More than two decades later, an international research team has identified a mysterious galactic gamma-ray source: a heavy neutron star with a low-mass companion orbiting it.
Using new data analysis techniques running on about 10,000 graphics maps as part of the distributed civil science project Einstein @ Home, the team identified a neutron star from its regularly pulsating gamma rays through in-depth analysis of Fermi data. Surprisingly, the neutron star is completely invisible in radio waves. The binary system has been characterized in a campaign of observations across the entire electromagnetic spectrum and has broken several records.
The neutron star also revolves around its axis at over 30,000 rpm, making it one of the fastest spinning stars. At the same time, its magnetic field – usually extremely strong in neutron stars – is extremely weak. Astronomical observations in 2014 made it possible to determine the properties of the binary star's orbits.
'That a neutron star is behind a gamma-ray source known since 1999 has been considered likely since 2009. In 2014, after observing the system with optical and X-ray telescopes, it became clear that this is a very dense binary system. But all searches for a neutron star have so far failed, '' said study co-author Dr. Colin Clark of the Jodrell Bank Center for Astrophysics at the University of Manchester.
To unambiguously prove the existence of a neutron star, it is necessary to detect not only its radio waves or gamma rays, but also their characteristic pulsations. The spin of the neutron star causes this regular twinkling, similar to the periodic twinkling of a distant beacon. In this case, a neutron star is called a radio or a gamma pulsar, respectively.
The mystery of the unusual neutron star system has been revealed 20 years later thanks to thousands of volunteers. The new study, published today in the Astrophysical Journal Letters, is made possible by computer support from 10,000 volunteers.
Volunteers donated idle cycles on the graphics cards (GPUs) of their computers to Einstein @ Home. In less than two weeks, the team made a discovery that would have taken centuries to compute on a conventional computer.
After identifying the gamma pulsar, the team searched for its radio waves. They found no trace, although they used the largest and most sensitive radio telescopes in the world, including the Lovell Jodrell Bank Telescope. Thus, PSR J1653-0158 becomes the second rapidly rotating pulsar from which no radio waves are visible.
At the moment, there are two possible explanations: either the pulsar does not send radio waves to Earth, or, more likely, the plasma cloud envelops the binary star system so completely that no radio waves reach Earth.
In the next step, they searched the data from the first and second observation sessions using the Advanced LIGO detectors for possible gravitational waves that a neutron star would emit if it were slightly deformed. But the search was again unsuccessful.
