The many tones of accretion - to the memory of Tomaso Belloni

Session

Timing (Belloni Session). Session 2.1: QPOs

8 Sept 2026, 09:30

Cefalù

54. QPOs in X-ray binaries

Federico Vincentelli (Coventry University)

08/09/2026, 09:30

Talk

Since the early X-ray timing studies, it has been known that both Black hole and Neutro stars X-ray binaries show narrow quasi-periodic oscillations between 0.01 and 100 Hz. Despite decades of studies, the physical origin of this intriguing phenomenon remains uncertain. In this talk I will review the main observational properties of these oscillation for both classes of systems, and describe...

78. QPOs to track the Disk Restoration signatures after Type-I X-Ray Bursts from 4U 1636−536

Suchismito Chattopadhyay (Inter-University Centre for Astronomy and Astrophysics)

08/09/2026, 10:00

Talk

Type-I thermonuclear bursts (TNBs) in neutron star low-mass X-ray binaries arise from unstable nuclear burning on the neutron star surface, whereas kHz quasi-periodic oscillations (QPOs) are believed to originate in the innermost regions of the accretion disk. The intense radiation released during a Type-I burst can perturb the inner accretion flow and thereby affect the kHz QPOs. Using 3–20...

5. Flip-Flops and QPO switching in GX 339–4 during the 2021 and 2024 NICER outbursts

Mr Federico Ferretti (Università degli Studi Roma Tre, Universitat Politecnica de Catalunya)

08/09/2026, 10:15

Talk

GX 339–4 is a low-mass X-ray binary often used as an archetype, showing typical outburst behaviour. The source undergoes a full outburst every 2–3 years, passing through all known accretion states. We used NICER data to study the spectral-timing properties of the 2024 outburst of GX 339–4 and to compare them with the 2021 outburst. In particular we focused on rapid “flip-flop” transitions,...

93. A systematic method for determining neutron star parameters from kilohertz quasi-periodic oscillations

Mrs Kateřina Klimovičová (Silesian university in Opava)

08/09/2026, 10:30

Talk

Confronting observational measurements with theoretical models of neutron star spacetimes presents several challenges. These are particularly pronounced due to the differences in the definitions of measurable physical quantities and the quantities commonly used to define the spacetime metric, with the dependence of these quantities on the NS equation of state playing a major role. Here, we...

25. Spectral–Timing Insights into Millisecond Variability in 4U 1728–34 from AstroSat

Kewal Anand (Indian Institute of Technology Kanpur, India)

08/09/2026, 10:45

Talk

We report simultaneous detection of twin kHz and $\sim 40$ Hz quasi-periodic oscillations (QPOs) in the time-resolved analysis of the AstroSat/LAXPC observation of the neutron star low mass X-ray binary, 4U 1728-34. We present the first robust detection of multiple sets of QPO triplets from a single observation whose frequencies are mutually correlated and consistent with their identification...

60. Type-B QPOs in the Hard-Intermediate State of Black Hole X-ray Binaries

Pei Jin (Kapteyn Astronomical Institute)

08/09/2026, 15:00

Talk

Black hole X-ray binaries are key laboratories for studying the behavior of matter in strong gravitational fields. During outbursts, these systems evolve through different spectral-timing states, whose distinct properties suggest changes in the geometry of the accretion flow. Previous studies have shown that the transition from the hard-intermediate state to the soft-intermediate state is...