Context : Stellar dynamics indicate the presence of a super massive 3–4 \times 10 ^ { 6 } M _ { \odot } Â Â black hole at the Galactic Center .
It is associated with the variable radio , near-infrared , and X-ray counterpart Sagittarius A* ( SgrA* ) .

Aims : The goal is the investigation and understanding of the physical processes responsible for the variable emission from SgrA* .

Methods : The observations have been carried out using the NACO adaptive optics ( AO ) instrument at the European Southern Observatory ’ s Very Large Telescope ( July 2005 , May 2007 ) and the ACIS-I instrument aboard the Chandra X-ray Observatory ( July 2005 ) .

Results : We find that for the July 2005 flare the variable and polarized NIR emission of SgrA* occurred synchronous with a moderately bright flare event in the X-ray domain with an excess 2 - 8 keV luminosity of about 8 \times 10 ^ { 33 } Â erg/s .
We find no time lag between the flare events in the two wavelength bands with a lower limit of \leq 10Â minutes .
The May 2007 flare shows the highest sub-flare to flare contrast observed until now .
It provides evidence for a variation in the profile of consecutive sub-flares .

Conclusions : We confirm that highly variable and NIR polarized flare emission is non-thermal and that there exists a class of synchronous NIR/X-ray flares .
We find that the flaring state can be explained via the synchrotron self-Compton ( SSC ) process involving up-scattered sub-millimeter photons from a compact source component .
The observations can be interpreted in a model involving a temporary disk with a short jet .
In the disk component the flux density variations can be explained by spots on relativistic orbits around the central super massive black hole ( SMBH ) .
The profile variations for the May 2007 flare are interpreted as a variation of the spot structure due to differential rotation within the disk .