings in explaining corporate leverage and the speed with which firms adjust toward their optimal level of leverage. We find that, in countries with a more market-oriented financial system, the impact of credit ratings on firms’ capital structure is more significant and that firms with a poorer credit rating adjust more rapidly. Furthermore, our results show some striking differences in the speed of adjusting capital structure between firms rated as speculative and investment grade, with the former adjusting much more rapidly. As hypothesized, those differences are statistically significant only for firms based in a more market-oriented economy

Capital structure revisited. Do crisis and competition matter in a Keiretsu corporate structure?

The file attached to this record is the author's final peer reviewed version.open accessWe investigate firm-level determinants of capital structure using a large sample of 4,284 Japanese firms over a nineteen-year period (i.e., over 61,000 firm-year observations), a hitherto less examined sample for this purpose. We conduct our analysis and interpret our findings predominantly within the pecking order, the trade-off and the agency theoretical frameworks. We uncover three new findings. First, our evidence indicates that insights derived from the extant literature on capital structure are cross-national and are applicable in the context of Japan, despite the unique characteristics of Japanese firms. Second, financial crisis significantly impacts the relationship between leverage and firm-level determinants, particularly accentuating the effect of asset tangibility and growth. Third, product market competition significantly impacts the observed relationship between firm-level determinants and leverage. Our results are robust, controlling for the joint effects of competition and crisis

Nebular and global properties of the gravitationally lensed galaxy "the 8 o'clock arc"

We present the analysis of new NIR, intermediate-resolution spectra of the gravitationally lensed galaxy "the 8 o'clock arc" at z_sys = 2.7350 obtained with VLT/X-shooter. These rest-frame optical data, combined with HST and Spitzer images, provide very valuable information, which nicely complement our previous detailed rest-frame UV spectral analysis. From high-resolution HST images, we reconstruct the morphology of the arc in the source plane, and identify that the source is formed of two majors parts, the main galaxy component and a smaller blob separated by 1.2 kpc in projected distance. The blob, with a twice larger magnification factor, is resolved in the spectra. The multi-Gaussian fitting of detected nebular emission lines and the spectral energy distribution modeling of the available multi-wavelength photometry provide the census of gaseous and stellar dust extinctions, gas-phase metallicities, star-formation rates (SFRs), and stellar, gas, and dynamical masses for both the main galaxy and the blob. As a result, the 8 o'clock arc shows a marginal trend for a more attenuated ionized gas than stars, and supports a dependence of the dust properties on the SFR. With a high specific star-formation rate, SSFR = 33+/-19 Gyr^{-1}, this lensed Lyman-break galaxy deviates from the mass-SFR relation, and is characterized by a young age of 40^{+25}_{-20} Myr and a high gas fraction of about 72%. The 8 o'clock arc satisfies the fundamental mass, SFR, and metallicity relation, and favors that it holds up beyond z~2.5. We believe that the blob, with a gas mass M_gas = (2.2+/-0.9)x10^{9} Msun (one order of magnitude lower than the mass of the galaxy), a half-light radius r1/2 = 0.53+/-0.05 kpc, a star-formation rate SFR_Halpha = 33+/-19 Msun yr^{-1}, and in rotation around the main core of the galaxy, is one of these star-forming clumps commonly observed in z>1 star-forming galaxies. (Abridged)Comment: 15 pages, 5 figures, published in Astronomy and Astrophysic

Massive Stars In The W33 Giant Molecular Complex

Rich in H II regions, giant molecular clouds are natural laboratories to study massive stars and sequential star formation. The Galactic star-forming complex W33 is located at = ∼ ◦ l 12.8 and at a distance of 2.4 kpc and has a size of ≈10 pc and a total mass of ≈(0.8−8.0) × 105 M⊙. The integrated radio and IR luminosity of W33—when combined with the direct detection of methanol masers, the protostellar object W33A, and the protocluster embedded within the radio source W33 main—mark the region as a site of vigorous ongoing star formation. In order to assess the long-term star formation history, we performed an infrared spectroscopic search for massive stars, detecting for the first time 14 early-type stars, including one WN6 star and four O4–7 stars. The distribution of spectral types suggests that this population formed during the past ∼2–4 Myr, while the absence of red supergiants precludes extensive star formation at ages 6–30 Myr. This activity appears distributed throughout the region and does not appear to have yielded the dense stellar clusters that characterize other star-forming complexes such as Carina and G305. Instead, we anticipate that W33 will eventually evolve into a loose stellar aggregate, with Cyg OB2 serving as a useful, albeit richer and more massive, comparator. Given recent distance estimates, and despite a remarkably similar stellar population, the rich cluster Cl 1813–178 located on the northwest edge of W33 does not appear to be physically associated with W33