Seminários
Os seminários do Grupo de Astrofísica são realizados quinzenalmente durante o período letivo. São abertos a toda comunidade acadêmica da UFSC, especialmente aos alunos de graduação e Pós-graduação em Física interessados nas áreas de pesquisa de astrofísica estelar, astrofísica extragaláctica ou instrumentação astronômica.
Para se inscrever e receber a agenda, mande um email para divulgaastroufsc@gmail.com com o assunto “Inscrição na lista de seminários da Astrofísica – UFSC”.
Próximo Seminário:
Nesta terça-feira (09/06), às 11h, teremos o seminário “Black Hole Accretion in the Time-Domain Era”, apresentado por Muryel Guolo.
O seminário será presencial, na sala 114 do departamento de física.
Resumo:
The study of black hole accretion has historically been largely restricted to stellar-mass black holes in X-ray binaries and long-lived active galactic nuclei (AGN) powered by massive black holes (MBHs) at the centers of galaxies. Meanwhile, the demographic studies of MBHs have been limited to those in AGN and dynamically detected quiescent MBHs in the extremely nearby universe. In the last decade, the advent of wide-field time-domain surveys has enabled a transformation in the study of tidal disruption events (TDEs), in which a star orbiting a black hole is disrupted by tidal forces, powering a bright multi-wavelength transient. This field has evolved from a largely theoretical framework with only a few observed sources into a population-level science, enabling the study of black hole accretion in real time and the investigation of previously quiescent black holes beyond the volume accessible to dynamical studies.
This thesis presents a series of studies on the multi-wavelength emission produced by such TDEs, with a strong focus on their X-ray properties. In the first part, I characterize the X-ray emission of optically selected TDEs. I implement spectral models that simultaneously fit X-ray spectra and UV/optical photometry to infer the physical parameters of these systems. Applying these models to a sample of well-observed TDEs, I recover expected—but previously unconfirmed—correlations between disk properties and inferred black hole mass, as well as independent correlations between black hole mass and host galaxy properties, extending into the intermediate-mass black hole (IMBH) regime. I also present, for the first time, the implementation of a fully time-dependent disk model within the standard X-ray fitting package XSPEC. This approach enables simultaneous fitting of multi-epoch spectral data, in which the free parameters describe only the black hole and the initial conditions, while subsequent evolution is governed solely by the dynamical equations of an evolving accretion flow. Finally, I present results on the emerging population of rare “off-nuclear” TDEs. I demonstrate the application of this modeling framework to the first optically-selected case, showing that it is powered by a “wandering” supermassive black hole. I also discuss and explain the preference for extremely massive early-type parent galaxies in the current sample.
