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The Galactic Center (GC) presents one of the highest stellar densities in ourGalaxy, making its surroundings an environment potentially rich in radiotransients, such as pulsars and different kinds of flaring activity. In thispaper, we present the first study of transient activity in the region of the GCbased on Atacama Large Millimeter/submillimeter (mm/submm) Array (ALMA)continuum observations at 230 GHz. This search is based on a newself-calibration algorithm, especially designed for variability detection inthe GC field. Using this method, we have performed a search of radio transientsin the effective field of view of~$\sim 30\,$arcseconds of the GC centralsupermassive black hole Sagittarius A* (SgrA*) using ALMA 230 GHz observationstaken during the 2017 Event Horizon Telescope (EHT) campaign, which spanseveral observing hours (5-10) on 2017 April 6, 7, and 11. This calibrationmethod allows one to disentangle the variability of unresolved SgrA* from anypotential transient emission in the wider field of view and residual effects ofthe imperfect data calibration. Hence, a robust statistical criterion toidentify real transients can be established: the event should survive at leastthree times the correlation time and it must have a peak excursion of at leastseven times the instantaneous root-mean-square between consecutive images. Ouralgorithms are successfully tested against realistic synthetic simulations oftransient sources in the GC field. Having checked the validity of thestatistical criterion, we provide upper limits for transient activity in theeffective field of view of the GC at 230 GHz.

A first search of transients in the Galactic Center from 230 GHz ALMA observations