Long-term monitoring of theta1 OriC: the spectroscopic orbit and an improved rotational period

Abstract

The young O-type star theta1 OriC, the brightest star of the Trapezium cluster in Orion, is one of only two known magnetic rotators among the O stars. However, not all spectroscopic variations of this star can be explained by the magnetic rotator model. We present results from a long-term monitoring to study these unexplained variations and to improve the stellar rotational period. We want to study long-term trends of the radial velocity of theta1 OriC, to search for unusual changes, to improve the established rotational period and to check for possible period changes. We combine a large set of published spectroscopic data with new observations and analyze the spectra in a homogeneous way. We study the radial velocity from selected photo-spheric lines and determine the equivalent width of the Halpha and HeII4686 lines. We find evidence for a secular change of the radial velocity of theta1 OriC that is consistent with the published interferometric orbit. We refine the rotational period of theta1 OriC and discuss the possibility of detecting period changes in the near future.

13 pages, 6 figures, accepted for publication in A&A

References in corpus (4)

• Visual/infrared interferometry of Orion Trapezium stars: Preliminary dynamical orbit and aperture synthesis imaging of the Theta 1 Orionis C system
• The distance to the Orion Nebula Cluster
• The magnetic field and confined wind of the O star ${\theta }^1$~Orionis~C
• Optical interferometric observations of Theta 1 Orionis C from NPOI and implications for the system orbit

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• Young cluster Berkeley 59 : Properties, evolution and star formation
• The Correlation between X-Ray Line Ionization and Optical Spectral Types of the OB Stars
• MONOS.II. Orbit review and analysis for 35 single-lined spectroscopic binary systems and candidates
• The pulsating magnetosphere of the extremely slowly rotating magnetic $\beta$ Cep star ${\xi }^1$ CMa
• Detection of anomalous element distribution in the extremely slowly rotating magnetic O9.7 V star HD 54879
• The mysterious Of?p class and the magnetic O-star Theta Ori C