Suzaku spectroscopy of an X-ray reflection nebula and a new supernova remnant candidate in the Sgr B1 region

摘要

We made a 100 ks observation of the Sagittarius (Sgr) B1 region at (l, b) = (0.degrees 5, -0.degrees 1) near to the Galactic center (GC) with the Suzaku/XIS. Emission lines of S xv, Fe I, Fe XXV, and Fe XXVI were clearly detected in the spectrum. We found that the Fe XXV and Fe XXVI line emissions smoothly distribute over the Sgr B1 and B2 regions connecting from the GC. This result suggests that the GC hot plasma extends at least up to the Sgr B region with constant temperature. There are two diffuse X-ray sources in the observed region. One of the two (G0.42-0.04) is newly discovered, and exhibits a strong S xv K alpha emission line, suggesting a candidate for a supernova remnant located in the GC region. The other one (M 0.51-0.10), having a prominent Fe I Ka emission line and a strongly absorbed continuum, is likely to be an X-ray reflection nebula. There is no near source bright enough to irradiate M 0.51-0.10. However, the Fe I Ka emission can be explained if Sgr A* was similar to 10(6) times brighter 300 years ago, the light travel time for 100 pc to M 0.51-0.10, than it is at present.