A team of astronomers from the Pune-based National Centre for Radio Astrophysics (NCRA-TIFR) used the upgraded Giant Metrewave Radio Telescope (uGMRT) to discover eight stars belonging to a rare category known as “Main-sequence Radio Pulse” emitters, or MRPs, which will aid in the understanding of “exotic” radio stars and stellar magnetospheres.
Because of the wide bandwidth and high sensitivity of the upgraded GMRT, which is a radio telescope located at Khodad in the Pune district and is not operated by the National Radio Astronomy Observatory in the United States, 11 MRPs have been discovered by the NCRA-TIFR team alone (with three MRPs spotted in the recent past).
The MRPs are stars with magnetic fields that are substantially stronger than stellar wind (a continuous flow of gas from a star’s upper atmosphere) and are far hotter than the Sun. As a result, they generate intense radio pulses, similar to a lighthouse.
“The GMRT program’s success has changed our perceptions of this group of stars.” Though the first MRP was identified in 2000, it was only because of the uGMRT’s great sensitivity that other such stars could be located. The survey’s success suggests that the existing perception of MRPs as uncommon things may be incorrect. Rather, they are likely more prevalent but harder to identify, “says Barnali Das, a PhD student at the NCRA-TIFR who has been researching this phenomenon.
Last year, Ms. Das and her supervisor, Prof. Poonam Chandra of the NCRA, were the ones who initially coined the term “MRP” to describe the features of these stars. Using two of the world’s best radio telescopes, the uGMRT and the Karl G. Jansky Very Large Array in the United States, the duo has conducted the most extensive research of MRPs across an ultra-wide frequency range (VLA).
Prof. Chandra claims that the difficulty in detecting MRPs stems from the fact that radio pulses are only detectable at certain periods and the phenomena is usually noticeable at low radio frequencies.
“The uGMRT’s great sensitivity and capacity to produce high-resolution pictures were critical in allowing the pulsed signal to be recovered from the many forms of radiation coming from the sky.” This, paired with a well-planned observation campaign, allowed the astronomers to overcome challenges and disclose the real nature of these objects. “We discovered that magnetic fields and temperature seem to have a big influence in determining the intensity of the radio pulse,” she says.
These discoveries will be significant in determining what causes a hot magnetic star to stop producing radio pulses.
The prestigious Astrophysical Journal has approved a research article reporting these new results for publication (ApJ).
For the first time, Ms. Das, Prof. Chandra, and other NCRA team members have shown that the radio pulses released by MRPs contain a wealth of information about the stellar magnetosphere.
“The pulsed radio emission from MRPs is the sole apparent trace of theoretical models that anticipate small explosions in magnetic massive stars at specified regions in the star’s magnetosphere.” “These explosions are expected to play a key role in controlling the flow of wind elements around the star, as well as having an impact on stellar development,” Ms. Das says.
Source: The Hindu