Observing Massive Stars with the MOST Satellite: The Enigmatic WN8 Star WR123

Details Observing Massive Stars with the MOST Satellite: The Enigmatic WN8 Star WR123 Observing Massive Stars with the MOST Satellite: The Enigmatic WN8 Star WR123

Aug 2005

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005jrasc..99r.130l&link_type=abstract

Journal of the Royal Astronomical Society of Canada, Vol. 99, No. 4, p.130

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Scientific paper

We present the results of intense visual-broadband photometric monitoring of the highly variable WN8 Wolf-Rayet star WR123, obtained by the MOST (Microvariability and Oscillations of STars) satellite. This first Canadian astronomical space telescope observed WR123 every 30 seconds for 38 days non-stop during June/July 2004. The extraordinarily rich light curve enables one to clearly see the apparently chaotic behaviour of this star. Fourier analysis shows that no periodic signal is stable for more than ~7 days in the low-frequency domain (f < 1/d) and that no so-called "strange-mode" pulsations are found in the high-frequency domain (f > 10/d) down to the level of 0.2 mmag, an order of magnitude lower than theory predicts. On the other hand, there seems to be a relatively stable ~10 h periodic component throughout the whole run in the mid-frequency domain (1/d < f < 10/d). A 10 h period is probably too short to represent the rotation of the star itself as it exceeds by a factor of a few the breakup velocity of such stars (the radius and mass for WR123 are given in Crowther 1995). It is also too short to be orbital in nature as it would imply that the companion is orbiting inside the star itself. This 10 h period must be related to pulsational instabilities (although with a longer period than expected) and may thus be the key to finally revealing the motor in the high level of variability in this object, and others among the peculiar population of WN8 stars -- and possibly beyond.

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