Chandra and Suzaku observations of the Be/X-ray star HD110432

We present an analysis of a pointed 141 ks Chandra high-resolution transmission gratings observation of the Be X-ray emitting star HD110432, a prominent member of the γ Cas analogs. This observation represents the first high-resolution spectrum taken for this source as well as the longest uninterrupted observation of any γ Cas analog. The Chandra light curve shows a high variability but its analysis fails to detect any coherent periodicity up to a frequency of 0.05 Hz. Hardness ratio versus intensity analyses demonstrate that the relative contributions of the [1.5-3] Å, [3-6] Å, and [6-16] Å energy bands to the total flux change rapidly in the short term. The analysis of the Chandra High Energy Transmission Grating (HETG) spectrum shows that, to correctly describe the spectrum, three model components are needed. Two of those components are optically thin thermal plasmas of different temperatures (kT ≈ 8-9 and 0.2-0.3 keV, respectively) described by the models vmekal or bvapec. The Fe abundance in each of these two components appears equal within the errors and is slightly subsolar with Z ≈ 0.75 Z ☉. The bvapec model better describes the Fe L transitions, although it cannot fit well the Na XI Lyα line at 10.02 Å, which appears to be overabundant. Two different models seem to describe well the third component. One possibility is a third hot optically thin thermal plasma at kT = 16-21 keV with an Fe abundance Z ≈ 0.3 Z ☉, definitely smaller than for the other two thermal components. Furthermore, the bvapec model describes well the Fe K shell transitions because it accounts for the turbulence broadening of the Fe XXV and Fe XXVI lines with a v turb ≈ 1200 km s–1. These two lines, contributed mainly by the hot thermal plasma, are significantly wider than the Fe Kα line whose FWHM < 5 mÅ is not resolved by Chandra. Alternatively, the third component can be described by a power law with a photon index of Γ = 1.56. In either case, the Chandra HETG spectrum establishes that each one of these components must be modified by distinct absorption columns. The analysis of a noncontemporaneous 25 ks Suzaku observation shows the presence of a hard tail extending up to at least 33 keV. The Suzaku spectrum is described with the sum of two components: an optically thin thermal plasma at kT ≈ 9 keV and Z ≈ 0.74 Z ☉, and a very hot second plasma with kT ≈ 33 keV or, alternatively, a power law with photon index of Γ = 1.58. In either case, each one of the two components must be affected by different absorption columns. Therefore, the kT = 8-9 keV component is definitely needed while the nature of the harder emission cannot be unambiguously established with the present data sets. The analysis of the Si XIII and S XV He-like triplets present in the Chandra spectrum points to a very dense (ne ~ 1013 cm–3) plasma located either close to the stellar surface (r < 3R *) of the Be star or, alternatively, very close (r ~ 1.5R WD) to the surface of a (hypothetical) white dwarf companion. We argue, however, that the available data support the first scenario.

Accreting magnetars: a new type of high-mass X-ray binaries?

The discovery of very slow pulsations (Pspin =5560 s) has solved the long-standing question of the nature of the compact object in the high-mass X-ray binary 4U 2206+54 but has posed new ones. According to spin evolutionary models in close binary systems, such slow pulsations require a neutron star magnetic field strength larger than the quantum critical value of 4.4 × 1013 G, suggesting the presence of a magnetar. We present the first XMM–Newton observations of 4U 2206+54 and investigate its spin evolution. We find that the observed spin-down rate agrees with the magnetar scenario. We analyse Integral Spacecraft Gamma-Ray Imager (ISGRI)/INTErnational Gamma-RAy Laboratory (INTEGRAL) observations of 4U 2206+54 to search for the previously suggested cyclotron resonance scattering feature at ∼30 keV. We do not find a clear indication of the presence of the line, although certain spectra display shallow dips, not always at 30 keV. The association of these dips with a cyclotron line is very dubious because of its apparent transient nature. We also investigate the energy spectrum of 4U 2206+54 in the energy range 0.3–10 keV with unprecedented detail and report for the first time the detection of very weak 6.5 keV fluorescence iron lines. The photoelectric absorption is consistent with the interstellar value, indicating very small amount of local matter, which would explain the weakness of the florescence lines. The lack of matter locally to the source may be the consequence of the relatively large orbital separation of the two components of the binary. The wind would be too tenuous in the vicinity of the neutron star.

Astrophysical parameters of the peculiar X-ray transient IGR J11215−5952

Context. The current generation of X-ray satellites has discovered many new X-ray sources that are difficult to classify within the well-described subclasses. The hard X-ray source IGR J11215−5952 is a peculiar transient, displaying very short X-ray outbursts every 165 days. Aims. To characterise the source, we obtained high-resolution spectra of the optical counterpart, HD 306414, at different epochs, spanning a total of three months, before and around the 2007 February outburst with the combined aims of deriving its astrophysical parameters and searching for orbital modulation. Methods. We fit model atmospheres generated with the fastwind code to the spectrum, and used the interstellar lines in the spectrum to estimate its distance. We also cross-correlated each individual spectrum to the best-fit model to derive radial velocities. Results. From its spectral features, we classify HD 306414 as B0.5 Ia. From the model fit, we find Teff ≈ 24 700 K and log g ≈ 2.7, in good agreement with the morphological classification. Using the interstellar lines in its spectrum, we estimate a distance to HD 306414 d ≳ 7 kpc. Assuming this distance, we derive R∗ ≈ 40 R⊙ and Mspect ≈ 30 M⊙ (consistent, within errors, with Mevol ≈ 38 M⊙, and in good agreement with calibrations for the spectral type). Analysis of the radial velocity curve reveals that radial velocity changes are not dominated by the orbital motion, and provide an upper limit on the semi-amplitude for the optical component Kopt ≲ 11 ± 6 km   s-1. Large variations in the depth and shape of photospheric lines suggest the presence of strong pulsations, which may be the main cause of the radial velocity changes. Very significant variations, uncorrelated with those of the photospheric lines are seen in the shape and position of the Hα emission feature around the time of the X-ray outburst, but large excursions are also observed at other times. Conclusions. HD 306414 is a normal B0.5 Ia supergiant. Its radial velocity curve is dominated by an effect that is different from binary motion, and is most likely stellar pulsations. The data available suggest that the X-ray outbursts are caused by the close passage of the neutron star in a very eccentric orbit, perhaps leading to localised mass outflow.

O mercado da arte moderna e contemporânea em Portugal : 2005-2013

Tese de doutoramento, História (História de Arte), Universidade de Lisboa, Faculdade de Letras, 2016

Designing a Genuine EMU: Which "Unions" for EU and Eurozone? Bruges European Economic Policy (BEEP) Briefing 34/2014

The initial ‘framing’ (in the summer of 2012) of the ‘genuine EMU’ for the wider public suggested to design an entire series of ‘unions’. So many ‘unions’ are neither necessary nor desirable – only some are and their design matters. The paper critically discusses first the negative fall-out of the crisis for EMU, and subsequently assesses the fiscal and the banking unions as accomplished so far, without going into highly specific technical details. The assessment is moderately positive, although there is ample scope for further improvement and a risk for short-term turbulence once the ECB has finished its tests and reviews. What about the parade of other ’unions’ such as economic union, social union and political union? The macro-economic imbalances procedure (MIP) and possibly the ESRB have overcome the pre-crisis disregard of macro competitiveness. The three components of ‘economic union’ (single market, economic policy coordination and budgetary disciplines) have all been strengthened. The last two ‘unions’, on the other hand, would imply a fundamental change in the conferral of powers to the EU/ Eurozone, with drastic and possibly very serious long-run implications, including a break-up of the Union, if such proposals would be pushed through. The cure is worse than the disease. Whereas social union is perhaps easier to dismiss as a ‘misfit’ in the EU, the recent popularity of suggesting a ‘political union’ is seen as worrisome. Probably, nobody knows what a ‘political union’ is, or, at best, it is a highly elastic notion: it might be thought necessary for reasons of domestic economic reforms in EU countries, for a larger common budget, for some EU tax power, for (greater) risk pooling, for ‘symmetric’ macro-economic adjustment and for some ultimate control of the ECB in times of crisis. Taking each one of these arguments separately, a range of more typical EU solutions might be found without suggesting a ‘political union’. Just as ‘fiscal capacity’ was long an all-or-nothing taboo for shifting bank resolution to the EU level, now solved with a modest common Fund and carefully confined but centralised powers, the author suggests that other carefully targeted responses can be designed for the various aspects where seen as indispensable, including the political say of a lender-of-last-resort function of the ECB. Hence, neither a social nor a political union worthy of the name ought to be pursued. Yet, political legitimacy matters, both with national parliaments and the grassroots. National parliaments will have to play a larger role.

Determinants of Growth and Inflation in Southern Mediterranean Countries. MEDPRO Technical Report No. 10/March 2012

Despite significant economic reforms in many Southern Mediterranean EU neighbour countries, their growth performance has on average been subdued. This study analyses the differences in growth performance and macroeconomic stability across Mediterranean countries, to draw lessons for the future. The main findings are that Southern Mediterranean countries should benefit from closer ties with the EU that result in higher levels of trade and FDI inflows, once the turbulence of the ‘Arab Spring’ is resolved, and from the development of financial markets and infrastructure. They will also benefit in keeping inflation under control, which will depend in great part on their ability to maintain fiscal discipline and sustainable current accounts. One of the main challenges for the region will be to implement structural reforms that can help them absorb a large pool of unemployed without creating upward risks to inflation.

Monetary policy and the over-investment cycle: China as an extreme case. CEPS Commentary, 27 August 2015

Against the background of the severe turbulence that is hitting global stock markets, Daniel Gros examines the looming slowdown in the Chinese economy in this CEPS Commentary, which he attributes to an underlying ‘real’ domestic investment/savings imbalance. Given the magnitude of this imbalance, Gros thinks it is unlikely to be solved by monetary policy and that the best that can be hoped for is that the central banks will manage to ‘paper over’ some of the unavoidable symptoms in credit markets.

What direction for Turkey? A plea for political reconciliation. EPIN Commentary No. 26/14 October 2015

Even before the recent terrorist attacks in Ankara, Turkey was a country in crisis. In this EPIN Commentary Umut Uzer attempts to shed light on the political turbulence and increasing polarisation in the country, and makes a plea for a return to consensus-building ahead of the fresh round of elections in November. The author also calls upon the EU to offer incentives to Turkey to continue on the path of EU membership, but if membership is out of the question, then other platforms for cooperation should be negotiated. The EU should speak in a candid manner and make clear what kind of future relationship it envisages for Turkey, because now, more than ever, cooperation is in both their interests.

Economic Policy Coordination in the Euro Area under the European Semester. CEPS Special Report No. 123, December 2015

The implementation record of the Country Specific Recommendations (CSRs) has declined over time, as financial turbulence lessened and the economic outlook started to improve. Urgency for reforms seemingly receded to leave room to request member states to move towards more accommodative stances. It is mainly the small countries that implement, at least partially, the recommendations addressed to them. Unfortunately, there is little that the EU can do to change the status quo. Yet, the President of the Eurogroup could be held accountable for the implementation of the recommendations addressed to the euro area. The creation of National Competitiveness Boards risks making the European Semester even more complex and likely to have little impact in the countries that need them most, namely large countries and those with poor governance. To make it effective, a procedure would be needed to make national wage norms consistent at the euro-area level, which may be a very difficult objective to achieve.

The isotope composition of selenium in chondrites constrains the depletion mechanism of volatile elements in solar system materials

Solar nebula processes led to a depletion of volatile elements in different chondrite groups when compared to the bulk chemical composition of the solar system deduced from the Sun's photosphere. For moderately-volatile elements, this depletion primarily correlates with the element condensation temperature and is possibly caused by incomplete condensation from a hot solar nebula, evaporative loss from the precursor dust, and/or inherited from the interstellar medium. Element concentrations and interelement ratios of volatile elements do not provide a clear picture about responsible mechanisms. Here, the abundance and stable isotope composition of the moderately- to highly-volatile element Se are investigated in carbonaceous, ordinary, and enstatite chondrites to constrain the mechanism responsible for the depletion of volatile elements in planetary bodies of the inner solar system and to define a δ(82/78)Se value for the bulk solar system. The δ(82/78)Se of the studied chondrite falls are identical within their measurement uncertainties with a mean of −0.20±0.26‰ (2 s.d., n=14n=14, relative to NIST SRM 3149) despite Se abundance depletions of up to a factor of 2.5 with respect to the CI group. The absence of resolvable Se isotope fractionation rules out a kinetic Rayleigh-type incomplete condensation of Se from the hot solar nebula or partial kinetic evaporative loss on the precursor material and/or the parent bodies. The Se depletion, if acquired during partial condensation or evaporative loss, therefore must have occurred under near equilibrium conditions to prevent measurable isotope fractionation. Alternatively, the depletion and cooling of the nebula could have occurred simultaneously due to the continuous removal of gas and fine particles by the solar wind accompanied by the quantitative condensation of elements from the pre-depleted gas. In this scenario the condensation of elements does not require equilibrium conditions to avoid isotope fractionation. The results further suggest that the processes causing the high variability of Se concentrations and depletions in ordinary and enstatite chondrites did not involve any measurable isotope fractionation. Different degrees of element depletions and isotope fractionations of the moderately-volatile elements Zn, S, and Se in ordinary and enstatite chondrites indicate that their volatility is controlled by the thermal stabilities of their host phases and not by the condensation temperature under canonical nebular conditions.

Meteorological measurements from 8 dropsondes released during POLAR 4 flight on 1993-03-04 along a track orthogonal to the pack ice edge north west of Svalbard

Different parameterizations of subgrid-scale fluxes are utilized in a nonhydrostatic and anelastic mesoscale model to study their influence on simulated Arctic cold air outbreaks. A local closure, a profile closure and two nonlocal closure schemes are applied, including an improved scheme, which is based on other nonlocal closures. It accounts for continuous subgrid-scale fluxes at the top of the surface layer and a continuous Prandtl number with respect to stratification. In the limit of neutral stratification the improved scheme gives eddy diffusivities similar to other parameterizations, whereas for strong unstable stratifications they become much larger and thus turbulent transports are more efficient. It is shown by comparison of model results with observations that the application of simple nonlocal closure schemes results in a more realistic simulation of a convective boundary layer than that of a local or a profile closure scheme. Improvements are due to the nonlocal formulation of the eddy diffusivities and to the inclusion of heat transport, which is independent of local gradients (countergradient transport).

An emission-line survey of the Milky Way /

Includes bibliographical references

Interaction of waves and currents /

This report presents an overview of wave-current interacion, including comprehensive review of references to significant U.S. and foreign literature available through December 1981. Specific topics under review are the effects of horizontally and vertically varying currents on waves, wave refraction by currents, dissipation and turbulence, small- and medium-scale currents, caustics and focusing, and wave breaking. The results of the review are then examined for engineering applications. The most appropriate general-purpose computer program to include wave-current interaction is the Dutch Rijkswaterstaat program CREDIZ, which is based on a parabolic wave equation. Further applications include wave and current forces on structures and possibly sediment transport. The report concludes with a brief state-of-the-art review of wave-current interaction and a list of topics needing further research and development.

Depth-averaged numerical modeling for curved channels /

Cover title.

STREMR : numerical model for depth-averaged incompressible flow /

"September 1993."