Multi-Wavelength Study of Sgr A*: The Short Time Scale Variability

TL;DR

This study investigates the short time scale variability of SgrA* across multiple wavelengths, revealing insights into emission mechanisms and constraining the size and nature of the emitting region.

Contribution

It provides the first detailed analysis of minute-scale variability in SgrA* across IR, X-ray, and radio wavelengths, linking observations to emission models and outflow evidence.

Findings

Most power spectral density occurs on hourly time scales.

Minute-scale variability constrains the size of the emission region.

Relativistic outflows are suggested by rapid fluctuations.

Abstract

To understand the correlation and the radiation mechanism of flare emission in different wavelength bands, we have coordinated a number of telescopes to observe SgrA* simultaneously. We focus only on one aspect of the preliminary results of our multi-wavelength observing campaigns, namely, the short time scale variability of emission from SgrA* in near-IR, X-ray and radio wavelengths. The structure function analysis indicate most of the power spectral density is detected on hourly time scales in all wavelength bands. We also report minute time scale variability at 7 and 13mm placing a strong constraint on the nature of the variable emission. The hourly time scale variability can be explained in the context of a model in which the peak frequency of emission shifts toward lower frequencies as a self-absorbed synchrotron source expands adiabatically near the acceleration site. The short time scale variability, on the other hand, places a strong constraint on the size of the emitting region. Assuming that rapid minute time scale fluctuations of the emission is optically thick in radio wavelength, light travel arguments requires relativistic particle energy, thus suggesting the presence of outflow from SgrA*.