How the dynamical properties of globular clusters impact their gamma-ray and X-ray emissions
Raniere Menezes
Università degli Studi di Torino, IT
It is a bit of a surprise for astronomers the fact that globular clusters (GCs) shine in gamma rays. At first glance, GCs are made mostly of old stars, which are thermal radiation emitters and should not, in principle, significantly emit gamma rays. Some insights to this question arise when we observe GCs in X-rays: their cores typically host several X-ray sources with characteristics resembling those of compact binary systems, like low-mass x-ray binaries, cataclysmic variables, and, in particular, millisecond pulsars (MSPs), which are known gamma-ray emitters. The gamma-ray emission from GCs is then attributed to their populations of MSPs. In this work, we show how stellar dynamical interactions lead to the formation of compact binary systems in GCs and how we can use the stellar number density and velocity dispersion profiles of GCs to estimate their total number of X-ray sources and gamma-ray luminosity. Furthermore, we show how secondary encounters can harden even more (or eventually ionize) these binary systems. The exceptionally high number density of stars in the cores of GCs, easily reaching more than 1000 pc-3, makes these objects real factories of compact binary systems and gives us a unique opportunity to probe the dynamics of stellar clusters.
Raniere Menezes é bacharel em Física pela Universidade Federal de Pernambuco, mestre e doutor em Astronomia pelo IAG-USP, onde trabalhou com astrofísica de altas energias usando observações de raios gama realizadas com o telescópio espacial Fermi. Foi doutorando visitante na Università degli Studi di Torino, na Itália, e no Harvard-Smithsonian Center for Astrophysics, nos EUA. Atualmente é pesquisador de pós-doutorado no Instituto Nazionale di Fisica Nucleare, seção de Turim, e astrônomo do telescópio MAGIC. Sua pesquisa trata de vários tópicos distintos em astrofísica de altas energias, como a emissão de raios gama de origem hadrônica em AGNs, a formação de sistemas binários compactos em aglomerados globulares, e a caracterização de blazares em vários comprimentos de onda.
Google Meet: https://meet.google.com/pcw-gmem-jyi
Link da transmissão: https://www.youtube.com/c/AstronomiaIAGUSP/live