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

Abstract

We present the third MAXI/GSC catalog in the high Galactic latitude sky ( ) based on the 7-year data from 2009 August 13 to 2016 July 31, complementary to that in the low Galactic latitude sky ( ) (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.