Chandra Observation of Point Sources in the X-Ray Elliptical Galaxy NGC 1407

摘要

With the Chandra pointing observation of about 50 ks,we have detected 41 point sources in the X-ray relatively faint elliptical galaxy NGC 1407,most of which appear to be low mass X-ray binaries.In luminosity flux units,these resolved point sources contribute about 17.8% of the total emission of the galaxy in 0.3-10 keV.Of the remaining diffuse emission,about 53.4%(or 43.9% of total)may arise from unresolved point sources.We find six ultraluminous X-ray sources with luminosities above 1039 erg s-1.This number is less than has been found in NGC 720,but more than in NGC4697 and NGC 1553,so suggesting a possible correlation between the number of ULXs and the total X-ray luminosity of early-type galaxies.A central point-like source is detected whose luminosity(2.36 ± 0.14 × 1039 erg s-1)is the highest among all resolved sources.However,because of its relatively low hardness ratio,we speculate that it is not likely to be a low luminosity AGN.