WR 110: a single Wolf-Rayet Star with corotating interaction regions in its wind?

• Autores: Chené, A. N.; Moffat, A. F. J.; Cameron, C.; Fahed, R.; Gamen, Roberto Claudio; Lefevre, L.; Rowe, J. F.; St louis, N.; Muntean, V.; de la Chevrotiere, A.; Guenther, D. B.; Kuschnig, R.; Matthews, J. M.; Rucinski, S. M.; Sasselov, D.; Weiss, W. W.
• Año de publicación: 2011
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: Wr 110 (Estrella); Rotation of Stars; Star Winds; Wolf-Rayet Stars; Outflows
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

A 30 day contiguous photometric run with the Microvariability and Oscillations of STars (MOST) satellite on the WN5-6b star WR 110 (HD 165688) reveals a fundamental periodicity of P = 4.08 ± 0.55 days along with a number of harmonics at periods P/n, with n ≈ 2, 3, 4, 5, and 6, and a few other possible stray periodicities and/or stochastic variability on timescales longer than about a day. Spectroscopic radial velocity studies fail to reveal any plausible companion with a period in this range. Therefore, we conjecture that the observed light-curve cusps of amplitude ~0.01 mag that recur at a 4.08 day timescale may arise in the inner parts, or at the base, of a corotating interaction region (CIR) seen in emission as it rotates around with the star at constant angular velocity. The hard X-ray component seen in WR 110 could then be a result of a high velocity component of the CIR shock interacting with the ambient wind at several stellar radii. Given that most hot, luminous stars showing CIRs have two CIR arms, it is possible that either the fundamental period is 8.2 days or, more likely in the case of WR 110, there is indeed a second weaker CIR arm for P = 4.08 days, that occurs ~two-thirds of a rotation period after the main CIR. If this interpretation is correct, WR 110 therefore joins the ranks with three other single WR stars, all WN, with confirmed CIR rotation periods (WR 1, WR 6, and WR 134), albeit with WR 110 having by far the lowest amplitude photometric modulation. This illustrates the power of being able to secure intense, continuous high-precision photometry from space-based platforms such as MOST. It also opens the door to revealing low-amplitude photometric variations in other WN stars, where previous attempts have failed. If all WN stars have CIRs at some level, this could be important for revealing sources of magnetism or pulsation in addition to rotation periods.
Fil: Chené, A. N.. Universidad de Concepción; Chile
Fil: Moffat, A. F. J.. University Of Montreal; Canadá
Fil: Cameron, C.. University Of British Columbia; Canadá
Fil: Fahed, R.. University Of Montreal; Canadá
Fil: Gamen, Roberto Claudio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico la Plata. Instituto de Astrofísica de la Plata; Argentina
Fil: Lefevre, L.. Observatoire Royal de Belgique; Bélgica
Fil: Rowe, J. F.. NASA Ames Research Center; Estados Unidos
Fil: St louis, N.. University Of Montreal; Canadá
Fil: Muntean, V.. University Of Montreal; Canadá
Fil: de la Chevrotiere, A.. University Of Montreal; Canadá
Fil: Guenther, D. B.. Saint Mary’s University. Department of Astronomy & Physics; Canadá
Fil: Kuschnig, R.. University of Toronto. Department of Astronomy & Astrophysics; Canadá
Fil: Matthews, J. M.. University of British Columbia. Department of Physics & Astronomy; Estados Unidos
Fil: Rucinski, S. M.. University of Toronto. Department of Astronomy & Astrophysics; Canadá
Fil: Sasselov, D.. Harvard-Smithsonian Center for Astrophysics; Estados Unidos
Fil: Weiss, W. W.. Technische Universitat Wien; Austria