Investigating the spectral and temporal characteristics of the X-rays coming from Sagittarius A* ( Sgr A* ) is essential to our development of a more complete understanding of the emission mechanisms in this supermassive black hole located at the center of our Galaxy .
Several X-ray flares with varying durations and spectral features have already been observed from this object .
Here we present the results of two long XMM-Newton observations of the Galactic nucleus carried out in 2004 , for a total exposure time of nearly 500 \mathrm { ks } .
During these observations we detected two flares from Sgr A* with peak 2–10 \mathrm { keV } luminosities about 40 times ( L _ { X } \sim 9 \times 10 ^ { 34 } erg s ^ { -1 } ) above the quiescent luminosity : one on 2004 March 31 and another on 2004 August 31 .
The first flare lasted about 2.5 ks and the second about 5 \mathrm { ks } .
The combined fit on the Epic spectra yield photon indeces of about 1.5 and 1.9 for the first and second flare respectively .
This hard photon index strongly suggests the presence of an important population of non-thermal electrons during the event and supports the view that the majority of flaring events tend to be hard and not very luminous .