Astrophysics News & Events

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Exploring strong gravity systems with the techniques of magnetohydrodynamics

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Speaker
Hector Olivares (from Radboud University to University of Aveiro)
Event date
Venue
Only on campus (Sala Sousa Pinto)
Event type

Gravitational wave detections, images of black hole shadows, and other impressive developments in observational astronomy allow us to study strong gravity systems in a completely new way. Being immersed in the universe, these systems are surrounded by plasma, which can be described by the equations of magnetohydrodynamics (MHD).

A waveform catalogue for Proca star collisions

The detection of gravitational waves has been one of the most exciting scientific developments of the XXIst century. These detections are theory-driven, they rely on the existence of waveform libraries, which have been constructed for binary black holes and neutron stars. Gr@v members have collaborated on the construction of the first waveform catalogue for exotic compact objects, an effort led by former Gr@v member Nicolas Sanchis Gual (now at the U. Valencia).

Dynamical descalarization with a jump during black hole merger

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Speaker
Daniela Doneva (University of Tübingen)
Event date
Venue
Online (only) - Please, note the unusual time
Event type

The black hole merger in scalar-Gauss-Bonnet gravity can lead to dynamical descalarization this is a spontaneous release of the scalar
hair of the newly formed black hole. Depending on the exact form of the Gauss-Bonnet coupling function, the stable scalarized solutions

Constraints on dark matter from observations of neutron stars and their mergers

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Speaker
Violetta Sagun (University of Coimbra)
Event date
Venue
Hybrid Sala Sousa Pinto (Math dpt) and Zoom
Event type

Compact stars due to their enormous gravitational field can accumulate a sizable amount of dark matter in their interior. Depending on its nature, an accumulated dark matter may affect the properties of neutron stars in quite different ways. I will give an overview of the impact of dark matter on various observable properties of neutron stars, i.e.

Testing General Relativity with black hole X-ray data

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Speaker
Cosimo Bambi (Fudan University)
Event date
Venue
Online (only)
Event type

The theory of General Relativity has successfully passed a large number of observational tests. The theory has been extensively tested in the weak-field regime with experiments in the Solar System and observations of binary pulsars.

The fate of the light-ring instability

In the paper "The fate of the light-ring instability" Gr@v members P. Cunha, C. Herdeiro and E. Radu, together with former member, currently at the U. Valencia, N. Sanchis-Gual, have unveiled the mystery of the fate of a large class of horizonless ultracompact objects, that could be potential black hole foils.

 

 

A long standing intriguing possibility is if the astrophysical black hole candidates could be some other kind of mysterious objects but without event horizons, the defining property of black holes.