What are X-ray bursts?

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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