X-Ray Burster

X-Ray bursters are Binary Stars that act as a X-ray source and radiates thousands of times more energy than the Sun in short bursts that last only seconds. Astrophysicists suggest that a neutron star in a close binary star system accretes matter onto its surface from a companion until temperatures reach the level needed for hydrogen fusion to take place. This results in a sudden period of rapid nuclear burning and the subsequent release of an enormous quantity of energy. The gaseous matter pulled away from the companion star generally forms an accretion disk around the neutron star. Spiraling matter in the inner portions of the accretion disk becomes extremely hot, releasing a steady stream of X-rays.

As the inward flowing gas builds up on the neutron star’s surface, the temperature of the gas rises due to the pressure of overlying material. Eventually, the temperature of the captured material reaches thermonuclear fusion conditions. The result is a rapid period of thermonuclear hydrogen burning, a phenomenon that releases an enormous amount of energy, characterized by a burst of X-rays. Hours then pass as fresh new accreted material accumulates on the neutron star’s surface and conditions approach the production of another rapid X-ray burst.

Sometimes not all of the in-falling material from the stellar companion makes it to the surface of the nearby neutron star. In such cases a portion of the in-falling gaseous material is shot out into interstellar space at enormously high speeds in narrow jets. For example, astronomers have observed an interesting celestial object called SS 433. It is an eclipsing X-ray binary system that behaves as an X-ray burster. This compact object expels the equivalent of one Earth mass of material each year in two narrow jets that travel in opposite directions roughly perpendicular to an accretion disk. When these jets, traveling at about 80,000 km/s, or about 25 percent of the speed of light, interact with the interstellar medium, they emit radiation in the radio frequency portion of the electromagnetic spectrum.

Questions to Ponder

• How are X-ray busters different from Binary Systems?
• Are there X-ray bursters in the Milky way Galaxy? If so, name the one closest to the Earth.