Interferometry, spectroscopy and astrometry of the bright eclipsing system Delta Velorum

The bright southern star Delta Vel is a multiple system comprising at least three stars. Its brightest component, Delta Vel A, was identified in 2000 as one of the brightest eclipsing system in the sky. Its eclipses are easily observable with the unaided eye, a remarkable property shared only by Algol, Beta Aur, Alpha CrB and Psi Cen. We determined dynamical masses from a combination of spectroscopy, high-precision astrometry of the orbits of Aab-B and Aa-Ab using adaptive optics (VLT/NACO) and optical interferometry (VLTI/AMBER). The main eclipsing component is a pair of A-type stars in rapid rotation. We modeled the photometric and radial velocity measurements of the eclipsing pair Aa-Ab using a self consistent method based on physical parameters (mass, radius, luminosity, rotational velocity). From this modeling, we derive the fundamental parameters of the eclipsing stars with a typical accuracy of 1%. We find that they have similar masses, respectively 2.43 +/- 0.02 and 2.27 +/- 0.02 Msun. The physical parameters of the tertiary component (Delta Vel B) are also derived, although to a lower accuracy, as well as the parallax of the system, 39.8 +/- 0.4 mas. This value is in satisfactory agreement (-1.2 sigma) with the Hipparcos parallax of the system (pi_Hip =40.5 +/- 0.4 mas).Comment: 4 pages, 5 figures, in GREAT-ESF Workshop 'Orbital Couples: "Pas de Deux" in the Solar System and the Milky Way', Paris, IMCCE proceedings, in pres

Mean angular diameters, distances and pulsation modes of the classical Cepheids FF Aql and T Vul - CHARA/FLUOR near-infrared interferometric observations

We report the first angular diameter measurements of two classical Cepheids, FF Aql and T Vul, that we have obtained with the FLUOR instrument installed at the CHARA interferometric array. We obtain average limb-darkened angular diameters of \theta_LD = 0.878 +/- 0.013 mas and \theta_LD = 0.629 +/- 0.013 mas, respectively for FF Aql and T Vul. Combining these angular diameters with the HST-FGS trigonometric parallaxes leads to linear radii R = 33.6 +/- 2.2 Rsol and R = 35.6 +/- 4.4 Rsol, respectively. The comparison with empirical and theoretical Period-Radius relations leads to the conclusion that these Cepheids are pulsating in their fundamental mode. The knowledge of the pulsation mode is of prime importance to calibrate the Period-Luminosity relation with a uniform sample of fundamental mode Cepheids

How Jean-Claude Juncker and Pierre Moscovici laid the groundwork for the EU’s post-COVID fiscal policy

The EU’s fiscal rules, which state that governments should run budget deficits no higher than 3% of GDP and maintain a public debt no higher than 60% of GDP, have been suspended during the Covid-19 pandemic and there are now growing calls for them to be reformed or abandoned altogether. Drawing on a new study, Frédéric Mérand documents how Jean-Claude Juncker, Pierre Moscovici and other figures within the European Commission laid the groundwork for this paradigm shift in EU fiscal governance

Flexible Spectro Interferometric modelling of OIFITS data with PMOIRED

Despite image reconstruction becoming more widespread when interpreting OIFITS Data, model fitting in u,v space often remains the best way to interpret data, either because of the sparsity of the data, or because a quantitative measurement needs to be done. PMOIRED, is a flexible Python library to visualize, manipulate and model OIFITS data using simple geometric models. The strength of PMOIRED resides in its capability to combine linearly various simple components to create complex scenes, while linking, constraining, and adding priors to fitted parameters. The code also enables grid search to find global minima, as well as data resampling to better evaluate uncertainties. In addition to analytical functions, arbitrary radial profiles, azimuthal variations or sparse wavelet modelling of spectra are implemented.Comment: 8 pages, 3 figures. Proceeding of SPIE Telescopes+Instrumentation 2022. Code referenced at http://ascl.net/code/v/328

L’Europe dans la culture stratégique canadienne, 1949-2009

S’ appuyant sur la notion de culture stratégique, cet article démontre l’existence d’ une tension historique entre européanisme, continentalisme et internationalisme dans la politique étrangère canadienne. Cette tension fondatrice est explorée sur le plan conceptuel, mais également dans les prises de position concrètes des gouvernements et des partis politiques depuis la fin de la Deuxième Guerre mondiale. En s’ alignant plus ouvertement sur Washington, le gouvernement conservateur de Stephen Harper (2006-2009) est le premier à privilégier le continentalisme de manière aussi unidimensionnelle. Même si le déclin de l’ européanisme ne fait aucun doute, la résilience anticipée de la culture stratégique nous amène à relativiser cette tentative de transformation de la politique étrangère canadienne.Building on the notion of strategic culture, this article substantiates the existence of a historical tension between Europeanism, continentalism and internationalism in Canadian foreign policy. We explore this basic tension at the conceptual level, but also through the positions taken by governments and political parties since World War ii. We note that, by aligning itself on Washington, the Conservative government of Stephen Harper (2006-2009) is the first to privilege continentalism exclusively and at the expense of other perspectives. While the decline of Europeanism seems inevitable, the anticipated resilience of Canada’ s strategic culture leads us to question this attempt at transforming Canadian foreign policy

France’s Return to NATO: The Death Knell for ESDP?

Our article focuses on the likely impact of France's return to NATO's integrated military command on the future of the European security and defense policy (ESDP). First, we describe the triangular relationship between France's defense, NATO and European defense policies that dominated the era of the Gaullist–Mitterrandist consensus (1958–95) and its gradual erosion under Jacques Chirac's tenure (1995–2007). Second, we explain the context in which President Sarkozy made the decision in 2007 to rejoin the Allied military command. Relying on interviews with French foreign and defense policy-makers, we address the extent to which ESDP considerations really played a role. Finally, we develop four scenarios for the future of European defense: (1) ESDP gets a new lease of life; (2) France becomes a normal player in a NATO-dominated Europe; (3) NATO and ESDP work out of a division of labor; and (4) France becomes the Trojan horse of European cooperation inside NATO. To develop each scenario, we rely on rationalist and constructivist mechanisms drawn from International Relations theory