white-dwarf binaries, importance sampling

In the astro seminar, Carlos Badenes (Pitt) talked about white-dwarf–white-dwarf binaries and an inferred rate of inspiral, based on SDSS spectra split up exposure by exposure: The orbits of the soon-to-merge white dwarfs are so fast and short-period that even the twenty-minute intervals between spectral exposures in SDSS are long enough to show velocity changes! He finds a merger event rate for the binaries large enough to explain the type-Ia supernova rate, but only if he permits sub-Chandrasekhar total masses to make the SNe. That is, he gets enough events, but they tend to be low-mass.

Tim Morton (Princeton) spent the day at NYU to talk exoplanets, sampling, selection functions, marginalized likelihoods, and so on. We had a productive talk about making high-performance importance-sampling code to compute the marginalized likelihoods.