Oscillations in the Massive Wolf-Rayet Star WR 123 with the M O S T Satellite

Abstract

We present the results of intensive visual-broadband photometric monitoring of the highly variable WN8 Wolf-Rayet star WR 123, obtained by the MOST (Microvariability and Oscillations of STars) satellite. This first Canadian astronomical space telescope observed WR 123 for 38 days nonstop during 2004 June and July. Fourier analysis shows that no periodic signal is stable for more than several days in the low-frequency domain (f < 1 day-1), where most of the stochastic power is contained. Also, no significant variability is seen in the high-frequency domain (10 day-1 < f < 1400 day-1) down to the level of 0.2 mmag, an order of magnitude lower than theoretical predictions for strange-mode pulsations. On the other hand, there seems to be a relatively stable 9.8 hr periodic signal present throughout the whole run. This period is probably too short to represent the axial rotation of the star, unless it is related to multiple substructures equidistantly spread along the stellar equator. It is also too short to be orbital in nature; it is more likely to be related to pulsational instablilities (although with a much longer period than expected), thus finally revealing a possible fundamental driver behind the highly variable wind of this object, and others of similar type.