Pune astronomers claim discovery of 8 MRP class of stars using GMRT

Updated on Nov 19, 2021 11:47 PM IST

The team of Pune astronomers had discovered three such stars in the past using the GMRT. Thus, of the total of 15 MRPs known so far, 11 were discovered with the GMRT, of which eight have been discovered in 2021 alone

A research paper describing the new discoveries by the astronomers in Pune has been accepted for publication in The Astrophysical Journal. (Pratham Gokhale/HT Photo)
A research paper describing the new discoveries by the astronomers in Pune has been accepted for publication in The Astrophysical Journal. (Pratham Gokhale/HT Photo)
ByDheeraj Bengrut

A group of astronomers at the National Centre for Radio Astrophysics (NCRA) in Pune claim to have discovered eight stars belonging to a rare class called “MRPs”, or, Main-sequence Radio Pulse Emitters.

The discovery was made using the Giant Metrewave Radio Telescope (GMRT) located near Pune.

The team had discovered three such stars in the past using the GMRT. Thus, of the total of 15 MRPs known so far, 11 were discovered with the GMRT, of which eight have been discovered in 2021 alone.

The bandwidth and high sensitivity of the upgraded GMRT is being cited as the key behind these discoveries.

A research paper describing the new discoveries has been accepted for publication in The Astrophysical Journal.

The lead author of the paper is Barnali Das, who recently completed a PhD, working under the supervision of Prof Poonam Chandra at the NCRA’s Tata Institute of Fundamental Research, Pune. Barnali Das and Prof Chandra have been actively involved in various projects aiming at the characterisation of this little-known class of MRPs.

“The MRPs are stars hotter than Sun with unusually strong magnetic fields, and much stronger stellar winds. Due to this, they emit bright radio pulses like a lighthouse. Though the first MRP was discovered in 2000, it was only due to the high sensitivity of the upgraded GMRT (uGMRT) that the number of such stars is known have increased many fold in recent years, with 11 of the 15 being discovered using the GMRT. The success of the survey with the uGMRT suggest that the current notion that MRPs are rare objects may not be correct,” said lead author Das.

In fact, the name MRP was introduced by them in the year 2020. In an effort to understand their properties, they have performed the most extensive study of MRPs over an ultra-wide frequency range, using two of the world’s leading radio telescopes: the GMRT and the US- based Karl G Jansky Very Large Array (VLA).

Their work, for the first time, showed that the radio pulses emitted by MRPs contain a vast amount of information regarding the stellar magnetosphere.

“The pulsed radio emission from MRPs are the only visible signatures of the theoretical models which predicts tiny explosions in magnetic massive stars which occur at specific locations in the magnetosphere of the star. These explosions have been predicted to play an important role in regulating the transport of wind materials surrounding the star, and are likely to affect the stellar evolution as well. The radio pulses produced by MRPs are the only probes that are sensitive enough to reflect the changes incurred by these relatively weak events. Further experiments are underway to characterize these changes in pulse-behavior so as to be able to use the radio pulses to study the dynamic stellar magnetospheres.” added Das.

Prof Chandra said, “This is the frequency range where the uGMRT stands out as the most sensitive telescope in the world. The high sensitivity of the uGMRT and its ability to make high-resolution images were instrumental in enabling the recovery of the pulsed signal from the different types of radiation coming from the sky. This, combined with a strategic observation campaign allowed the astronomers to overcome the difficulties, and reveal the true nature of these objects. The study with the uGMRT allowed us to find that the magnetic field and temperature are two quantities that appear to play the major role in deciding how intense the radio pulse will be. These findings will be crucial in understanding what switches off the production of radio pulses in a hot magnetic star.”

The GMRT is a radio telescope located at Khodad, 80 km away from Pune.

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