Probing Strong Gravitational Fields in X-ray Novae

Most X-ray novae (aka soft X-ray transients) contain black hole primaries. In particular, the large mass functions measured for six X-ray novae directly clinch the argument (within general relativity) that they contain black holes. These firm dynamical results are discussed, and the urgent need to determine precise masses for black holes is stressed. The dynamical evidence for black holes is convincing but it is indirect. Now it appears that direct evidence may be at hand. Three recent studies have revealed phenomena that very likely probe strong gravitational fields: (1) a comparison of the luminosities of black hole systems and neutron star systems has yielded compelling evidence for the existence of event horizons; (2) RXTE observations of fast, stable QPOs have probed the very inner accretion disks of two black holes; and (3) three different types of low energy spectra have been linked to different black-hole spin states (e.g. Kerr vs. Schwarzschild).Comment: To appear in "Accretion Processes in Astrophysical Systems," Proceedings of the 8th Annual Astrophysics Conference in Maryland, eds. S.S. Holt & T. Kallman (NY: AIP

Relations Without Polyadic Properties: Albert the Great On the Nature and Ontological Status of Relations

I think it would be fair to say that, until about 1900, philosophers were generally reluctant to admit the existence of what are nowadays called polyadic properties.1 It is important to recognize, however, that this reluctance on the part of pre-twentieth-century philosophers did not prevent them from theorizing about relations. On the contrary, philosophers from the ancient through the modern period have had much to say about both the nature and the ontological status of relations. In this paper I examine the views of one such philosopher, namely, Albert the Grea