Speaker

Eduardo Vitral, IAP

A graveyard of stars: mass-modelling of a Milky Way globular cluster

Globular clusters are old relics that orbit a host galaxy, and whose origins are still poorly constrained. Their dense profiles and self-gravitating context serve as test laboratories to a vast range of astrophysical phenomena such as intermediate-mass black holes, stellar streams, dark matter and stellar evolution. Recently, we embarked on a search for imprints of an intermediate mass black hole in the center of the nearby, core-collapsed globular cluster NGC 6397. We used data from the Hubble Space Telescope, Gaia and the MUSE spectrograph, and modeled it with the Bayesian mass-modeling code MAMPOSSt-PM. Although there was robust evidence for an inner dark mass of roughly 1000 solar masses, this mass was not point-like, but rather distributed in a region of some few percent of the luminous effective radius of the cluster. The small effective radius of the diffuse dark component suggests that it is composed of compact stars (white dwarfs and neutron stars) and stellar-mass black holes, whose inner locations are caused by dynamical friction given their high progenitor masses. I will comment on our conclusions presented in the article, on recent studies which try to constrain the fractions of each compact component that composes this dark population, as well as the enticing physics related to this stellar graveyard.