And they could be extremely important, acting as the missing link between the smallest black holes in the cosmos and the largest, supermassive black holes such as the one at the centre of our own galaxy. LFBots could reveal the locations of intermediate mass black holes, and how common they are.
“The intermediate mass black hole model is the most exciting,” says Perley. “It is still kind of debated in the community whether intermediate mass black holes really exist. The evidence has been quire sparing.”
To find out for certain what LFBots are, we really need a much larger sample of them. “Unfortunately, they’re really rare,” says Perley. Data on around 100 of them would be an ideal next step, he adds. We might get a little closer to that number next year, when an Israeli orbital telescope called the Ultraviolet Transient Astronomy Satellite (Ultrasat) is set to launch. It is expected to find many more LFBots among other cosmic transients, thanks to its very large field of view of 204 square degrees, equivalent to seeing 1,000 full Moons.
Other space telescopes, such as the James Webb Space Telescope (JWST), could gather more data about singular LFBots so long as they could be trained in the direction of an explosion while it is brightening. “JWST would be perfect,” says Metzger. However, getting time on the telescope to do such observations has proved difficult. “I proposed this two times,” says Ho, but she had no luck. “I’ll try again this year.”
Until more data arrives, the mystery of these strange explosions will linger. What is clear is that LFBots have proved far more unusual than anyone expected.
“I thought this was going to be a fun, one-off project,” says Perley. “But it turned out to really be this completely separate type of phenomenon. They have become more and more interesting.”