Black Hole Spacetime and Properties of Accretion Flows and Jets Probed by Black Hole Explorer: Science Cases Proposed by BHEX Japan Team

TL;DR

The paper discusses the science potential of the Black Hole Explorer (BHEX) space VLBI mission to image black hole shadows, jets, and magnetic fields, advancing understanding of black hole physics and accretion processes.

Contribution

It proposes specific science cases for BHEX, including imaging black hole shadows, plasma injection regions, and magnetic field structures, which are novel applications of space VLBI.

Findings

Imaging of M87's shadow can constrain black hole spin.

Detection of plasma injection regions can elucidate jet formation.

Polarization measurements can reveal magnetic field and electron properties.

Abstract

Black Hole Explorer (BHEX) is a space VLBI mission concept, which can probe the black hole spacetime and the plasma properties including the magnetic fields of the accretion flows and relativistic jets. We propose science cases anticipated to be addressed by BHEX mainly via the imaging of the target objects, whose observational features appear in several microarcsecond scale. An appearance of a crescent-shaped shadow in a bright state of the M87 will be able to constrain the magnitude of the black hole spin. A possible appearance of the plasma injection region in the vicinity of the black hole results in the formation of the multiple ring structure and may enable us to understand the jet formation processes. In addition, The separation of linear and circular polarization fluxes and reversal of circular polarization will constrain the magnetic field structure and the thermal properties of the electrons, respectively. Other topics including the test of the gravitational theory are also being discussed.