Volume 530, June 2011
|Number of page(s)||6|
|Published online||27 May 2011|
1 Departamento de Astronomía, Casilla 160-C, Universidad de Concepción, Chile
2 Departamento de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Av. Gran Bretaña 1111, Playa Ancha, Casilla 5030 Valparaíso, Chile
3 Canadian Gemini Office, Herzberg Institute of Astrophysics, 5071, West Saanich Road, Victoria (BC), V9E 2E7, Canada
4 17 Bd Agutte Sembat, 38000 Grenoble, France
5 Science Systems and Applications, Inc., 10210 Greenbelt Road, Suite 600, Lanham, MD 20706, USA
6 Département de Physique and CRAQ, Université de Montréal, C.P. 6128, Succ. Centre-Ville, Montréal, Québec, H3C 3J7, Canada
e-mail: firstname.lastname@example.org; email@example.com
7 GEPI, UMR 8111 du CNRS, Observatoire de Paris-Meudon, 92195 Meudon, France
e-mail: firstname.lastname@example.org; email@example.com
8 Institut d’Astrophysique de Paris, UMR 7095 CNRS-Université Pierre & Marie Curie, 98bis, BD. Arago, 75014 Paris, France
9 Ritter Observatory, Department of Physics & Astronomy, The University of Toledo, Mail Stop #113, Toledo, Ohio 43606-3390, USA
Received: 24 January 2011
Accepted: 11 April 2011
Aims. What is the origin of the large-amplitude variability in Wolf-Rayet WN8 stars in general and WR123 in particular? A dedicated spectroscopic campaign targets the ten-hour period previously found in the high-precision photometric data obtained by the MOST satellite.
Methods. In June–August 2003 we obtained a series of high signal-to-noise, mid-resolution spectra from several sites in the λλ 4000−6940 Å domain. We also followed the star with occasional broadband (Johnson V) photometry. The acquired spectroscopy allowed a detailed study of spectral variability on timescales from ~5 min to months.
Results. We find that all observed spectral lines of a given chemical element tend to show similar variations and that there is a good correlation between the lines of different elements, without any significant time delays, save the strong absorption components of the Hei lines, which tend to vary differently from the emission parts. We find a single sustained periodicity, P ~ 9.8 h, which is likely related to the relatively stable pulsations found in MOST photometry obtained one year later. In addition, seemingly stochastic, large-amplitude variations are also seen in all spectral lines on timescales of several hours to several days.
Key words: stars: individual: HD 177230 (WR 123) / stars: Wolf-Rayet / stars: winds, outflows / stars: oscillations / stars: variables: general
Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Concil of Canada, the Institut National des Sciences de l’Univers of the Centre National de Recherche Scientifique of France, and the University of Hawaii. Based also on observations made with ESO Telescopes at the La Silla Observatory, under programme ID 271.D-5025.
Photometric data presented in Fig. 1 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/530/A151
© ESO, 2011
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