Mass Determination of Supermassive Black Holes Governing Evolution of Radio Emitters

TL;DR

This paper develops a dynamical model for radio-emitting shells driven by disk winds around SMBHs, enabling SMBH mass estimation from radio observations of TDEs, which complements existing methods and offers rapid mass measurements.

Contribution

It introduces a universal dynamical framework for interpreting radio emission from TDEs, allowing SMBH mass inference based on shell expansion influenced by gravity, independent of ambient density profiles.

Findings

Derives power-law solutions for shell expansion in different regimes.

Identifies a universal $t^{2/3}$ scaling when gravity dominates.

Proposes radio monitoring can determine SMBH mass within months.

Abstract

Tidal disruption events (TDEs) involving supermassive black holes (SMBHs) often exhibit radio emission, yet its physical origin remains uncertain, especially in non-jetted cases. In this Letter, we formulate a general dynamical framework for a radio-emitting shell driven by disk winds and expanding through a power-law ambient medium under the influence of SMBH gravity. We derive and classify power-law-in-time solutions to the governing equations in the adiabatic regime. In particular, a universal $t^{2/3}$ scaling emerges naturally when gravitational energy dominates or is comparable to thermal energy, irrespective of the ambient density profile, whereas the classical Sedov-Taylor solution is recovered when gravity is negligible. Our analysis reveals that, in regimes where SMBH gravity governs the shell expansion, the SMBH mass can be inferred from radio observations of the shell. This approach is independent of and complementary to conventional mass estimators, with direct implications for interpreting radio-emitting TDEs and probing SMBH demographics. Our formalism further predicts that 10-100 GHz monitoring with existing and planned facilities can yield SMBH masses within months of disruption, providing a time-domain analogue to reverberation mapping.