Pulse profile modeling, the relativistic ray-tracing technique that we use to model X-ray emission from rotation-powered millisecond pulsars (mostly with NICER data) - hence measuring their mass, radius and the properties of the hot magnetic poles - involves Bayesian inference.
We rely on off-the-shelf samplers to sift through the large parameter space and deliver posterior probability distributions on all of our parameters of interest. For our simulation code X-PSI, results published to date have relied on the well-used sampler Multinest.
Different samplers have different ways of exploring the space, and various settings that can be tweaked. Tuning these to ensure accurate parameter recovery takes time and effort, and we've done a lot of work on this with Multinest for our application (see e.g. Vinciguerra et al. 2023).
But it's also good to try out completely different samplers to see if a completely different method delivers the same results! And back in 2021 @johannesbuchner.bsky.social suggested in an X-PSI github issue that we try using the sampler Ultranest as an alternative.
Comments
We agreed that it would be great to try it out, and brave statements were made that we would get to it in the second half of 2021.