Some Binary X-ray Sources



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