出版社：SISSA, Scuola Internazionale Superiore di Studi Avanzati
摘要：The masses of compact objects like white dwarfs, neutron stars and black holes are fundamental
to astrophysics, but very difficult to measure. We present the results of an analysis of subluminous
B (sdB) stars in close binary systems with unseen compact companions to derive their masses and
clarify their nature. Radial velocity curves were obtained from time resolved spectroscopy. The
atmospheric parameters were determined in a quantitative spectral analysis. With high resolution
spectra we were able to measure the projected rotational velocity of the stars with high accuracy.
The assumption of orbital synchronization made it possible to constrain inclination angle and
companion mass of the binaries. Five invisible companions have masses that are compatible with
white dwarfs or late type main sequence stars. But four sdBs have very massive companions like
heavy white dwarfs, neutron stars or even black holes. Such a high fraction of massive compact
companions can not be explained with current models of binary evolution.
