On 2009 June 5 , the Gamma-ray Burst Monitor ( GBM ) onboard the Fermi Gamma-ray Space Telescope triggered on two short , and relatively dim bursts with spectral properties similar to Soft Gamma Repeater ( SGR ) bursts .
Independent localizations of the bursts by triangulation with the Konus-RF and with the Swift satellite , confirmed their origin from the same , previously unknown , source .
The subsequent discovery of X-ray pulsations with the Rossi X-ray Timing Explorer ( RXTE ) , confirmed the magnetar nature of the new source , SGR J 0418 + 5729 .
We describe here the Fermi /GBM observations , the discovery and the localization of this new SGR , and our infrared and Chandra X-ray observations .
We also present a detailed temporal and spectral study of the two GBM bursts .
SGR J 0418 + 5729 Â is the second source discovered in the same region of the sky in the last year , the other one being SGRÂ J 0501 + 4516 .
Both sources lie in the direction of the galactic anti-center and presumably at the nearby distance of \sim 2 kpc ( assuming they reside in the Perseus arm of our galaxy ) .
The near-threshold GBM detection of bursts from SGR J 0418 + 5729 Â suggests that there may be more such “ dim ” SGRs throughout our galaxy , possibly exceeding the population of “ bright ” SGRs .
Finally , using sample statistics , we conclude that the implications of the new SGR discovery on the number of observable active magnetars in our galaxy at any given time is \lesssim 10 , in agreement with our earlier estimates .