In 2014, NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) and the agency’s Swift satellite observed an X-flare from the supermassive black hole in Markarian 335, a galaxy located 324 million light-years away in the constellation Pegasus. The observations allowed astronomers to link a shifting corona to an X-ray flare for the first time.
A supermassive black hole is depicted in this artist’s concept, surrounded by a swirling disk of material falling onto it. Image credit: NASA / JPL-Caltech.
According to the astronomers, led by Dr Dan Wilkins of Saint Mary’s University in Canada, supermassive black holes send out beams of X-rays when their surrounding coronas shoot, or launch, away from the black holes.
“This is the first time we have been able to link the launching of the corona to a flare,” said Dr Wilkins, who is the lead author of a new study on the findings accepted for publication in the Monthly Notices of the Royal Astronomical Society (arXiv.org preprint).
“Coronas are made up of highly energetic particles that generate X-ray light, but details about their appearance, and how they form, are unclear.”
Dr Wilkins and his colleagues have been using NASA’s Swift space telescope to regularly monitor Markarian 335 since 2007.
On 29 August 2014, the telescope caught a huge flare coming from the supermassive black hole in this galaxy. Eight days later, NASA’s NuSTAR set its X-ray eyes on the target, witnessing the final half of the flare event.
After careful scrutiny of the data, the scientists realized they were seeing the ejection and eventual collapse of the black hole’s corona.
“The corona gathered inward at first and then launched upwards like a jet,” Dr Wilkins explained.
“We still don’t know how jets in black holes form, but it’s an exciting possibility that this black hole’s corona was beginning to form the base of a jet before it collapsed.”
The corona gives off X-ray light that has a slightly different spectrum than the light coming from the disk around the black hole.
By analyzing a spectrum of X-ray light across a range of wavelengths observed by both Swift and NuSTAR, the team could tell that the corona X-ray light had brightened, and that this brightening was due to the motion of the corona.
The corona associated with the supermassive black hole in Markarian 335 was traveling at about 20% the speed of light.
When this happens, and the corona launches in our direction, its light is brightened in an effect called relativistic Doppler boosting.
Putting this all together, the results show that the X-ray flare from this black hole was caused by the ejected corona.
“The nature of the energetic source of X-rays we call the corona is mysterious, but now with the ability to see dramatic changes like this we are getting clues about its size and structure,” said Dr Fiona Harrison of the California Institute of Technology in Pasadena, who was not involved in the study.
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D.R. Wilkins et al. 2015. Flaring from the supermassive black hole in Mrk 335 studied with Swift and NuSTAR. MNRAS, accepted for publication; arXiv: 1510.07656
