Scott Tremaine (IAS) and Feryal Ozel (Arizona) gave back-to-back group-meeting talks, with Tremaine on the triple-star systems in our Galaxy, comparing with the binary systems, and giving a possible explanation for the observation that very close binaries are incredibly likely to have third companions at large radius. Ozel showed that GR effects make the measurements of neutron star masses and radii non-trivial. But she also showed that some of the softer equations of state can be ruled out with current data. Her analyses rely on models of the x-ray bursts, but she argued that these models are mature. The data are amazing! In the afternoon, Tremaine discussed the long-term stability and dynamics of our Solar System and others. He argued that the system is chaotic with a Liapunov time of order 100 Myr, but stable on timescales much, much longer than this.
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