A group of astronomers identified eight stars belonging to a rare type known as ‘MRPs,’ or Main-sequence Radio Pulse emitters, using the Giant Metrewave Radio Telescope (GMRT) in Pune.
The team of scientists, led by astronomers from the National Centre for Radio Astrophysics (NCRA) in Pune, identified a new type of radio star that is hotter than the Sun and has extraordinarily high magnetic fields and a significantly greater stellar wind.
The NCRA stated in a news statement that the researchers have previously detected three other similar stars using the GMRT. The GMRT was used to uncover 11 of the total 15 MRPs known so far, with eight of them detected in 2021 alone, owing to the enhanced GMRT’s broad bandwidth and great sensitivity.
‘These discoveries are the fruits of an ongoing survey with the GMRT, which was launched specifically for the purpose of solving the mystery of MRPs’, it said.
According to the NCRA, the success of the GMRT programme has revolutionised the idea of this class of stars and opened up a new window for studying their unusual magnetospheres.
As per the study, MRPs are stars that are hotter than the Sun and have extraordinarily powerful magnetic fields and stellar winds. As a result, they generate dazzling radio pulses, similar to a lighthouse. Though the first MRP was discovered in 2000, the number of such stars known has grown many times in recent years, thanks to the high sensitivity of the updated GMRT (uGMRT), with 11 of the 15 detected using the high-tech telescope, the NCRA stated.
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The success of the uGMRT study suggests that the prevailing perception of MRPs as rare items may not be accurate. Rather, they are likely more frequent, but tougher to detect. The radio pulses are only visible at particular times, and the phenomena is usually noticeable at low radio frequencies.
‘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 release said.
The uGMRT investigation allowed them to discover that the magnetic field and temperature are two variables that appear to have a big influence in determining the intensity of the radio pulse.
According to the announcement, a research study reporting these new findings was just approved for publication in ‘The Astrophysical Journal.’ Barnali Das, the study’s primary author, recently finished her PhD thesis at the National Centre for Radio Astrophysics, Tata Institute of Fundamental Research (NCRA-TIFR) in Pune, under the direction of Prof Poonam Chandra.
Das and Prof Chandra have worked on a number of studies targeted at characterising this little-known class of objects known as MRPs. The press statement said that they first used the term MRP in 2020.
For the first time, their research revealed that the radio pulses released by MRPs carry a wealth of information about the stellar magnetosphere.
They used two of the world’s finest radio telescopes, the GMRT and the US-based Karl G Jansky Very Large Array (VLA), to perform the most exhaustive investigation of MRPs over an ultra-wide frequency range in order to better understand their characteristics.
The GMRT is a radio telescope that operates between 150 and 1420 MHz and is located near Khodad, about 80 kilometres from Pune. It is operated by the NCRA-TIFR and comprises 30 antennas, each of 45m diametre.
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