Mass flow in the 07f binary UW Canis Majoris

The ultraviolet spectrum of the eclipsing binary UW CMa (07f+O--B) has been observed by the Princeton telescope spectrometer on the Copernicus satellite in the wavelength region from about 950--1560 A at a resolution corresponding to 0.2 A. A number of stellar and interstellar lines appear in the spectrum. The following lines showing P Cygni characteristics have been observed: C iii (977, 1175 A), S iv (1062, 1072 A), P v (1117 A), Fe iii +Si iv (1122 A), P v+S iv (1128 A), N v (1238, 1242 A), Si iv (1393, 1402 A), and C iv (1549 A). The centers of the absorption components of the P Cygni lines yield radial velocities of from -200 to -800 km s-1, while the peaks of the emission components are shifted by +400 to +800 km s-1. These velocities are significantly larger than the projected orbital velocity of about 200 km s-1, and indicate that gas motions in the system are occurring. A mass-loss rate of about 3times10-6 solar masses per year is estimated. A few photospheric absorption lines from the O7f component are also present: N iii (1006), 1183, 1184 A) and possibly He ii (1084 A)