Fermi Gamma-ray Space Telescope

Second Fermi All-sky Variability Analysis Catalog (2FAV)

The Fermi All-sky Variability Analysis (FAVA) is an analysis technique that searches for flaring sources in data collected by the Large Area Telescope (LAT) onboard NASA's Fermi Gamma-ray Space Telescope. It uses a photometric approach to blindly search for flares over the entire sky, and a likelihood analysis to precisely locate them and to measure their spectra.

This catalog contains the flares and sources detected by running FAVA over the first 7.4 years of Fermi mission, from Modified Julian Date (MJD) 54682 (2008-08-04) to 57391 (2016-01-04). The analysis has been run in weekly time bin and in two independent energy bands, 100-800 MeV and 0.8-300 GeV. The detection threshold applied to the catalog flares is equivalent to 6 sigma (pre trials).

The sources in the 2FAV are identified as clusters of flares. Their position and the corresponding error are derived from a weighted average of the best localized flares in the cluster. Likely gamma-ray counterparts, based on positional coincidence, are provided for the sources. For the flares, this catalog provides, together with the time and location information, the parameters of power-law fits to the source spectra in the two energy bands.

For a full description of the catalog see the LAT 2FAV Catalog Paper draft on the arXiv.

2FAV Catalog and Associated Products

The Second FAVA Catalog is available as a FITS file. Supporting files and associated products have been provided and are linked below.

  • Main FAVA Catalog file (FITS file) and column descriptions
  • 2FAV Catalog Paper draft
  • Searchable FAVA Catalog (BROWSE table)
  • DS9 region file for the catalog sources
  • DS9 region file for the catalog flares
  • Average sensitivity maps These maps shows the minimum flux increase, in a one week time bins and assuming and average exposure, that corresponds to a significance (from FAVA photometric analysis only) greater than 6σ in one of the two energy bands or greater than 4σ in both energy bands simultaneously.


    • These maps are computed assuming the average weekly exposure as derived from the 7.4 years covered by the 2FAV. The variations of the weekly exposure are not considered.
    • The sensitivity shown does not account for the more sensitive (~10-25% higher significances on average) likelihood follow up analysis that is used as a second stage in the 2FAV.
    • The maps are computed assuming a power-law spectrum for the flaring source, for two reference values of the photon index: 1.5 and 3.5.
    Please refer to the publication for further details.

2FAV Associated Pages

Second FAVA Catalog Change Log

Rev Date Filename Change Description
1 12 Dec 2016 2fav_v09.fits Initial release (deprecated 2FAV ids).
2 18 Jul 2017 2fav_v10.fits Official release.