Bounds on ultralight bosons from the Event Horizon Telescope observation of Sgr A$^*$

TL;DR

This paper uses Event Horizon Telescope observations of Sgr A* to set new bounds on the mass of ultralight bosons, leveraging black hole superradiance effects and considering self-interacting axions, with implications for beyond Standard Model physics.

Contribution

It introduces novel constraints on ultralight boson masses from Sgr A* observations, including effects of self-interactions, expanding the parameter space explored.

Findings

Bounds on ultralight boson mass derived from Sgr A* spin data

Constraints on decay constants for self-interacting axions

Future BH observations can tighten these bounds

Abstract

Recent observation of Sagittarius A$^*$ (Sgr A$^*$) by the Event Horizon Telescope (EHT) collaboration has uncovered various unanswered questions in black hole (BH) physics. Besides, it may also probe various beyond the Standard Model (BSM) scenarios. One of the most profound possibilities is the search for ultralight bosons (ULBs) using BH superradiance (SR). EHT observations imply that Sgr A$^*$ has a non-zero spin. Using this observation, we derive bounds on the mass of ULBs with purely gravitational interactions. Considering self-interacting ultralight axions, we constrain new regions in the parameter space of decay constant, for a certain spin of Sgr A$^*$. Future observations of various spinning BHs can improve the present constraints on ULBs.