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Paper: Time Variations of the Sgr A* Flux at 230 GHz With ALMA
Volume: 528, New Horizons in Galactic Center Astronomy and Beyond
Page: 223
Authors: Iwata, Y.; Oka, T.; Miyoshi, M.; Tsuboi, M.; Takekawa, S.
Abstract: We found time variations of the Sgr A* flux at 230 GHz with the ALMA Cycle 5 observations. We used the phase-only self-calibration technique to reduce residual calibration errors. Measuring the flux density of Sgr A* in the snapshots of a 1-min bin, we obtained seven light curves with a 70-min duration. The light curves clearly show time variations with a time scale of a few tens of minutes, which is as short as the orbital period of the innermost stable circular orbit around a black hole with 4×106 M. Therefore, the observed millimeter emission is considered to have been occurred very close to the Galactic center black hole.
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