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

Geometry of X-ray sources in accreting black-hole binaries

7 Sept 2026, 15:15

15m

Cefalù

Talk Accretion Physics & Spectral States. Session 1.1: Accretion Foundation

Speaker

Mr Andrzej Zdziarski (N. Copernicus Astronomical Center)

Description

The structure of X-ray sources in the hard spectral state of accreting black hole binaries has been a subject of intense debate for many years. There are two main scenarios. In one, the accretion disk disappears below a certain radius and is replaced by a hot flow that emits hard X-rays. In the other, the disk continues to the innermost stable circular orbit, and the hard X-ray source is either an outflowing corona or a lamppost. Tomaso’s major involvement with this conundrum was serving as a Co-Leader (alongside the speaker) of the Team program titled “Sombreros and lampposts: The Geometry of Accretion onto Black Holes,” held at the International Space Science Institute in Bern from 2020 to 2022. I will show a short video clip of Tomaso presenting this program. Then, I will discuss recent results on the hard state of Cygnus X-1 from joint observations by XRISM, NICER, and NuSTAR, as well as from previous observations by IXPE.