# M87 black hole mass and spin estimate through the position of the jet boundary shape break

## TL;DR

This paper introduces a novel method to estimate the mass and spin of the supermassive black hole in M87 by analyzing the transition in the jet boundary shape, supported by observational data and MHD modeling.

## Contribution

The paper presents a new approach linking jet boundary shape transitions to black hole properties, combining observational data with magnetohydrodynamic modeling.

## Key findings

- Black hole mass estimate is larger than previous estimates.
- Jet boundary transition correlates with flow regime change.
- Magnetic fields play a crucial role in jet dynamics.

## Abstract

We propose a new method of estimating a mass of a super massive black hole residing in the center of an active galaxy. The active galaxy M87 offers a convenient test case for the method due to the existence of a large amount of observational data on the jet and ambient environment properties in the central area of the object. We suggest that the observed transition of a jet boundary shape from a parabolic to a conical form is associated with the flow transiting from the magnetically dominated regime to the energy equipartition between plasma bulk motion and magnetic field. By coupling the unique set of observations available for the jet kinematics, environment and boundary profile with our MHD modelling under assumption on the presence of a dynamically important magnetic field in the M87 jet, we estimate the central black hole mass and spin. The method leads us to believe that the M87 super massive black hole has a mass somewhat larger than typically accepted so far.