A nearby flaring magnetar
Shortly after the initial detection of a possible FRB-like flare from a nearby magnetar last week, researchers sent two telegrams via
The Astronomer’s Telegram (ATel), a web-based bulletin board where astronomers can post about pressing observations. The ATels outlined that a bright radio burst was spotted in the direction of a magnetar in our Milky Way called SGR 1935+2154, located in the constellation Vulpecula. It’s important to note, however, that ATels are not published papers. They instead serve as a way for astronomers to announce time-critical discoveries to the larger astronomical community.
Both of the telescopes involved in the initial detection — the Canadian Hydrogen Intensity Mapping Experiment (CHIME) and the Survey for Transient Astronomical Radio Emission 2 (STARE2) in California — are designed to monitor large areas of the sky for FRBs or FRB-like radio signals. The first radio burst, which lasted just 30 milliseconds, had several FRB-like properties. It was also the very first time this magnetar had ever been detected in radio frequencies.
There was one key difference between this flare and more distant FRBs, though. If this burst happened at the distance of the closest-known FRB beyond the Milky Way, it would be about 1/1,000 as bright. (X-ray telescopes also reported via ATels the detection of a “burst forest” of radiation at the same time as the radio burst, albeit about a hundred times weaker than a typical giant flare from a magnetar.) A few days later, the Five-hundred-meter Aperture Spherical radio Telescope (FAST) in China detected another burst from the magnetar, which indicates it’s entering an active radio phase.
Although much fainter than distant FRBs, spotting nearby bursts with FRB-like properties is a startling discovery for astronomers who have long wondered whether fainter versions of FRBs exist close to Earth, even if they rarely flare. “We can imagine FRB intensities occur on a range of luminosities, and we are only detecting the brightest ones now,” says Shri Kulkarni, an astronomer at the Caltech and project investigator for STARE2. This assumption, combined with their data, led the STARE2 group to go as far as stating in their bulletin that “we conclude active magnetars are a source of FRBs at extragalactic distances.”
The CHIME radio telescope team has not yet drawn such a strong conclusion, but they are nonetheless also excited about the new nearby burst. “It’s certainly not as bright as the FRBs coming from far away,” says Paul Scholz, an astronomer at the University of Toronto and lead author of the CHIME bulletin. “But it’s definitely a tempting connection to make.”