Investigating the Black Hole in M87

Abstract

This study investigates the supermassive black hole in M87, a key target of the Event Horizon Telescope (EHT) Collaboration, that has proved a fruitful laboratory for astrophysics research. Progress in developing the capabilities of the EHT, by exploiting VLBI and enhancing data processing, imaging and analysis techniques, has delivered breakthroughs in imaging and polarisation results. While the mass of M87* is well constrained, obtaining a consensus on its spin has proved challenging, evidenced by the wide range of published results. The author sets out new methods to estimate the spin and accretion rate of the black hole, based on some key assumptions. Using EHT Collaboration imaging results of M87*, the rotational velocity of the inner edge of the accretion disk is estimated as ∼ (4.2 ± 0.3) × 107 m s−1, or ∼ 0.14 c, leading to a spin parameter of a ∼ 0.8 ± 0.1. Investigation of EHT Collaboration polarisation results, the location of the innermost stable circular orbit, plasma density and the accretion model yields further parameters. The accretion velocity is estimated at ∼ (7 ± 0.7) × 107 ms−1 and the accretion rate from the inner disk spans a range from ∼ (4 × 10−5 to 4 × 10−1) M⊙yr−1. The accretion power is estimated in the range ∼ 1034 to ∼ 1038 Js−1, which aligns with accretion-driven jet models.