A global scientific collaboration using data from NASA’s Neutron star Interior Composition Explorer (NICER) telescope on the International Space Station has detected X-ray waves accompanying radio bursts from the pulsar of the Crab Nebula. The finding shows that these bursts, called giant radio impulses, release far more energy than previously suspected.
A pulsar is a type of rapidly rotating neutron star, the crushed city-sized nucleus of a star that exploded like a supernova. A young, isolated neutron star can rotate dozens of times every second, and its swirling magnetic field amplifies rays of radio waves, visible light, X-rays and gamma rays. If these rays sweep past Earth, astronomers observe unparalleled emission impulses and classify the object as a pulsar.
“Out of more than 2,800 cataloged pulsars, Crab Pulsar is one of only a few that emits giant radio pulses that occur sporadically and can be hundreds to thousands of times brighter than regular pulses,” said researcher Teruaki Enoto at the RIKEN Cluster for Pioneering research in Wako, Saitama Prefecture, Japan. “After decades of observations, only the crab has been shown to improve its giant radio impulses with emissions from other parts of the spectrum.”
The new study, which appears in the April 9 issue of Science and is now available online, analyzing the largest amount of simultaneous X-ray and radio data ever collected from a pulsar. It expands the observed energy range associated with this improvement phenomenon thousands of times.
Located about 6,500 light-years away in the constellation Taurus, the crab nebula and its pulsar formed in a supernova whose light reached Earth in July 1054. The neutron star spins 30 times every second, and at X-ray and radio wavelengths it is among the brightest pulses in the sky.
Between August 2017 and August 2019, Enoto and his colleagues used NICER to repeatedly observe Crab pulsars in X-rays with energies up to 10,000 electron volts or thousands of visible light. While NICER watched, the team also studied the object using at least one of two terrestrial radio telescopes in Japan – the 34-meter dish at the Kashima Space Technology Center and the 64-meter dish at the Japanese aviation agency Usuda Deep Space Center, both operating at a frequency at 2 gigahertz.
he combined datasets effectively giving researchers almost a day and a half of simultaneous X-ray and radio coverage. In all, they captured activity across 3.7 million pulse rotations and netted some 26,000 giant radio pulses.
Huge impulses erupt quickly and peak in millionths of a second and appear unpredictable. However, when they do occur, they coincide with the regular clockwork pulsations.
NICER registers the arrival time of each X-ray it registers within 100 nanoseconds, but the timing accuracy of the telescope is not the only advantage of this study.
“NICER’s capacity to observe bright X-ray sources is almost four times greater than the combined brightness of both the pulsar and its nebula,” said Zaven Arzoumanian, the project’s scientific director at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “So these observations were largely unaffected by pileup – where a detector counts two or more x-rays as a single event – and other problems that have complicated previous analyzes.”
Enoto’s team combined all X-ray data that coincided with giant radio pulses, which revealed an X-ray increase of approx. 4% that occurred in sync with them. It is remarkably similar to the 3% increase in visible light also associated with the phenomenon, discovered in 2003. Compared to the brightness difference between Krabb’s regular and gigantic impulses, these changes are remarkably small and present a challenge for theoretical models to explain.
The improvements suggest that gigantic impulses are a manifestation of underlying processes that produce emissions that span the electromagnetic spectrum, from radio to X-rays. And because X-rays pack millions of times the radio wave, even a modest increase represents a major energy contribution. The researchers conclude that the total emitted energy associated with a giant pulse is tens to hundreds of times higher than previously estimated from radio and optical data alone.
“We still do not understand how or where pulses produce their complex and far-reaching emission, and it is gratifying to have contributed yet another piece to the multi-wave puzzle in these fascinating objects,” Enoto said.
Huge impulses detected in the pulsar PSR J1047−6709
T. Enoto et al., “Improved X-ray emission coinciding with giant radio impulses from the crab tubercle,” Science (2021). science.sciencemag.org/cgi/doi… 1126 / science.abd4659
Provided by NASA’s Goddard Space Flight Center
Citation: Huge radio pulses from pulsars are hundreds of times more energetic than previously thought (2021, April 8) retrieved April 9, 2021 from https://phys.org/news/2021-04-giant-radio-pulses-pulsars-hundreds . html
This document is subject to copyright. Except for any fair trade for the purpose of private examination or research, no parts may be reproduced without written permission. The content is provided for informational purposes only.