http://arxiv.org/abs/2002.05218
Observing the dynamics of compact astrophysical objects provides insights into their inner workings and allows to probe physics under extreme conditions. The immediate vicinity of an active supermassive black hole with its event horizon, photon ring, accretion disk, and relativistic jets is a perfect place to study general relativity, magneto-hydrodynamics, and high energy plasma physics. The recent observations of the black hole shadow of M87* with Very Long Baseline Interferometry (VLBI) by the Event Horizon Telescope (EHT) open the possibility to investigate dynamical processes there on timescales of days. In this regime, radio astronomical imaging algorithms are brought to their limits. Compared to regular radio interferometers, VLBI networks have fewer antennas. The resulting sparser sampling of the Fourier sky can only be partly compensated by co-adding observations from different days, as the source changes. Here, we present an imaging algorithm that copes with the data scarcity and the source’s temporal evolution, while simultaneously providing uncertainty quantification on all results. Our algorithm views the imaging task as a Bayesian inference problem of a time-varying flux density, exploits the correlation structure between time frames, and reconstructs a whole, $(2+1+1)$-dimensional time-variable and spectral-resolved image at once. We apply the method to the EHT observation of M87* and validate our approach on synthetic data. The obtained first time-resolved reconstruction of M87* indicates varying structures on and outside the emission ring on a time scale of days.
P. Arras, P. Frank, P. Haim, et. al.
Fri, 14 Feb 20
32/51
Comments: 24 pages, 6 figures, 4 tables
You must be logged in to post a comment.