Seminars take place in the lecture room of the Spořilov building (see contacts) unless noted otherwise.
Scheduled seminars
A spectral model of accretion ejection: the JED-SAD model applied to X-ray binaries and AGN
Samuel Barnier
I will present the JED-SAD model, a spectral model stemming from self-similar magnetized accretion ejection solutions around black holes. In the JED-SAD model, the inner region is an inner Jet Emitting Disk (JED, Ferreira 1997), playing the role of the hot corona, and the outer region is a Standard Accretion Disk (SAD, Shakura & Sunyaev 1973). The JED-SAD can explain both the spectral evolution of the disk and dynamical evolution from the jet observed during X-ray binaries outbursts. I built spectral tables of the JED-SAD model and will present their application to both X-ray binaries observations and the non-linear correlation between the UV and Xray observed in AGN samples.
Measuring black hole mass and the expansion rate of the Universe with X-ray reverberation mapping
Adam Ingram
Stellar-mass black holes accreting gas from a binary partner (X-ray binaries) and supermassive black holes accreting gas from their host galaxy (active galactic nuclei, AGN) can emit a huge X-ray flux from the vicinity of the black hole event horizon. This can be exploited to probe the strong field regime of General Relativity and measure the properties of the black hole: its mass and angular momentum. For all but two objects in the Universe, the vicinity of the accreting BH is far too small to directly image, necessitating the use of mapping techniques that exploit rapid X-ray variability. I will talk about X-ray reverberation mapping, which utilises the relativistically broadened iron emission line that results from centrally emitted X-rays reflecting from the disk. Modelling the light-crossing delay between reflected and directly observed X-rays returns a black hole mass measurement. I will summarise our efforts to measure the mass of stellar and supermassive black holes with our X-ray reverberation mapping code RELTRANS, including our first proof-of-principle constraint on Cygnus X-1. I will then describe how we can use RELTRANS for an even more ambitious goal: measuring the Hubble constant, H0. This is possible because the shape of the reflection spectrum depends on the intensity of illuminating flux, meaning that modelling with RELTRANS can effectively turn bright nearby AGN into standard candles. New, independent methods to measure H0 are currently highly desirable because modelling of the cosmic microwave background returns an H0 value in >4 sigma tension with the value derived from the traditional distance ladder. I will show that the statistical precision required to prefer one of these two discrepant values is achievable with a sample of ~25 AGN. I will discuss the improvements to our model that are required to achieve such a measurement in reality.
