Séminaire IPAG

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Flip-floping states in X-ray binaries

jeudi 13 février 2025 - 11h00

Grégoire Marcel - 
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X-ray binaries are binary systems composed of a star and a compact object, black hole or neutron star. These systems are amazing laboratories to understand accretion-ejection phenomena. These systems spend most of their lives in a barely detectable state, sometimes for years, before experiencing sudden outbursts in luminosities that last up to a few months. During a typical outburst the entire spectrum changes, but what is the most striking is what happens in X-rays. In this talk, I will present an analysis of the 2021 outburst from the black hole X-ray binary GX339–4, focusing on rapid flux transitions observed around MJD 59300, called flip-flop. These flip-flops are characterized by sudden switches between two distinct luminosity states: a bright state featuring a quasi-periodic signal (usually called a QPO) and a dim state dominated by strong broad-band noise (BBN). Using high-cadence NICER data, we show that these transitions occur on remarkably short timescales, with nearly 50 state changes recorded within a single observation. Despite the stark differences in timing properties, the spectral energy distributions (SEDs) of both states remain strikingly similar, with only minor variations in the soft X-ray band. While the exact origin of the flip-flops and QPOs remains elusive, this study highlights the importance of combining timing and spectral analyses to understand the complex dynamics of accretion flows in black hole X-ray binaries. I will conclude by discussing the broader implications of these findings for accretion physics.

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Hôtes : Pierre-Olivier Petrucci

Salle Manuel Forestini, 414 rue de la piscine, 38400 Saint Martin d'Hères