Studying the photometric and spectroscopic variability of the magnetic hot supergiant ζ Orionis Aa
- Author(s)
- B. Buysschaert, Coralie Neiner, Noel D. Richardson, Rainer Kuschnig, Werner Wolfgang Weiss, Tahina Ramiaramanantsoa, Alexandre David-Uraz, Herbert Pablo, M. E. Oksala, Anthony F J Moffat, Ronald E. Mennickent, S. Legeza, C. Aerts, G. N. Whittaker, A. Popowicz, Gerald Handler, Gregg A. Wade
- Abstract
Massive stars play a significant role in the chemical and dynamical evolution of galaxies. However, much of their variability, particularly during their evolved supergiant stage, is poorly understood. To understand the variability of evolved massive stars in more detail, we present a study of the O9.2Ib supergiant ζ Ori Aa, the only currently confirmed supergiant to host a magnetic field. We have obtained two-color space-based BRIght Target Explorer photometry (BRITE) for ζ Ori Aa during two observing campaigns, as well as simultaneous ground-based, high-resolution optical CHIRON spectroscopy. We perform a detailed frequency analysis to detect and characterize the star's periodic variability. We detect two significant, independent frequencies, their higher harmonics, and combination frequencies: the stellar rotation period P
rot = 6.82 ± 0.18 d, most likely related to the presence of the stable magnetic poles, and a variation with a period of 10.0 ± 0.3 d attributed to circumstellar environment, also detected in the Hα and several He I lines, yet absent in the purely photospheric lines. We confirm the variability with P
rot/4, likely caused by surface inhomogeneities, being the possible photospheric drivers of the discrete absorption components. No stellar pulsations were detected in the data. The level of circumstellar activity clearlydiffers between the two BRITE observing campaigns. We demonstrate that ζ Ori Aa is a highly variable star with both periodic and non-periodic variations, as well as episodic events. The rotation period we determined agrees well with the spectropolarimetric value from the literature. The changing activity level observed with BRITE could explain why the rotational modulation of the magnetic measurements was not clearly detected at all epochs.
- Organisation(s)
- Department of Astrophysics
- External organisation(s)
- Université de recherche Paris Sciences et Lettres, Katholieke Universiteit Leuven, University of Toledo, Technische Universität Graz, California Lutheran University, University of Montreal, Florida Institute of Technology, Universidad de Concepción, Radboud University, University of Toronto, Silesian University of Technology, Polish Academy of Sciences (PAS), Royal Military College of Canada
- Journal
- Astronomy & Astrophysics
- Volume
- 602
- No. of pages
- 20
- ISSN
- 0004-6361
- DOI
- https://doi.org/10.1051/0004-6361/201630318
- Publication date
- 06-2017
- Peer reviewed
- Yes
- Austrian Fields of Science 2012
- 103003 Astronomy, 103004 Astrophysics
- Keywords
- ASJC Scopus subject areas
- Astronomy and Astrophysics, Space and Planetary Science
- Portal url
- https://ucrisportal.univie.ac.at/en/publications/c52abd87-e4de-4675-bfbd-cd292756939a