24/04/2024
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Whereas ESA’s Integral was observing the sky, it abruptly noticed a burst of gamma-rays coming from the close by galaxy M82. Just a few hours later, ESA’s XMM-Newton looked for an afterglow from the explosion however discovered none. Astronomers realised that the burst should have been an extra-galactic flare from a magnetar, a younger neutron star with an exceptionally sturdy magnetic subject.
A curious sign from a close-by galaxy
In November 2023 ESA’s Integral noticed a sudden explosion from a uncommon object. For less than a tenth of a second, a brief burst of energetic gamma-rays appeared from the course of the intense galaxy M82.
The satellite tv for pc information have been acquired within the Integral Science Data Centre in Geneva, from the place a gamma-ray burst alert was despatched out to astronomers worldwide, solely 13 seconds after its detection. The IBAS (Integral Burst Alert System) software program gave an computerized localisation coinciding with the close by galaxy M82.
Now it was as much as astronomers to determine what had occurred; was this one of many extra widespread gamma-ray bursts or a uncommon event of a large flare from a magnetar?
“We instantly realised that this was a particular alert. Gamma-ray bursts come from far-away and wherever within the sky, however this burst got here from a brilliant close by galaxy,” explains Sandro Mereghetti of the Nationwide Institute for Astrophysics (INAF–IASF) in Milan, Italy, and lead creator of a paper on this discovery.
The workforce requested ESA’s XMM-Newton area telescope to carry out a follow-up commentary of the burst’s location as quickly as attainable. If this had been a brief gamma-ray burst, attributable to two colliding neutron stars, the collision would have created gravitational waves and have an afterglow in X-rays and visual gentle.
“XMM-Newton’s observations solely confirmed the new gasoline and stars within the galaxy. If this explosion had been a brief gamma-ray burst, we’d have seen a fading supply of X-rays coming from its location, however this afterglow was not current,” provides co-author Michela Rigoselli from INAF.
“Utilizing ground-based optical telescopes, together with the Italian Telescopio Nazionale Galileo and the French Observatoire de Haute-Provence, we appeared for a sign in seen gentle, beginning only some hours after the explosion, however once more we didn’t discover something. With no sign in X-rays and visual gentle, and no gravitational waves measured by detectors on Earth (LIGO/VIRGO/KAGRA), we’re sure the sign got here from a magnetar,” concludes Sandro.
Jan-Uwe Ness, ESA’s Integral Undertaking Scientist explains: “When sudden observations like this are picked up, Integral and XMM-Newton will be versatile of their schedules, which is crucial in time-crucial discoveries. On this case, if the observations had been carried out even only a day later, we’d not have such sturdy proof that this was certainly a magnetar and never a gamma-ray burst.”
Magnetars: mega-magnetic, just lately lifeless
When stars extra huge than eight instances the Solar die, they explode in a supernova that leaves a black gap or neutron star behind. Neutron stars are very compact stellar remnants with greater than the mass of the Solar packed right into a sphere with the dimensions of a metropolis. They rotate shortly and have sturdy magnetic fields.
“Some younger neutron stars have further sturdy magnetic fields, greater than 10 000 instances that of typical neutron stars. These are known as magnetars. They emit power away in flares, and sometimes these flares are gigantic,” clarifies Ashley Chrimes, Analysis Fellow at ESA.
Nonetheless, prior to now 50 years of gamma-ray observations, solely three large flares have been seen from magnetars in our galaxy. These outbursts are very sturdy: one which was detected in December 2004, got here from 30 000 light-years from us however was nonetheless highly effective sufficient to have an effect on the higher layers of Earth’s ambiance. Just like how Photo voltaic flares, coming from a lot nearer to us, affect it.
“The flare detected by Integral is the primary affirmation of a magnetar outdoors of the Milky Approach. We suspect that a number of the different ‘quick gamma-ray bursts’ Integral and different satellites have revealed are additionally large flares from magnetars,” continues Sandro.
“This discovery opens our seek for different extra-galactic magnetars. If we are able to discover many extra, we are able to begin to perceive how typically these flares occur and the way these stars lose power within the course of,” provides Ashley.
“Nonetheless, outbursts of such quick length can solely be captured serendipitously when an observatory is already pointing in the correct course. This makes Integral with its massive subject of view, greater than 3000 instances higher than the sky space lined by the Moon, so vital for these detections,” emphasises Jan-Uwe.
M82 is a brilliant galaxy the place star-formation takes place. In these areas huge stars are born, reside quick turbulent lives and depart behind a neutron star. The invention of a magnetar on this area confirms that magnetars are doubtless younger neutron stars. The seek for extra magnetars will proceed in different star-forming areas, to perceive these extraordinary astronomical objects.
