Detecting Flaring Structures in Sagittarius A* with (Sub)Millimeter VLBI

TL;DR

This paper demonstrates that (sub)millimeter VLBI can detect periodic flaring activity in Sagittarius A* caused by orbiting hot-spots or disk instabilities, aiding in probing the black hole environment.

Contribution

It introduces methods to detect periodicity in Sgr A* flares using closure quantities across various models, enhancing black hole environment studies.

Findings

Periodic signals are detectable with VLBI closure quantities.

Methods are applicable to diverse models including jets and disk instabilities.

VLBI can probe structures near the event horizon of Sgr A*.

Abstract

Multiwavelength monitoring observations of Sagittarius A* exhibit variability on timescales of minutes to hours, indicating emission regions localized near the event horizon. (Sub)Millimeter-wavelength VLBI is uniquely suited to probe the environment of the assumed black hole on these scales. We consider a range of orbiting hot-spot and accretion-disk models and find that periodicity in Sgr A* flares is detectable using closure quantities. Our methods are applicable to any model producing source structure changes near the black hole, including jets and magnetohydrodynamic disk instabilities, and suggest that (sub)millimeter VLBI will play a prominent role in investigating Sgr A* near the event horizon.