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.

arXiv comment13 pages, 6 figures, accepted for publication in A&A

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• Optical interferometric observations of Theta 1 Orionis C from NPOI and implications for the system orbit

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• The three dimensional dynamic structure of the inner Orion Nebula
• A binary engine fuelling HD87643' s complex circumstellar environment, using AMBER/VLTI
• A multi-wavelength view of the Galactic center dust ridge reveals little star formation
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• Modelling clumpy PDRs in 3D - Understanding the Orion Bar stratification
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• Pumping up the [N I] nebular lines
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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
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• Detection of anomalous element distribution in the extremely slowly rotating magnetic O9.7 V star HD 54879
• The kinematic characteristics of magnetic O-type stars
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