Welcome and introduction

• Elizabeth Sarah Long

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Testing the horizon of black holes with gravitational waves

• Elisa Maggio (University of Rome La Sapienza)

Room: Zoom only Black holes are the most compact objects in the Universe. According to General Relativity, black holes are endowed with an event horizon that hides a singularity where Einstein’s theory breaks down. Recently, gravitational waves opened the possibility to probe the existence of horizons and investigate the nature of compact objects. This is of particular interest in view of some quantum-gravity models which predict the existence of horizonless exotic compact objects. Such exotic compact objects can emit a modified gravitational wave signal with respect to the black hole case and late-time gravitational wave echoes as characteristic fingerprints. In this talk, I overview the phenomenology of exotic compact objects and their detectability with current and future experiments.

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The Imaging X-ray Polarimetry Explorer (IXPE): a new window for Astrophysics

• Riccardo Ferrazzoli (INAF)

Room: Zoom only The field of X-ray polarimetry, that has been dormant for decades, will enter a new golden age with the launch of the NASA-ASI Imaging X-ray Polarimetry Explorer (IXPE) in November 2021. IXPE will perform for the first time spatially resolved X-ray polarimetry of a wide range of X-ray sources, providing insights on their magnetic field geometry and emission processes. In this talk I will give an overview of the mission and its scientific goals, with an emphasis on the extended sources that IXPE will observe, such as supernova remnants, extragalactic jets, and the molecular clouds in the Galactic center.

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