The mass ratio of nu SGR from ultraviolet radial velocities.

Abstract

The first positive determination of the secondary orbit of the hydrogen-deficient binary υ Sgr has been achieved by the application of cross-correlation methods to high-resolution ultraviolet (UV) spectra obtained with IUE. The mass ratio thus obtained (q = 0.63±0.01) and the consequent minimum mass for the primary (M_p sin³i/M_sun=2.52±0.05) indicate that υ Sgr is a strong candidate as a progenitor of a type Ib supernova.