Indian scientists reveal hidden structure around a famous neutron star

Indian scientists at the Raman Research Institute have found that the bright X-ray pulsar Centaurus X-3 is accreting matter through an accretion disk, a rare phenomenon for such pulsars. The discovery was made through the study of secondary emission lines.

New Delhi: Indian scientists have discovered that one of the brightest X‑ray pulsars, Centaurus X‑3, is gobbling up material through an accretion disk — a rare behaviour for pulsars of its kind, an official statement said on Wednesday.

The finding was made by researchers at the Raman Research Institute (RRI), an autonomous institution of the Department of Science and Technology (DST), led by Kinjal Roy.

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The study has implications in developing better-informed models of the system, which is one of the most widely studied binary pulsars that has drawn the attention of scientists because of its intense brightness.

Further, it will lead to enhanced understanding of binary pulsars in general.

An X-ray binary pulsar consists of a pulsar— a highly magnetised neutron star, and a Sun-like star bound in a gravitational dance. A neutron star is a celestial body with the mass of our sun crunched into a ball the size of Bangalore.

“In an X-ray binary, the pulsar’s extreme gravity pulls in material ejected by its companion star, and the pulsar starts accreting material from it, shooting out X-rays in the process,” the statement from the Ministry of Science & Technology said.

Centaurus X-3, a high-mass X-ray binary (HMXB) where the companion is more than 10 times the Sun’s mass, was one of the first X-ray pulsars to be discovered, and the third X-ray source to be discovered in the constellation Centaurus, 24,000 light years away.

Pulsars emit radiation from their magnetic poles, known as the primary emission. As the pulsar spins, this radiation sweeps past any satellite waiting to detect it. This radiation also falls around the neutron star.

Structures in its wider environment absorb and re-emit this radiation, dubbed as the secondary radiation.

These structures help understand the system’s physical parameters, such as its orientation and magnetic field strength, leading to enhanced understanding of binary pulsars, the statement noted.

Scientists from the Raman Research Institute (RRI) investigated four secondary emission lines in depth and found that the structure responsible for the varying lines must be co-rotating with the pulsar.

Detection revealed an accretion stream, which is a structure that channels material from the accretion disk towards the pulsar, that is causing the variability in the secondary emission lines. An accretion stream proved the existence of an accretion disk, the ministry said.