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Paper: Observing Massive Stars with MOST: the Enigmatic WN8 Star WR123
Volume: 367, Massive Stars in Interactive Binaries
Page: 123
Authors: Lefevre, L.; Marchenko, S.V.; Moffat, A.F.J.; Acker, A.; Matthews, J.M.; Kuschnig, R.; Guenther, D.B.; Rucinski, S.M.; Sasselov, D.; Walker, G.A.H.; Weiss, W.W.
Abstract: We present preliminary results of intense photometric monitoring of the variable WN8 Wolf-Rayet star WR123 (HD177230) obtained by the recently launched MOST (Microvariability and Oscillations of STars) satellite. This first Canadian astronomical space telescope observed WR123 for 39 days non-stop during June/July 2004. A preliminary analysis of the first 30 days of data resulted in a light curve which enabled us to clearly see the chaotic behaviour of this star. Fourier analysis of this data subset shows that no periodic signal is stable for more than ~ 7 days in the low-frequency domain ( f < 1d−1), while there is a relatively stable ~ 10 h periodic component which can be seen throughout the whole 30 days in the mid frequency domain (1d−1 < f < 10d−1). This period is likely too short to be related to an orbiting compact companion (as suspected in some WN8 stars, which tend to be runaways) or too long to be due to pulsations. Rotation of a single star seems most likely, possibly related to the spin-up after the swallowing of the exploded original primary in a Thorne-Zytkow binary scenario. In addition, after detrending the data, we see no significant periodicities above the 99% confidence threshold in the high frequency domain (10d−1 < f < 1400d−1) other than harmonics related to the 101.4-minute orbital period of the satellite.
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