WR 104: Are We Looking Down The Gun Barrel of a Future GRB?

WR 104 is the prototype for a small but growing group of stars that present the remarkably striking appearance of pinwheels. High resolution images of WR 104 show the (apparently) face-on spiral turning with an 8 month period. The pinwheel is assumed to be composed of dust produced via colliding winds in a low-inclination WR+OB binary. These assumptions have been very successful in modeling the imaging, but remain largely untested by spectroscopy.

Strong motivation for further study of this system has emerged. Recent theory suggests that some gamma-ray bursts (GRB's) are core-collapse supernovae viewed nearly pole-on. The WC class Wolf-Rayet star in WR 104 is the type of star thought to be a possible GRB progenitor. If the orbit (and thus stellar rotation axes) are pole-on, the effects on Earth's biosphere could be significant.

Confrontation of the face-on colliding-wind binary model with eight years of spectroscopy, offering full phase coverage of WR 104, is presented and many of the predictions of the model are confirmed. The spectroscopy indicates a higher inclination than that of the imaging though with the implication that there is more to these systems than currently understood.