UV, optical and near-IR diagnostics of massive stars

We present an overview of a few spectroscopic diagnostics of massive stars. We explore the following wavelength ranges: UV (1000 to 2000 A), optical (4000--7000 A) and near-infrared (mainly H and K bands). The diagnostics we highlight are available in O and Wolf-Rayet stars as well as in B supergiants. We focus on the following parameters: effective temperature, gravity, surface abundances, luminosity, mass loss rate, terminal velocity, wind clumping, rotation/macroturbulence and surface magnetic field.Comment: 12 pages, 8 figures. Proceedings of the 39th Li\`ege Astrophysical Colloquium "The multi-wavelength view of hot, massive stars". Referee's comments include

A comparison of evolutionary tracks for single Galactic massive stars

In this paper, we compare the currently available evolutionary tracks for Galactic massive stars. Our main goal is to highlight the uncertainties on the predicted evolutionary paths. We compute stellar evolution models with the codes MESA and STAREVOL. We compare our results with those of four published grids of massive stellar evolution models (Geneva, STERN, Padova and FRANEC codes). We first investigate the effects of overshooting, mass loss, metallicity, chemical composition. We subsequently focus on rotation. Finally, we compare the predictions of published evolutionary models with the observed properties of a large sample of Galactic stars. We find that all models agree well for the main sequence evolution. Large differences in luminosity and temperatures appear for the post main sequence evolution, especially in the cool part of the HR diagram. Depending on the physical ingredients, tracks of different initial masses can overlap, rendering any mass estimate doubtful. For masses between 7 and 20 Msun, we find that the main sequence width is slightly too narrow in the Geneva models including rotation. It is (much) too wide for the (STERN) FRANEC models. This conclusion is reached from the investigation of the HR diagram and from the evolution of the surface velocity as a function of surface gravity. An overshooting parameter alpha between 0.1 and 0.2 in models with rotation is preferred to reproduce the main sequence width. Determinations of surface abundances of carbon and nitrogen are partly inconsistent and cannot be used at present to discriminate between the predictions of published tracks. For stars with initial masses larger than about 60 Msun, the FRANEC models with rotation can reproduce the observations of luminous O supergiants and WNh stars, while the Geneva models remain too hot.Comment: 17 pages, 12 figures. Accepted by Astronomy & Astrophysic

John Septimus Roe and the art of navigation, c. 1815-1830

In this paper, we consider the ways in which practices of drawing and surveying shaped the geographical imagination of British mariners in the tropics. The art of navigation involved a variety of skills, notably sketching and mapping. The history of naval survey and hydrography is often written from the centre, a more‐or‐less halting narrative of science, government and empire in which prominent naval officials hold the stage. Here, we start with a different view ‐ that of the surveyor in the field, or rather on board ship, working with his eyes and his hands to make a record of the voyage. The two views are not mutually exclusive: but the perspectives they give differ in important respects. Our focus in this paper is on a single figure ‐ John Septimus Roe, who later rose to prominence as Surveyor‐General of Western Australia. We are interested here in Roe's more humble early career, as midshipman and master's mate on a number of vessels during and after the Napoleonic Wars, which took him to various sites across the British empire, formal and informal: to the European theatre of war, to North and South America, the Gulf, India, Mauritius, Burma, South‐East Asia and tropical Australia. The images of Rio de Janeiro examined here form part of a corpus which raises much wider questions about the visual culture of navigation and the experience of observation in the early nineteenth century

Necessary conditions for linear noncooperative N-player delta differential games on time scales

We present necessary conditions for linear noncooperative N-player delta dynamic games on a generic time scale. Necessary conditions for an open-loop Nash-equilibrium and for a memoryless perfect state Nash-equilibrium are proved.Comment: Partially presented at the "Fifth Symposium on Nonlinear Analysis" (SNA 2007), Torun, Poland, September 10-14, 200

Near-Infrared spectroscopy of the super star cluster in NGC1705

We study the near-infrared properties of the super star cluster NGC1750-1 in order to constrain its spatial extent, its stellar population and its age. We use adaptive optics assisted integral field spectroscopy with SINFONI on the VLT. We estimate the spatial extent of the cluster and extract its K-band spectrum from which we constrain the age of the dominant stellar population. Our observations have an angular resolution of about 0.11", providing an upper limit on the cluster radius of 2.85+/-0.50 pc depending on the assumed distance. The K-band spectrum is dominated by strong CO absorption bandheads typical of red supergiants. Its spectral type is equivalent to a K4-5I star. Using evolutionary tracks from the Geneva and Utrecht groups, we determine an age of 12+/-6 Myr. The large uncertainty is rooted in the large difference between the Geneva and Utrecht tracks in the red supergiants regime. The absence of ionized gas lines in the K-band spectrum is consistent with the absence of O and/or Wolf-Rayet stars in the cluster, as expected for the estimated age.Comment: 5 pages, 4 figures. Research Note accepted in Astronomy and Astrophysic

Parsing as Reduction

We reduce phrase-representation parsing to dependency parsing. Our reduction is grounded on a new intermediate representation, "head-ordered dependency trees", shown to be isomorphic to constituent trees. By encoding order information in the dependency labels, we show that any off-the-shelf, trainable dependency parser can be used to produce constituents. When this parser is non-projective, we can perform discontinuous parsing in a very natural manner. Despite the simplicity of our approach, experiments show that the resulting parsers are on par with strong baselines, such as the Berkeley parser for English and the best single system in the SPMRL-2014 shared task. Results are particularly striking for discontinuous parsing of German, where we surpass the current state of the art by a wide margin