The 7-year MAXI/GSC X-Ray Source Catalog in the High Galactic Latitude Sky (3MAXI)

We present the third MAXI/GSC catalog in the high Galactic latitude sky (| b| > 10^\circ ) based on the 7-year data from 2009 August 13 to 2016 July 31, complementary to that in the low Galactic latitude sky (| b| < 10^\circ ) (Hori et al. 2018). We compile 682 sources detected at significances of s _{D,4-10 keV} ≥ 6.5 in the 4-10 keV band. A two-dimensional image fit based on the Poisson likelihood algorithm (C-statistics) is adopted for the detections and constraints on their fluxes and positions. The 4-10 keV sensitivity reaches ≈0.48 mCrab, or ≈5.9 × 10^-12 erg cm^-2 s^-1, over half of the survey area. Compared with the 37-month Hiroi et al. (2013) catalog, which adopted a threshold of s _{D,4-10 keV} ≥ 7, the source number increases by a factor of ∼1.4. The fluxes in the 3-4 keV and 10-20 keV bands are further estimated, and hardness ratios (HRs) are calculated using the 3-4 keV, 4-10 keV, 3-10 keV, and 10-20 keV band fluxes. We also make the 4-10 keV light curves in 1-year bins for all the sources and characterize their variabilities with an index based on a likelihood function and the excess variance. Possible counterparts are found from five major X-ray survey catalogs by Swift, Uhuru, RXTE, XMM-Newton, and ROSAT, as well as an X-ray galaxy cluster catalog (MCXC). Our catalog provides the fluxes, positions, detection significances, HRs, 1-year bin light curves, variability indices, and counterpart candidates.