A surprisingly vibrant cosmic blast may need marked the beginning of a magnetar. If that’s the case, it will be the primary time that astronomers have witnessed the formation of this type of quickly spinning, extraordinarily magnetized stellar corpse.
That dazzling flash of light was made when two neutron stars collided and merged into one large object, astronomers report in an upcoming concern of the Astrophysical Journal. Although the particularly vibrant mild may imply {that a} magnetar was produced, different explanations are attainable, the researchers say.
Astrophysicist Wen-fai Fong of Northwestern College in Evanston, Sick., and colleagues first noticed the positioning of the neutron star crash as a burst of gamma-ray mild detected with NASA’s orbiting Neil Gehrels Swift Observatory on Might 22. Comply with-up observations in X-ray, seen and infrared wavelengths of sunshine confirmed that the gamma rays have been accompanied by a attribute glow referred to as a kilonova.
Kilonovas are thought to type after two neutron stars, the ultradense cores of lifeless stars, collide and merge. The merger sprays neutron-rich materials “not seen anyplace else within the universe” across the collision website, Fong says. That materials quickly produces unstable heavy elements, and people parts quickly decay, heating the neutron cloud and making it glow in optical and infrared mild (SN: 10/23/19).
A brand new research finds that two neutron stars collided and merged, producing an particularly vibrant flash of sunshine and probably making a form of quickly spinning, extraordinarily magnetized stellar corpse referred to as a magnetar (proven on this animation).
Astronomers assume that kilonovas type each time a pair of neutron stars merge. However mergers produce different, brighter mild as nicely, which may swamp the kilonova sign. In consequence, astronomers have seen only one definitive kilonova before, in August 2017, although there are different potential candidates (SN: 10/16/17).
The glow that Fong’s staff noticed, nevertheless, put the 2017 kilonova to disgrace. “It’s doubtlessly essentially the most luminous kilonova that we’ve ever seen,” she says. “It principally breaks our understanding of the luminosities and brightnesses that kilonovae are presupposed to have.”
The largest distinction in brightness was in infrared mild, measured by the Hubble House Telescope about 3 and 16 days after the gamma-ray burst. That mild was 10 instances as vibrant as infrared mild seen in earlier neutron star mergers.
“That was the actual eye-opening second, and that’s once we scrambled to seek out an evidence,” Fong says. “We needed to give you an additional supply [of energy] that was boosting that kilonova.”
Her favourite clarification is that the crash produced a magnetar, which is a kind of neutron star. Usually, when neutron stars merge, the mega-neutron star that they produce is just too heavy to outlive. Virtually instantly, the star succumbs to intense gravitational forces and produces a black gap.
But when the supermassive neutron star is spinning quickly and is very magnetically charged (in different phrases, is a magnetar), it may save itself from collapsing. Each the help of its personal rotation and dumping power, and thus some mass, into the encompassing neutron-rich cloud may hold the star from turning right into a black gap, the researchers recommend. That further power in flip would make the cloud give off extra mild — the additional infrared glow that Hubble noticed.
However there are different attainable explanations for the additional vibrant mild, Fong says. If the colliding neutron stars produced a black gap, that black gap may have launched a jet of charged plasma transferring at practically the velocity of sunshine (SN: 2/22/19). The small print of how the jet interacts with the neutron-rich materials surrounding the collision website may additionally clarify the additional kilonova glow, she says.
If a magnetar was produced, “that might inform us one thing in regards to the stability of neutron stars and the way large they will get,” Fong says. “We don’t know the utmost mass of neutron stars, however we do know that most often they’d collapse right into a black gap [after a merger]. If a neutron star did survive, it tells us about beneath what situations a neutron star can exist.”
Discovering a child magnetar can be thrilling, says astrophysicist Om Sharan Salafia of Italy’s Nationwide Institute for Astrophysics in Merate, who was not concerned within the new analysis. “A new child extremely magnetized, extremely rotating neutron star that kinds from the merger of two neutron stars has by no means been noticed earlier than,” he says.
However he agrees that it’s too quickly to rule out different explanations. What’s extra, current pc simulations recommend that it is perhaps troublesome to see a new child magnetar even when it fashioned, he says. “I wouldn’t say that is settled.”
Observing how the item’s mild behaves over the subsequent 4 months to 6 years, Fong and her colleagues have calculated, will show whether or not or not a magnetar was born.
Fong herself plans to maintain following up on the mysterious object with present and future observatories for a very long time. “I’ll be monitoring this until I’m previous and gray, in all probability,” she says. “I’ll prepare my college students to do it, and their college students.”