A group led by scientists from the RIKEN Cluster for Pioneering Research, using coordinated observations of the Crab Pulsar In a number of frequencies, they have found that the “giant radio pulses” they emit include an increase in X-ray emissions in addition to previously observed radio and visible light emissions. This finding, published in Science, implies that these impulses are hundreds of times more energetic than previously thought and could provide information about the mysterious phenomenon of “rapid radio explosions (FRB)”.
Giant radio pulses – a phenomenon in which extremely short millisecond radio pulses are emitted – have been observed in association with a dozen pulsars in our galaxy, but little is known about the mechanism that causes them. It has been proposed that these may also be the origin of “rapid radio explosions” – rapid explosions of radio waves believed to come from energy events in the extragalactic universe.
To obtain information about these phenomena, the group led by RIKEN made coordinated observations of the Crab pulsar, one of the most famous and best observed pulsars. The explosion of this star in a supernova explosion was witnessed by Chinese and Japanese observers in 1054 and led to the formation of the beautiful Crab Nebula that can be seen today.
This new multi-wavelength image of the Crab Nebula combines X-ray light from the Chandra X-ray Observatory (in blue) with visible light from the Hubble Space Telescope (yellow) and infrared light seen by the Spitzer Space Telescope (in red). ). This special combination of light from the electromagnetic spectrum highlights the nesting structure of the pulsar wind nebula. Credit: NASA, ESA, J. DePasquale (STScI) and R. Hurt (Caltech / IPAC)
The group began looking into whether there was an increase in X-ray emissions associated with giant radio pulses. In fact, despite numerous observations over several decades, researchers have so far been unable to make any unambiguous detection. The observations were based on an international campaign coordinated by simultaneous X-ray and ground-based radio observations, with space observations made with NICER, a new instrument placed aboard the International Space Station, and radio observations made by two observatories in Japan.
Over a three-year period, the group continued the campaign and eventually found a clear signal, exceeding five signs, indicating an increase in X-ray emissions associated with the increase in radio wavelength.
Between 2017 and 2019, the Neutron star NASA Composition Explorer (NICER) and NASA radio telescopes in Japan studied the Crab pulsar at the same time. In this view, which represents only 13 minutes of NICER observations, millions of X-rays are plotted against the pulsar’s rotational phase, which is centered on the strongest radio emission. For clarity, two full rotations are displayed. As pulsating beams pass through our line of sight, they produce two peaks for each rotation, the brightest being associated with a larger number of giant radio pulses. For the first time, NICER data show a slight increase in X-ray emissions associated with these events. Credit: NASA’s Goddard Space Flight Center / Enoto et al. 2021
The improved emission detected in the X-ray band was similar to that previously reported in the visible band, but nothing similar was ever observed from any of the other 2,800 known pulsars. According to Teruaki Enoto, the leader of the extreme natural phenomena RIKEN Hakubi Research Ream, “our measurements imply that these huge impulses are hundreds of times more energetic than previously thought.”
Another important effect of the discovery is that it places significant constraints on models of the mysterious phenomenon known as “rapid radio explosions.” It is believed that these phenomena – mysterious millisecond extragalactic radio explosions, are associated with pulsars and possibly young people, such as the Crab pulsar. “However,” says Enoto, “the relationship between the two is still controversial, and these findings, along with future discoveries about rapid radio explosions, will help us understand the relationship between these phenomena.”
He adds: “Our result not only has a wide impact on pulsar science and FRB, but is a fitting legacy for the 34 m Kashima telescope, which was a valuable tool for the radio astronomy community, but was irreparably affected by a typhoon in 2019. ”
The group also included scientists from the University of Tokyo, Hiroshima University, Changhua National University of Education, JAXA, NIST and GODMOTHER, and a number of other institutes around the world.
For more details on this discovery, read the strange X-ray overvoltages detected in Crab Pulsar’s radio explosions by NASA’s NICER.
Reference: “Enhanced X-ray Emission That Matches Giant Radio Pulses from the Crab Bracelet” by Teruaki Enoto, Toshio Terasawa, Shota Kisaka, Chin-Ping Hu, Sebastien Guillot, Natalia Lewandowska, Christian Malacaria, Paul S. Ray, Wynn CG Ho , Alice K. Harding, Takashi Okajima, Zaven Arzoumanian, Keith C. Gendreau, Zorawar Wadiasingh, Craig B. Markwardt, Yang Soong, Steve Kenyon, Slavko Bogdanov, Walid A. Majid, Tolga Güver, Gaurava K. Jaisawal, Rick Foster, Yasuhiro Murata, Hiroshi Takeuchi, Kazuhiro Takefuji, Mamoru Sekido, Yoshinori Yonekura, Hiroaki Misawa, Fuminori Tsuchiya, Takahiko Aoki, Munetoshi Tokumaru, Mareki Honma, Osamu Kameya, Tomoaki Oyama, Katsuaki Asanoata, Shinpei ,, Science.
DOI: 10.1126 / science.abd4659