SUMMARY OF PROPOSAL 62012

DR. MICHAEL FRANCIS CORCORAN CORCORAN@BARNEGAT.GSFC.NASA.GOV

NASA-GSFC/USRA
CODE 660.2
GREENBELT
MD USA 20771
Tel: 301-286-5576 Fax: 301-286-1629
Medium: CD ROM
Subject: STARS

ABSTRACT

We have obtained {\it ASCA} X-ray spectra of the canonical colliding-wind binary star WR 140 (WC7+OB) during the PV, AO1 and AO5 intervals. We need continuing {\it ASCA} monitoring to measure the variability of the X-ray spectrum through the entire orbit. This X-ray lightcurve will provide the most accurate measure of the interaction region and redefine the physics of colliding-wind systems. The previous {\it ASCA} observations show that the spectrum has changed from a highly-absorbed, predominantly thermal spectrum to a less absorbed but {\it predominantly non-thermal} model. This is a very surprising result, not predicted in standard colliding wind models, and suggests that Fermi acceleration of particles at the wind shock boundary is important.