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We present the second catalog of flaring gamma-ray sources (2FAV) detectedwith the Fermi All-sky Variability Analysis (FAVA), a tool that blindlysearches for transients over the entire sky observed by the Large AreaTelescope (LAT) on board the \textit{Fermi} Gamma-ray Space Telescope. Withrespect to the first FAVA catalog, this catalog benefits from a larger dataset, the latest LAT data release (Pass 8), as well as from an improved analysisthat includes likelihood techniques for a more precise localization of thetransients. Applying this analysis on the first 7.4 years of \textit{Fermi}observations, and in two separate energy bands 0.1$-$0.8 GeV and 0.8$-$300 GeV,a total of 4547 flares has been detected with a significance greater than$6\sigma$ (before trials), on the time scale of one week. Through spatialclustering of these flares, 518 variable gamma-ray sources are identified.Likely counterparts, based on positional coincidence, have been found for 441sources, mostly among the blazar class of active galactic nuclei. For 77 2FAVsources, no likely gamma-ray counterpart has been found. For each source in thecatalog, we provide the time, location, and spectrum of each flaring episode.Studying the spectra of the flares, we observe a harder-when-brighter behaviorfor flares associated with blazars, with the exception of BL Lac flaresdetected in the low-energy band. The photon indexes of the flares are neversignificantly smaller than 1.5. For a leptonic model, and under the assumptionof isotropy, this limit suggests that the spectrum of the freshly acceleratedelectrons is never harder than $p\sim$2.

The second catalog of flaring gamma-ray sources from the Fermi All-sky Variability Analysis