The Center of the Milky Way from Radio to X-rays

TL;DR

This paper reviews multi-wavelength observations of Sagittarius A*, focusing on the DSO/G2 object’s fly-by and its potential impact on the black hole's activity, providing new orbital estimates and insights into the system's stability.

Contribution

It offers new orbital parameters for the DSO/G2 object and assesses the stability of SgrA* through polarization and variability analysis, highlighting the potential for future activity due to the fly-by.

Findings

DSO/G2 passed periapse in May 2014 near SgrA*

SgrA* shows stable polarization and variability over years

No significant emission changes detected during the fly-by

Abstract

We summarize basic observational results on Sagittarius~A* obtained from the radio, infrared and X-ray domain. Infrared observations have revealed that a dusty S-cluster object (DSO/G2) passes by SgrA*, the central super-massive black hole of the Milky Way. It is still expected that this event will give rise to exceptionally intense activity in the entire electromagnetic spectrum. Based on February to September 2014 SINFONI observations. The detection of spatially compact and red-shifted hydrogen recombination line emission allows a us to obtain a new estimate of the orbital parameters of the DSO. We have not detected strong pre-pericenter blue-shifted or post-pericenter red-shifted emission above the noise level at the position of SgrA* or upstream the orbit. The periapse position was reached in May 2014. Our 2004-2012 infrared polarization statistics shows that SgrA* must be a very stable system - both in terms of geometrical orientation of a jet or accretion disk and in terms of the variability spectrum which must be linked to the accretion rate. Hence polarization and variability measurements are the ideal tool to probe for any change in the system as a function of the DSO/G2 fly-by. Due to the 2014 fly-by of the DSO, increased accretion activity of SgrA* may still be upcoming. Future observations of bright flares will improve the derivation of the spin and the inclination of the SMBH from NIR/sub-mm observations.