Séminaire

Evolution of the Comptonizing medium of the black-hole candidate Swift J1727.8–1613 along the accretion state transition using NICER

Evidence for a strong connection between the X-ray corona and the radio jet in black hole X-ray binaries has grown significantly. During state transitions, the inferred corona size correlates with both the jet’s flux and its synchrotron spectrum properties, offering insights into jet acceleration mechanisms. We investigate the properties of the Comptonizing medium in Swift J1727.8-1613 using the time-dependent Comptonization model vkompth, with NICER observations of type-C QPOs in the hard and hard-intermediate states.

Be stars in binaries

In recent years, multiple lines of evidence have emerged supporting the idea that Be stars are mass gainers in interacting binaries. Together, these findings suggest a compelling scenario in which all Be stars are formed through binary interactions. Nevertheless, the broader implications of this scenario must be carefully examined within the context of massive binary evolution.

Prospects for Measurements of Spectral Distortions and Intensity Mapping

The experimental quest to extract the full information content of the anisotropies of the Cosmic Microwave Background (CMB) has lead to a Moore's Law-like evolution in instrument capabilities. In this seminar, I explore adapting the technologies developed for the CMB to two other, more challenging science goals: Spectral Distortions, and Intensity Mapping.   I will discuss these science topics and present concepts for instruments that could make precise measurements of these signals. I present the SPECTER instrument concept.

Speed of Gravity and Cosmology Constraints from Binary Neutron Stars using Time Delays between Gravitational Waves and Short Gamma-ray Bursts

The landmark detection of a gravitational wave (GW) from the Binary Neutron Star Merger (BNS) GW170817 and its electromagnetic counterparts allowed us to study the Universe in an entirely new way. Among the several discoveries made possible by GW170817, we can find the tightest constraints on the speed of gravity and the measurement of the Hubble constant (H0). Both of these measurements were made thanks to several assumptions and conditions that might not hold for future detections.

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