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10 years of LOFAR highlights: Pulsar shows sudden mood swings

In 2013 an international research team – led by Dutch astronomers (SRON, NOVA and ASTRON) – discovers that pulsar PSR B0943+10 can both radically change the amounts of radio waves and X-ray waves it emits within seconds. Never before have scientists been able to determine whether a change in the amounts of emitted radio waves, a common phenomenon with pulsars, also influences the amount of X-ray waves that some pulsars emit.

Published by the editorial team, 3 June 2020

Thanks to LOFAR’s sensitivity, a team of scientists is able to closely monitor the amount of radio waves PSR B0943+10 emits. At the same time, X-ray space telescope XMM-Newton measures the amount of X-rays the pulsar emits.

A pulsar with glowing cones of radiation stemming from its magnetic poles – a state referred to as ‘radio-bright’ mode. (Credit: ESA/ATG medialab)

The scientists find that when PSR B0943+10 emits strong radio signals and clear pulses, the X-rays are weak. But when the radio emission switches to weak, the X-rays synchronously intensify. ‘To our surprise we found that when the brightness of the radio emission decreased to half the original brightness, the X-ray emission brightened by a factor of two!’ says project leader Wim Hermsen (SRON Netherlands Institute for Space Research/UvA). And only then the X-ray emission is pulsed. Lucien Kuiper (SRON), who scrutinised the data from XMM-Newton, concluded that this strongly suggests that a temporary ‘hotspot’ close to the pulsar’s magnetic pole switches on and off with the change of state.

A pulsar with glowing ‘hot-spots’ that are located at its magnetic poles, the likely sites of X-ray emission from old pulsars. In particular, the illustration shows the pulsar in a state characterised by bright X-ray emission, arising from the polar caps, and relatively low radio emission from the cones that stem from the pulsar’s magnetic poles (‘X-ray-bright/radio-quiet’ mode). (Credit: ESA/ATG medialab)

Most striking is that this ‘mood swing’ takes place within seconds, after which the pulsar remains stable in its new state for a few hours. The researchers publish their results in the scientific journal Science.

On 12 June 2020, LOFAR celebrates its tenth anniversary. The radio telescope is the world’s largest low frequency instrument and is one of the pathfinders of the Square Kilometre Array (SKA), which is currently being developed. Throughout its ten years of operation, LOFAR has made some amazing discoveries. It has been a key part of groundbreaking research, both in astronomy and engineering. Here we feature some – but definitely not all – of these past highlights, with surely more to come in the future.



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