What are X-ray bursts?

About X-ray bursts

• It occurs in low-mass X-ray binary systems where a neutron star and low-mass main sequence star are in orbit around one another.
• Due to their close proximity and the extreme gravity of the neutron star, the companion star overflows its roche-lobe and hydrogen is drawn into an accretion disk around the neutron star.
• This hydrogen is eventually deposited on the surface of the neutron star and immediately is converted into helium due to the extreme temperatures and pressures that exist there.
• A thin surface layer of helium is built up, and once a critical mass of helium is reached, it ignites explosively, heating the entire surface of the neutron star to several tens of millions of degrees releasing a sudden burst of X-rays.
• Once the outburst is over, the binary system temporarily returns to its quiescent state while the neutron star begins to re-accumulate the helium surface layer.
• The process repeats resulting in recurrent X-ray bursts.
• It generally occurs at regular intervals separated by several hours or days.

What is a magnetar?

• It is an exotic type of neutron star, its defining feature that it has an ultra-powerful magnetic field.
• The field is about 1,000 times stronger than a normal neutron star and about a trillion times stronger than the Earth’s.
• Apart from ultra-powerful magnetic fields, magnetars also release vast amounts of energy in the form of flares, X-rays, and gamma-ray bursts.
• They are therefore associated with extreme events in the universe, making them perhaps the most bizarre objects in the cosmos next to black holes.
• The magnetic field of a magnetar may be caused by a neutron star’s interior – thought to be made up of neutrons, quarks and exotic states of matter such as Bose-Einstein Condensates – becoming a superconducting fluid.

Q1) What is Helium (He)?

It is a chemical element, inert gas of Group 18 (noble gases) of the periodic table. The second lightest element (only hydrogen is lighter), helium is a colourless, odourless, and tasteless gas that becomes liquid at −268.9 °C (−452 °F). The boiling and freezing points of helium are lower than those of any other known substance.

Source: Milli-second burst detected by AstroSat in new high magnetic field neutron star can help understand such stellar entities