An international research group led by the Hannover-based Max Planck Institute for Gravitational Physics found that the J0952-0607 radio pulsar also emits pulsed gamma radiation. J0952-0607 spins 707 times in a second. This remains second in the list of fast-paced neutron stars. By analyzing about 8.5 years’ worth of data from NASA’s Fermi Gamma-ray Space Telescope, LOFAR radio observations from the past two years, observations from two large optical telescopes, and gravitational-wave data from the LIGO detectors, the team used approach to study the binary system of the pulsar and its lightweight companion in detail.
The gamma radiation of millisecond pulsar PSR J0952−0607 is so weak, it requires some smart, innovative exploration techniques to be detected-and these enabled original star measurements.
Pulsars are a type of dead star called neutron stars, the end result of a star that’s too massive to become a white dwarf, and not extensive enough to become a black hole. But the rotation of these pulsars is such that, as they spin, they sweep Earth with a beam of radiation, sometimes on timescales, so that are so precise they can help us measure the Universe.
Some of these pulsars are rotating so fast, and they go round on millisecond scales; fittingly, we call those millisecond pulsars, and they are usually found with a binary companion. It’s thought that their rotation speeds up as they absorb material away from that companion.
Pulsars are the compact remains of stellar explosions that have strong magnetic fields and are rapidly rotating. They emit radiation like a cosmic lighthouse and can be observable as radio pulsars and gamma-ray pulsars depending on their bearings towards Earth.
As per the official Fermi website in 2016, 17 percent of millisecond pulsars have been detected emitting gamma rays, compared to just 3 percent of the average pulsar population.
But PSR J0952−0607 is one of the most extreme yet, second only to PSR J1748-2446ad, discovered in 2006 to be rocketing around at 716 rotations per second.
It’s also what we term a “black widow”. The pulsar is 1.4 times the mass of the Sun, squished down into that teeny tiny diameter, with a binary companion around 0.02 times the mass of the Sun. What makes it a black widow is that insanely low binary companion mass: the pulsar has slurped up most of its companion. When the pulsar was discovered in 2017 earlier, there were no gamma rays detected emanating from the pulsars. The pulsar in itself was found using the Low-Frequency Array (LOFAR) radio telescope. This search for gamma-ray emissions was conducted using the robust Atlas Computing Cluster. And it found the signal – but something, Nieder said, was awry.
No gamma-ray pulsations before July 2011:
The news then came with another surprise that it was impossible to detect gamma-ray pulsations from the pulsar in the data from before July 2011. The reason for why the pulsar only seems to show pulsations after that date remains unknown. Variations in how much gamma rays it emitted might be one reason, but the pulsar is so faint that it was not possible to test this hypothesis with sufficient accuracy. Changes in the pulsar orbit seen in similar systems might also explain, but there was not even a hint in the data that this was happening.
Journal Reference: The Astrophysical Journal.