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We report the detection and analysis of a radio flare observed on 17 April2014 from Sgr A* at $9$ GHz using the VLA in its A-array configuration. This isthe first reported simultaneous radio observation of Sgr A* across $16$frequency windows between $8$ and $10$ GHz. We cross correlate the lowest andhighest spectral windows centered at $8.0$ and $9.9$ GHz, respectively, andfind the $8.0$ GHz light curve lagging $18.37^{+2.17}_{-2.18}$ minutes behindthe $9.9$ GHz light curve. This is the first time lag found in Sgr A*'s lightcurve across a narrow radio frequency bandwidth. We separate the quiescent andflaring components of Sgr A* via flux offsets at each spectral window. Theemission is consistent with an adiabatically-expanding synchrotron plasma,which we fit to the light curves to characterize the two components. Theflaring emission has an equipartition magnetic field strength of $2.2$ Gauss,size of $14$ Schwarzschild radii, average speed of $12000$ km s$^{-1}$, andelectron energy spectrum index ($N(E)\propto E^{-p}$), $p = 0.18$. The peakflare flux at $10$ GHz is approximately $25$% of the quiescent emission. Thisflare is abnormal as the inferred magnetic field strength and size aretypically about $10$ Gauss and few Schwarzschild radii. The properties of thisflare are consistent with a transient warm spot in the accretion flow at adistance of $10$-$100$ Schwarzschild radii from Sgr A*. Our analysis allows forindependent characterization of the variable and quiescent components, which issignificant for studying temporal variations in these components.

Detection of a 20 minute time lag observed from Sgr A* between 8 and 10 GHz with the VLA