Volume 574, February 2015
|Number of page(s)||38|
|Published online||09 February 2015|
Radial dependence of line profile variability in seven O9–B0.5 stars⋆
LUPM, Université Montpellier 2, CNRS, Place Eugène Bataillon, 34095
2 Observatório do Valongo, Universidade do Rio de Janeiro, Ladeira Pedro António, 43, CEP 20080-090, Brasil
3 Department of Physics and Astronomy & Pittsburgh Particle physics, Astrophysics and Cosmology Center (PITT PACC), University of Pittsburgh, 3941 O’Hara Street, Pittsburgh, PA 15260, USA
4 IRAP, CNRS & Univ. de Toulouse, 14 Av. E. Belin, 31400 Toulouse, France
5 LAM–UMR 6110, CNRS & Université de Provence, rue Frédéric Joliot-Curie, 13388, Marseille Cedex 13, France
Received: 25 March 2014
Accepted: 15 September 2014
Context. Massive stars show a variety of spectral variabilities: discrete absorption components in UV P-Cygni profiles, optical line profile variability, X-ray variability, and radial velocity modulations.
Aims. Our goal is to study the spectral variability of single OB stars to better understand the relation between photospheric and wind variability. For that, we rely on high spectral resolution and on high signal-to-noise ratio optical spectra collected with the spectrograph NARVAL on the Télescope Bernard Lyot at Pic du Midi.
Methods. We investigated the variability of twelve spectral lines by means of the temporal variance spectrum. The selected lines probe the radial structure of the atmosphere from the photosphere to the outer wind. We also performed a spectroscopic analysis with atmosphere models to derive the stellar and wind properties and to constrain the formation region of the selected lines.
Results. We show that variability is observed in the wind lines of all bright giants and supergiants on a daily timescale. Lines formed in the photosphere are sometimes variable, sometimes not. The dwarf stars do not show any sign of variability. If variability is observed on a daily timescale, it can also (but not always) be observed on hourly timescales, albeit with lower amplitude. There is a very clear correlation between amplitude of the variability and fraction of the line formed in the wind. Strong anti-correlations between the different parts of the temporal variance spectrum are observed.
Conclusions. Our results indicate that variability is stronger in lines formed in the wind. A link between photospheric and wind variability is not obvious from our study, since wind variability is observed regardless of the level of photospheric variability. Different photospheric lines also show different degrees of variability.
Key words: stars: massive / stars: atmospheres / stars: winds, outflows / stars: variables: general
Appendices are available in electronic form at http://www.aanda.org
© ESO, 2015
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