Protostars and Planets VI, Heidelberg, July 15-20, 2013
Detections of a precessing hotspot in FU Ori?
Powell, Stacie (Institute of Astronomy, University of Cambridge)
Latham, David (Harvard Smithsonian Center for Astrophysics)
Irwin, Mike (Institute of Astronomy, University of Cambridge)
Bouvier, Jerome (l’Institut de Planétologie et d’Astrophysique de Grenoble)
Clarke, Cathie (Institute of Astronomy, University of Cambridge)
Facchini, Stefano (Institute of Astronomy, University of Cambridge)
FU Orionis systems are young stars undergoing outbursts of disc accretion and where the optical spectrum contains lines associated with both the disc photosphere and a wind component. Previous observations of the prototype FU Orionis by Herbig et al. (2003) have suggested that the photospheric lines are modulated with a period of 3.5 d corresponding to a non-axisymmetric shift from blue to red velocities in the average line profiles. We have re-observed the system at higher spectral resolution with SOPHIE and TRES, by monitoring variations of optical line profiles over 21 nights in 2007 and 35 nights in 2013 and have found periods of 3.6 and 3.2 d in the disc components respectively, consistent with the above: this implies variability mechanisms that are stable over at least 15 years, we tentatively ascribe this to an orbiting hotspot in the disc. In addition we have found that the variations in the photospheric absorption lines are confined to the blue wing of the line, centered on velocities of -9 and -60 km/s in 2007 and 2013 respectively. Consequently, we discuss the possibility of an embedded hot Jupiter precessing on an inclined orbit to explain the different velocities of the detected periodic signal between all three epochs.
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