VITAL SIGNALS detected by the Pune-based Giant Meterwave Radio Telescope (GMRT) have helped capture the neutron star merger event, which emitted both gravitational and electromagnetic waves, as reported in August this year. The findings, made at the lowest sub-Ghz frequencies range, was majorly contributed by the GMRT, along with the Karl G Jansky Very Large Array observatory in New Mexico, US, and the Australia Telescope Compact Array in Narrabri.
Initially, scientists had presumed the event to be a super fast jet but have now concluded it to be a bubble-like cocoon in structure. A study, titled ‘A mildly relativistic wide-angle outflow in the neutron star merger GW170817’, was recently published in the online issue of Nature on Wednesday. Conducted using GMRT detections, the study revealed that the August event was similar to the jet dumping its energy into the cocoon structure, which was being pumped-in all energies.
Scientists from the two teams of the National Centre for Radio Astrophysics (NCRA), who have been observing the event along with their international counterparts, said, “The radio emissions, detected 16 days after August 17 seems to be increasing in its strength as per observations till December 2. This slow brightening of the radio light indicates the presence of a cocoon, which, due to its structure, is emitting more radio light than faster moving sharply focused jet material.”
Gamma Ray Bursts (GRB) usually signify the birth of the black hole, and, in this case, both telescopes — NASA’s Fermi Gamma-ray Space Telescope and the European International Gamma-Ray Astrophysicals Laboratory (INTEGRAL) — detected gamma ray bursts after the collision between the two neutron stars. However, these detections were very weak, making experts believe it to be short GRB (sGRB).
NCRA scientist Poonam Chandra said, “It was for the first time that both gravitational and electromagnetic waves were simultaneously detected. It is a moment of pride for the Indian astronomy, as GMRT managed to detect the signals even from the lowest possible frequencies.”
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