Browsing by Author "Foellmi, C."

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    On the abundances of GRO J1655-40
    (2007) Foellmi, C.; Dall, T. H.; Depagne, E.
    Context. The detection of overabundances of alpha-elements and lithium in the secondary star of a black- hole binary provides important insights about the formation of a stellar-mass black- hole alpha-enhancement might theoretically also be the result of pollution by the nucleosynthesis occurring during an outburst, or through spallation by the jet. Aims. We study the abundances, and their possible variations with time, in the secondary star of the runaway black- hole binary GRO J1655 - 40, in order to understand their origin.
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    On the distance of GRO J1655-40
    (2006) Foellmi, C.; Depagne, E.; Dall, T. H.; Mirabel, I. F.
    Aims. We challenge the accepted distance of 3.2 kpc of GRO J1655-40. We present VLT-UVES spectroscopic observations to estimate the absorption toward the source, and determine a maximum distance of GRO J1655-40.
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    Spectroscopy of SMC Wolf-Rayet stars suggests that wind clumping does not depend on ambient metallicity
    (2007) Marchenko, S. V.; Foellmi, C.; Moffat, A. F. J.; Martins, F.; Bouret, J. -C.; Depagne, E.
    The mass-loss rates of hot, massive, luminous stars are considered a decisive parameter in shaping the evolutionary tracks of such stars and influencing the interstellar medium on galactic scales. The small-scale structures ( clumps) that are omnipresent in such winds may reduce empirical estimates of mass-loss rates by an evolutionarily significant factor of >= 3. So far, there has been no direct observational evidence that wind clumping may persist at the same level in environments with a low ambient metallicity, where the wind-driving opacity is reduced. Here we report the results of time-resolved spectroscopy of three presumably single Population I Wolf-Rayet stars in the Small Magellanic Cloud, where the ambient metallicity is similar to 1/5 Z(circle dot). We detect numerous small-scale emission peaks moving outward in the accelerating parts of the stellar winds. The general properties of the moving features, such as their velocity dispersions, emissivities, and average accelerations, closely match the corresponding characteristics of small-scale inhomogeneities in the winds of Galactic Wolf-Rayet stars.
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    VSOP
    (2007) Dall, T. H.; Foellmi, C.; Pritchard, J.; Lo Curto, G.; Prieto, C. Allende; Bruntt, H.; Amado, P. J.; Arentoft, T.; Baes, M.; Depagne, E.; Fernandez, M.; Ivanov, V.; Koesterke, L.; Monaco, L.; O'Brien, K.; Sarro, L. M.; Saviane, I.; Scharwaechter, J.; Schmidtobreick, L.; Schuetz, O.; Seifahrt, A.; Selman, F.; Stefanon, M.; Sterzik, M.
    Context. About 500 new variable stars enter the General Catalogue of Variable Stars (GCVS) every year. Most of them however lack spectroscopic observations, which remains critical for a correct assignement of the variability type and for the understanding of the object.