Jul 15 – 19, 2024
Perimeter Institute for Theoretical Physics
America/Toronto timezone

Photon Rings and Shadow Size for General Axi-Symmetric and Stationary Integrable spacetimes

Jul 15, 2024, 3:45 PM
15m
Federation Hall (University of Waterloo)

Federation Hall

University of Waterloo

Contributed Talk Contributed Talks

Speaker

Kiana Salehi (Perimeter Institute/University of Waterloo)

Description

There are now multiple direct probes of the region near black hole horizons, including direct imaging with the Event Horizon Telescope (EHT). As a result, it is now of considerable interest to identify what aspects of the underlying spacetime are constrained by these observations. For this purpose, we present a new formulation of an existing broad class of integrable, axisymmetric, stationary spinning black hole spacetimes, specified by four free radial functions, that makes manifest which functions are responsible for setting the location and morphology of the event horizon and ergosphere. We explore the size of the black hole shadow and high-order photon rings for polar observers, approximately appropriate for the EHT observations of M87*, finding analogous expressions to those for general spherical spacetimes. Of particular interest, we find that these are independent of the properties of the ergosphere, but does directly probe on the free function that defines the event horizon. Based on these, we extend the nonperturbative, nonparametric characterization of the gravitational implications of various near-horizon measurements to spinning spacetimes. Finally, we demonstrate this characterization for a handful of explicit alternative spacetimes.

Keywords Rotating black holes, General relativity, Non-standard theories of gravity
arXiv reference, if applicable: arXiv:2311.01495
Contact Email [email protected]

Primary authors

Dr Avery Broderick (Perimeter Institute and University of Waterloo) Kiana Salehi (Perimeter Institute/University of Waterloo)

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External references