A Self-Consistent Model for the Broadband Spectrum of Sagittarius A Eastat the Galactic Center

Sgr A East is a very prominent elongated shell structure surrounding (thoughoff-centered from) the Galactic nucleus. Its energetics (~4x10^52 ergs), basedon the power required to carve out the radio synchrotron remnant within thesurrounding dense molecular cloud, appear to be extreme compared to the totalenergy (~10^51 ergs) released in a typical supernova (SN) explosion. Yet itshares several characteristics in common with SN remnants (SNRs), the mostsignificant of which is the ~0.1-10 GeV gamma-ray spectrum measured by EGRET,if we associate the Galactic center source 2EGJ1746-2852 with this nonthermalshell. We here show that the highest-energy component in Sgr A East's spectrum,like that of SNRs, can be fitted with the gamma-rays produced in neutral piondecays. Further, we demonstrate in a self-consistent manner that the leptonsreleased in the associated charged pion decays produce an e+e- distributionthat can mimic a power-law with index ~3, like that inferred from the VLA datafor this source. These relativistic electrons and positrons also radiate bybremsstrahlung, and inverse Compton scattering with the intense IR and UVfields from the nucleus. We show that the overall emissivity calculated in thisway may account for Sgr A East's broadband spectrum ranging from GHzfrequencies all the way to TeV energies, where Whipple has thus far set anupper limit to the flux corresponding to a 2.5-sigma signal above the noise.Comment: 14 pages, including 3 eps figures, LaTeX using aasms4.sty, accepted for publication in Astrophysical Journal Letters Replacement includes additional referenc