The Long‐Term Variability of the X‐Ray Sources in NGC 6946 and NGC 4485/4490

• DOI: 10.1086/588817
• Publication Date: 2008-07-31T16:20:33Z
• Authors: Joel K. Fridriksson; Jeroen Homan; Walter H. G. Lewin; Albert K. H. Kong; David Pooley
• Keywords: Hubble sequence

We analyze data from five Chandra observations of the spiral galaxy NGC 6946 and three irregular/spiral interacting pair 4485/4490, with an emphasis on investigating long-term variability exhibited by source populations. detect 90 point sources coincident down to luminosities a few times 10^36 erg/s, 38 4485/90 luminosity ~1x10^37 erg/s. Twenty-five (15) in (NGC 4485/90) exhibit (i.e., weeks years) luminosity; 11 (4) are transient candidates. The single ultraluminous X-ray (ULX) all but one eight ULXs flux variability. Two have not been identified before as sources. widespread both systems is indicative populations being dominated binaries, this supported colors distribution among indicates large fraction high-mass binaries systems. shapes functions galaxies do change significantly between can be described power laws cumulative slopes ~0.6-0.7 6946) ~0.4 4485/90).