Context: AstroSat, India’s first multi-wavelength space-based observatory, has detected bright sub-second X-ray bursts from a new and unique neutron star with ultrahigh magnetic field (magnetar), which can help understand the intriguing extreme astrophysical conditions of magnetars.

Magnetars

• They are neutron stars having an ultrahigh magnetic field that are much stronger than the terrestrial magnetic field.
• Simply put, the magnetic field of a magnetar is over one quadrillion time stronger than the magnetic field of Earth.
• What powers the emission of high-energy electromagnetic radiation in them is the decay of magnetic fields in these objects.
• Besides, magnetars display strong temporal variability, typically including a slow rotation, a rapid spin-down, bright but short bursts going on upto months-long outbursts.

X-ray bursts

They occur 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.

AstroSat

• It is India's inaugural dedicated multi-wavelength space observatory, representing the country's primary astronomy mission designed for the simultaneous study of celestial Sources in X-ray, optical, and UV spectral bands.

Launched on September 28, 2015, by the Indian launch vehicle PSLV from the Satish Dhawan Space Centre, Sriharikota, the observatory has a lift-off mass of 1515 kg and operates in a 650 km orbit inclined at an angle of 6 degrees to the equator.