Super heavyweight and flyweight in a cosmic dance
Voluntary distributed computer project [email protected] discovered Neutron star in an unusual binary system.
After more than two decades, an international research team headed by the Max Planck Institute for Gravitational Physics (Albert Einstein Institute; AEI) in Hanover has identified a galactic “mysterious source” of gamma rays: a heavy neutron star with a companion with a very small one Earth encircles it. Use of new data analysis methods, which are carried out on around 10,000 graphics cards in the distributed computer project [email protected]The team identified the neutron star on the basis of its regularly pulsing gamma rays during an intensive search for data NASAFermi satellite. Surprisingly, the neutron star is completely invisible in radio waves. The binary system was characterized with an observation campaign over the electromagnetic spectrum and breaks several records.
An odd couple set new records
“The binary star system and the neutron star in the heart, now known as PSR J1653-0158, set new records,” explains Lars Nieder, PhD student at AEI Hannover and first author of the study published today in Astrophysical diary letters. “We discovered the galactic dance of a super heavyweight with a flyweight: With a little more than twice the mass of our sun, the neutron star is extremely heavy. Its companion has about six times the density of lead, but only about 1% of the mass of our sun. This “strange pair” orbits faster than any known comparable binaries every 75 minutes. ”
Representation of the binary star system with the pulsar J1653-0158 (below) compared to the Earth-Moon system (above). All objects and orbits are shown to scale, with the exception of the pulsar, which is enlarged 450 times. The binary star system with an orbital time of only 75 minutes is only slightly larger than the earth-moon system. Photo credits: Knispel / Clark / Max Planck Institute for Gravitational Physics / NASA
The neutron star also rotates around its own axis at more than 30,000 rpm, making it one of the fastest rotating. At the same time, its magnetic field – usually extremely strong in neutron stars – is exceptionally weak. This record recognition was made possible through two important steps.
Step 1: Observe at many wavelengths
Astronomical observations made in 2014 made it possible to determine the properties of the binary star’s orbits.
“Since 2009, it has been considered likely that a neutron star is located behind the gamma ray source that has been known since 1999. In 2014, after observing the system with optical and X-ray telescopes, it became clear that this is a very tight binary system. However, all searches for the neutron star it contains have so far been in vain, ”says Dr. Colin Clark from the Jodrell Bank Center for Astrophysics, co-author of the study and former doctoral student at AEI Hannover.
Step 2: Use of the donated computing power [email protected]
In order to clearly prove the existence of a neutron star, not only its radio waves or gamma rays, but also their characteristic pulsations must be recorded. The rotation of the neutron star causes this regular blinking, similar to the periodic twinkling of a distant lighthouse. The neutron star is then referred to as a radio or gamma ray pulsar, respectively.
“In binary systems like the one we have just discovered, pulsars are called ‘black widows’ because they eat their partners, so to speak, like spiders of the same name,” explains Clark. He adds: “The pulsar evaporates its companion with its radiation and a particle wind and fills the star system with it plasma that is impenetrable to radio waves. ”
Gamma rays, on the other hand, are not stopped by these plasma clouds. The Large Area Telescope (LAT) on board NASA’s Fermi gamma-ray space telescope records this radiation.
The team used the data from 2014, further observations with the William Herschel telescope on La Palma and the exact sky position determined by the Gaia satellite to determine and focus the computing power of the voluntary distributed computer project [email protected] This also provided a more complete sketch of the companion star.
Finding a very tight binary system with improved analysis
They improved on earlier methods developed for this purpose and asked tens of thousands of volunteers to help search through archive data from the Fermi LAT for periodic pulsations for about a decade or so. The volunteers donated idle computing cycles on the graphics cards (GPUs) of their computers [email protected] In less than two weeks, the team made a discovery that would have taken centuries on a conventional computer.
The entire sky as seen from the Fermi Gamma-Ray Space Telescope and discovered the new pulsar of [email protected] The field below the enlarged inset shows the pulsar name and some of its measured properties, as well as its gamma ray pulsations. The flags show the nationalities of the volunteers whose computers found the pulsar. Photo credits: Knispel / Max Planck Institute for Gravitational Physics / NASA / DOE / Fermi LAT collaboration
“We found a very tight binary system. In its center is the pulsar, which is around 20 kilometers in size and twice the mass of our sun. The rest of a dwarf star orbits the pulsar at a distance of only 1.3 times the earth-moon distance in just 75 minutes at a speed of more than 700 kilometers per second, ”explains Nieder. “This unusual duo could have originated from an extremely tight binary system in which matter originally flowed from the companion star to the neutron star, increasing its mass and making it rotate faster and faster while at the same time its magnetic field was dampened.”
Search for radio and gravitational waves
After the team identified the gamma-ray pulsar, they used their newfound knowledge and searched for its radio waves again. They found no trace, although they used the largest and most sensitive radio telescopes in the world. PSR J1653-0158 thus becomes the second fast rotating pulsar from which no radio waves are seen. There are two possible explanations: either the pulsar is not sending radio waves to Earth or, more likely, the plasma cloud envelops the binary star system so completely that radio waves do not reach Earth.
In a further step, they looked for data from the first and second observation run of the Advanced LIGO Detectors for possible Gravitational waves that the neutron star would emit if it were slightly deformed. Here too the search was unsuccessful.
Exciting future
“The catalog of gamma-ray sources found by the Fermi satellite contains dozens more that I would bet contain binary pulsars,” says Prof. Bruce Allen, director at the Max Planck Institute for Gravitational Physics in Hanover and director and founder of [email protected] “So far, however, nobody has been able to determine the characteristic pulsation of their gamma rays. With [email protected]We hope to do just that – who knows what other surprises are waiting for us. ”
background information
Who made the discovery? The discovery was made possible by tens of thousands of [email protected] Volunteers who donated their CPU and GPU time to the project. Without them, this study could not have been conducted and this discovery could not have been made. The team is particularly grateful to the volunteers whose computers discovered the pulsar: Yi-Sheng Wu from Taoyuan, Taiwan, and Daniel Scott from Ankeny, Iowa, USA.
Neutron stars are compact remnants of supernova explosions and consist of exotic, extremely dense matter. They are around 20 kilometers in diameter and weigh more than our sun. Due to their strong magnetic fields and rapid rotation, they emit radiant radio waves and energetic gamma rays that resemble a cosmic lighthouse. When these rays point to Earth as the neutron star rotates, it becomes visible as a pulsating radio or gamma ray source – a so-called pulsar.
