| Name | Distance (kpc) | Binary Period (days) | Characteristics of X-rays | Characteristics of Visible Star/Companion |
| Cygnus X-1 | 2.5 | 5.6 | Vary in duration from 0.001 to 1 second | Blue supergiant of about 16 solar masses; 9 solar mass black hole |
| Centaurus X-3 | 6.1 | 2.087 | Eclipses with 0.488-day duration; pulses every 0.72 second | Blue giant of about 20 solar masses; 1.1-solar-mass neutron star |
| Small Magellanic Cloud X-1 | 66 | 3.89 | Eclipses with 0.6-day duration; pulses every 0.72 second | Blue supergiant of 17 solar masses; 1.1-solar-mass neutron star |
| Vela X-1 | 1.4 | 8.96 | Eclipses with 1.7-day duration; flares lasting a few hours | Blue supergiant of about 25 solar masses? |
| Hercules X-1 | 4.9 | 1.70 | Eclipses with 0.24-day duration; pulses every 1.24 seconds | Companion HZ Her, about 2.4 solar masses; 1.5-solar-mass neutron star |
| Scorpio X-1 | 0.7 | 0.787 | Vary in duration down to 1 second; no eclipses | Less than 2 solar masses; orbital period 0.78 days |