See http : //www.xassist.org/ixocat_hri for figures and future updates of this catalog .
NOTE – some IXO numbers have changed since the original astro-ph submission .
This paper is now accepted into the ApJ Supplements , and Tables 1 and 2 comprise version 2.0 of our ROSAT HRI IXO catalog . ROSAT , and now Chandra , X-ray images allow studies of extranuclear X-ray point sources in galaxies other than our own .
X-ray observations of normal galaxies with ROSAT and Chandra have revealed that off-nuclear , compact , Intermediate-luminosity ( L _ { X } [ 2 - 10 ~ { } { keV } ] \geq 10 ^ { 39.0 } erg s ^ { -1 } ) X-ray Objects ( IXOs , a.k.a .
ULXs [ Ultraluminous X-ray sources ] ) are quite common .
Here we present a catalog and finding charts for 87 IXOs in 54 galaxies , derived from all of the ROSAT HRI imaging data for galaxies with cz \leq 5000 km s ^ { -1 } from the Third Reference Catalog of Bright Galaxies ( RC3 ) .
We have defined the cutoff L _ { X } for IXOs so that it is well above the Eddington luminosity of a 1.4 M _ { \odot } black hole ( 10 ^ { 38.3 } erg s ^ { -1 } ) , so as not to confuse IXOs with “ normal ” black hole X-ray binaries .
This catalog is intended to provide a baseline for follow-up work with Chandra and XMM , and with space- and ground-based survey work at wavelengths other than X-ray .
We demonstrate that elliptical galaxies with IXOs have a larger number of IXOs per galaxy than non-elliptical galaxies with IXOs , and note that they are not likely to be merely high-mass X-ray binaries with beamed X-ray emission , as may be the case for IXOs in starburst galaxies .
Approximately half of the IXOs with multiple observations show X-ray variability , and many ( 19 ) of the IXOs have faint optical counterparts in DSS optical B-band images .
Follow-up observations of these objects should be helpful in identifying their nature .