In this talk I describe a new class of superradiant instabilities in which ultralight scalar fields extract rotational energy from neutron stars. The instability arises from the mixing of scalar and photon modes in the magnetic field of the neutron star which extract energy from the rotating magnetosphere.
Gr@v warmly congratulates the Event Horizon Telescope collaboration for the first direct image of a black hole. This discovery has had a worldwide impact, including news coverage in Portugal with the contribution of Gr@v and former Gr@v members.
In a recent paper "Spontaneous scalarisation of charged black holes: coupling dependence and dynamical features", [arXiv:1902.05079], by Gr@v members A. Pombo and E. Radu, in collaboration with a group at IST-Lisbon (P. Fernandes, C. Herdeiro and N. Sanchis-Gual), fully non-linear evolutions of the process of spontaneous scalarisation of charged black holes.
Gr@v member Valério Ribeiro was part of an international team of researchers studying thermonuclear eruptions in the Andromeda galaxy. The team published, in Nature magazine, the discovery of a super-nova remnant which is bigger than most supernova remnants. They found that the super-nova remnant was the consequence of yearly repeated eruptions over millions of years. Few of these systems are known in the galaxy due to the fact that we suffer from dust obscuration.
Gr@v member João Rosa was one of the recipients of the 2018 Alberto prize, awarded by the Portuguese Society of Relativity and Gravitation (SPRG). The prize was given for his work on the phenomenon of superradiance and its physical and astrophysical implications. The prize was shared by Richard Brito, a researcher of the Max Planck Institute for Gravitational Physics, in Berlin, Germany. The prize was delivered at the General Assembly of the SPRG, on 19th December 2018, during the XI Black Holes Workshop.
Gr@v member Pedro Cunha was one of the invited lecturers of the V Amazonia Workshop on Black Holes and Analogue Models of Gravity, that took place at the Federal University of Pará, in Belém, Brazil, from December 3rd to 7th, 2018. Cunha gave five lectures on "Geodesics and Shadows of Kerr black holes".
Gr@v member Tjarda Boekholt recently travelled to the University of Concepcion in Chile. He was invited by the Theory and Starformation Group (TSG), which is led by a team of professors including Mike Fellhauer, Dominik Schleicher, Amelia Stutz and Stefano Bovino. In the first week Tjarda lectured students on the Astrophysical Multi-purpose Software Environment (AMUSE). In particular, they discussed the coupling between N-body and hydrodynamics.
The CIDMA Young Doctor Award is a prize for a researcher within 5 years after the PhD, who has made important contributions to his or her research field. The 2018 award is granted to Gr@v member Tjarda Boekholt for his recent achievements in the field of dynamical chaos in astronomical systems. During the annual meeting of CIDMA 2018, Tjarda presented his new numerical N-body code and the ability to obtain reversible solutions to highly chaotic systems.
In a recent paper "Head on collisions of Proca Stars", [arXiv:1806.07779], by N. Sanchis-Gual et al., head-on collisions of exotic compact objects known as "Proca stars" were studied via fully non linear numerical simulations, with the goal of extracting the gravitational wave templates that such exotic objects could produce.
Our group coordinated the "Numerical Relativity and High Energy Physics" IRSES network (2012-2015). Here is a list of the global network meetings organized:
