NICER / ISS Science Nugget
for April 15, 2021
Unlocking a secret of the Crab Pulsar with NICER/ISS and ground-based telescopes
The Crab Nebula is a remnant of a supernova explosion in 1054 in the constellation Taurus and the famous first object in the Messier catalog (M1). The Crab Pulsar is located at the center of this remnant and observed in almost all wavelengths, from radio waves to visible light, X-rays, and gamma rays. The Crab Pulsar is one of the most well-studied objects in astronomy, and it is a fascinating object that can yield new insights when observed with the most advanced instruments.
Since the discovery of the Crab Pulsar, it is known that this pulsar sporadically produces a bright burst of radiation called "giant pulses", which are 100 to 1000 times stronger than the regular radio pulses. For a long time, giant pulses were thought to be a phenomenon only with radio waves. However, in 2003, a few percent enhancement of visible light was discovered to occur at the same time as giant pulses. Astronomers were surprised by this unexpected discovery.
After the finding in the optical band, astronomers had been attempting to search for a similar enhancement in the higher energy bands, X-rays and gamma rays, using different types of observatories. However none of them succeeded in detection.
After NICER began operating in 2017, the NICER team coordinated an observational campaign of the Crab Pulsar with two radio telescopes in Japan. After two years of data accumulation, the NICER team succeeded in detecting a ∼4% X-ray enhancement associated with giant pulses. Because the X-ray flux of the Crab Pulsar is higher than that at low-energies, the energy released by giant pulses is 10-100 times larger than previously thought, even though the X-ray amplification is small.
This discovery helps astronomers better understand the mechanism of electromagnetic radiation from pulsars and models of mysterious fast radio bursts in the distant Universe.
This result was published in Science
(Enoto, Terasawa, Kisaka, Chin-ping et al., Science 2021) and featured in a NASA press release
Figure: A four-frame manga depicting important results of this research personified by cute characters. (Credit: higgstan.com)