This week, astronomers announce a newborn magnetar and a fast radio burst that’s bursting to a beat.
Around the time of the American Revolutionary War, a star exploded in the constellation Sagittarius, some 16,000 light-years away. The supernova left behind a burnt cinder, the just-discovered neutron star known as Swift J1818.0-1607.
Astronomers spotted this source of X-ray flashes on March 12, 2020, using NASA's Neil Gehrels Swift Observatory, an X-ray satellite. NuSTAR and the European Space Agency's XMM-Newton soon confirmed the discovery and helped astronomers understand what it was.
The collapsed stellar core squeezes two Suns' worth of mass into a sphere that could fit the length of Manhattan across it. Amazingly, that compact bulk spins around every 1.36 seconds. The object is ultramagnetized, with some 1,000 times the strength of a typical neutron star's magnetic field. This puts it into the class of magnetars, making it only the 31st member of this elusive class.
What's more, the magnetar is young. At only 240 years old, it's the youngest one known — a fledgling by astronomical standards. It could give astronomers a unique view on how such objects form. But first, the researchers will need additional measurements of the magnetar's spin; its almost-imperceptible slowdown is what enables astronomers to estimate its age.
Read more in NASA/JPL-Caltech's press release and in the preprint of the study, which Paolo Esposito (IUSS - School for Advanced Studies, Italy) and colleagues will publish in the Astrophysical Journal Letters.
Radio Bursts with a Beat
Fast radio bursts (FRBs) are brilliant, millisecond-long flashes of radio waves that mostly come from distant sources. What makes the flashes is still unknown.
The goal of the Canadian Hydrogen Intensity Mapping Experiment (CHIME) FRB Project is to amass as many of these sources as the radio array can find. The most active source in the CHIME catalog is designated FRB 180916.J0158+65. Back in January, astronomers announced they'd pinpointed its location in the outskirts of a nearby spiral galaxy.
Now, the CHIME/FRB collaboration has realized there's a rhythm to the 38 bursts recorded in the two years since the FRB's discovery.
Every 16 days, the source starts acting up, emitting roughly a burst every hour for a period of about five days. Then it's silent for the next 11 days or so before starting the cycle over again. The beat seems too long to be associated with the rotation of an object such as a neutron star. Instead, the researchers suggest, a stellar companion could be driving the beat.
This is the first FRB with a steady cadence to its bursts, but it could be that astronomers just haven't yet detected the beat of other FRBs.