  (shortened) Spectroscopic observations of the soft X-ray transient 4U 1543-47
reveal a radial velocity curve with a period of P=1.123 +/- 0.008 days and a
semi-amplitude of K_2 = 124 +/- 4 km/sec. The mass function is f(M) = 0.22 +/-
0.02 solar masses. We derive a distance of d = 9.1 +/-1.1 kpc if the secondary
is on the main sequence. The V and I light curves exhibit two waves per orbital
cycle with amplitudes of about 0.08 mag. We modeled the light curves as
ellipsoidal variations in the secondary star and derive extreme inclination
limits of 20 <= i <= 40 deg and formal 3 sigma limits of 24 <= i <= 36 deg for
a mass ratio Q = M_1/M_2 > 1. However, there are systematic effects in the data
that the model does not account for, so the above constraints should be treated
with caution. We argue that the secondary star is still on the main sequence
and if the secondary star has a mass near the main sequence values for early
A-stars (2.3 <= M_2 <= 2.6 solar masses), then the best fits for the 3 sigma
inclination range (24 <= i <= 36 deg) and the 3 sigma mass function range (0.16
<= f(M) <= 0.28 solar masses) imply a primary mass in the range 2.7 <= M_1 <=
7.5 solar masses. Thus the mass of the compact object in 4U 1543-47 is likely
to be in excess of approximately 3 solar masses and we conclude 4U 1543-47 most
likely contains a black hole.

Astrophysics