Wolf-Rayet Stars

wolf-rayet stars as progenitors of gamma-ray bursts

We are currently carrying out a spectropolarimetry survey of Galactic Wolf-Rayet stars in an effort to study the progenitors of gamma-ray bursts (GRBs). This survey utilizes Gary Schmidt's SPOL instrument on the Steward Observatory 90-inch and MMT telescopes.

The most widely accepted model of gamma-ray bursts is the collapsar model in which a massive star undergoes core collapse resulting in a black hole and an accretion disk. In this model there is a preferred axis which is generally attributed to rapid rotation of the progenitor but could also be the result of magnetic fields or tidal effects of a companion. The gamma-ray burst is the result of a relativistic jet which propagates along the preferred axis through the still collapsing star. The collapsar model requires that progenitor has already shed its hydrogen envelope, otherwise the jet would lose its energy and no burst would occur. Wolf-Rayet stars are massive stars which have shed their hydrogen envelopes and therefore are an excellent candidate for the progenitors of GRBs.

We are using spectropolarimetry to probe the geometric structure of the mass loss envelope of Wolf-Rayet stars. Polarization will result from asymmetries in this structure which can be attributed to the same physics which produce the preferred axis of a gamma-ray burst. To date we have observed xx Galactic Wolf-Rayet stars using spectropolarimetry. The results will be combined with the existing measurements of just 29 stars to correlate asymmetries with stellar parameters and environment to identify the likely progenitors of gamma-ray bursts. Upon completion we will have increased the measurement of spectropolarimetry of Wolf-Rayet stars by more than 60%.

Presentations

The VIIth catalogue of galactic Wolf-Rayet stars
MMT Catalog of Wolf-Rayet stars
Finder Charts
Airmass Plots
Observing Logs
Observing Proposals
Spectral Classification
Wolf-Rayet Bibliography
Wolf-Rayet Data from SIMBAD (BIG!!)
Local Group Survey, Stellar Content

Updated: Thursday, 31-Jul-2008 18:06:45 MST