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The magnetar produced by the neutron star merger has the brightest nova ever observed



The magnetar produced by the neutron star merger has the brightest nova ever observed

This image shows the light emitted by a thousand-beam nova produced by the merger of two neutron stars. The highest nova has a peak brightness of 10,000 times that of a kV nova, which is displayed as a bright spot (indicated by an arrow) on the upper left of the host galaxy. It is believed that the merger of neutron stars produced a magnetic pole with a very powerful magnetic field. The energy produced by that magnet brightened the material ejected from the explosion. Image source: NASA, ESA, W. Fong (Northwest University) and T. Laskar (University of Bath, UK)

Long ago, in the entire universe, huge gamma-ray bursts released more energy in half a second than the energy produced by the sun in the entire 10 billion years of life.


After the astrophysics team led by Northwestern University studied the incredibly bright explosions produced by light, X-rays, near-infrared and radio waves, they thought it might have discovered the birth of a magnetar.

Researchers believe that the magnetar was formed by the merger of two neutron stars, which is unprecedented. The merger produced a brilliant millennial nova, the brightest ever, and its light finally reached Earth on May 22, 2020. Light is first a gamma-ray explosion, called a short gamma-ray explosion.

Wenhui Wen of Northwestern University said: “When two neutron stars merge, the most common prediction is that they form a heavy neutron star, which will collapse into a black hole in a few milliseconds or less.” “Our research shows that For this particular short gamma-ray burst, the heavy object may have survived. Instead of collapsing into a black hole, it has become a magnetar: a rapidly rotating neutron star with a large magnetic field, dumping energy into the surrounding Environment and create the very bright light we see.”

The research has been Astrophysical Journal It will be released online later this year.

Mr. Fang is an assistant professor of physics and astronomy at Northwestern University’s Weinberg School of Arts and Sciences, and a member of CIERA (Center for Interdisciplinary Exploration and Research in Astrophysics). The research involved two undergraduates, three graduate students and three postdoctoral researchers in Fang’s laboratory.

“A new phenomenon is happening”

After NASA’s Neal Gellers Swift Observatory discovered light for the first time, scientists quickly recruited other telescopes, including NASA’s Hubble Space Telescope, the Very Large Array, WM Keck Observatory, and Las Cumbres Observatory’s global telescope network, To study the consequences of the explosion and its consequences. Host galaxy.

Fang’s team quickly realized that things did not add up.

Compared with X-ray and radio observations, the near-infrared emission detected by Hubble is too bright. In fact, it is 10 times brighter than expected.

Tanmoy Laskar of the University of Bath, a co-investigator of the study, said: “As data enters, we are forming a picture of the mechanism that produces the light we see.” “When we get the Hubble observation data, we must Completely change our thinking process, because the information added by Hubble makes us realize that we must abandon traditional thinking and new phenomena are happening. Then we must figure out what is the physical meaning behind these extremely high energy explosions.”

Magnetic monster

Fang and her team discussed several possibilities to explain the unusual brightness (called short gamma-ray bursts) seen by Hubble. Researchers believe that the short burst was formed by the merger of two neutron stars. These two neutron stars are extremely dense masses around the sun that are compressed into large cities like Chicago. Although most short-term gamma-ray bursts may cause black holes, the two neutron stars merged in this case may have joined together to form a magnetar with a very strong magnetic field, that is, a supermassive neutron star.

The magnetar produced by the neutron star merger has the brightest nova ever observed

This figure shows the process of forming a magnetodynamic kilovolt nova with a peak brightness of 10,000 times that of a classic nova. 1) Two orbiting neutron stars are spiraling closer and closer together. 2) They collide and merge, trigger an explosion, and release more energy in half a second than the energy produced by the sun in its entire lifetime of 10 billion years. 3) The merger formed a larger neutron star called a magnetar, which has an unusually strong magnetic field. 4) The magnetar deposits energy into the ejected material, causing it to emit light unexpectedly at infrared wavelengths. Image source: NASA, ESA and D. Player (STScI)

Laskar explained: “Basically, these magnetic field lines fixed on the star rotate at a speed of about 1,000 times per second, which creates a magnetized wind.” “These spin field lines extract the rotation of the neutron star formed during the merger. Energy and deposit that energy from the explosion into the ejector to make the matter glow brighter.”

Fang said: “We know that magnetars exist because we have seen them in the Milky Way.” “We think that most of them are formed by the explosive death of massive stars, which makes these highly magnetized neutron stars lag behind. However, There may be a small part of the neutron star merger. Under infrared light, this discovery becomes special.”

Unusually bright kaleidoscope

Kilonovae, which is usually 1,000 times brighter than classic novae, is accompanied by short bursts of gamma rays. The unique feature of the merging of two compact objects is that the radioactive decay of the heavy elements expelled during the merging process produces luminescence of daughter novae and coveted elements such as gold and uranium.

The paper’s co-author, Jillian Rastinejad, a graduate student in Fang’s laboratory, said: “So far, we have only one confirmed and well-sampled kaleidoscopic.” Therefore, finding that looks so different The new potential star of is particularly exciting. This discovery provides us with an opportunity to explore the diversity of new stars and their legacy. “

If the unexpected brightness seen by the Hubble telescope comes from magnets that deposit energy into kilovolt nuclear matter, then within a few short years, the matter ejected from the explosion will produce light in radio wavelengths. Subsequent radio observations may eventually prove that this is a magnetar, which can explain the origin of these objects.

Lasting Judd said: “Now, we have a very bright candidate new star, I am happy that the short gamma-ray burst and the neutron star merger bring us new surprises.”


Afterglow reveals the nature and origin of neutron star collision


More information:
“The broadband counterpart of the short GRB 2005221 with z = 0.5536: a glowing kilovolt nova or a quasi-DC output with reverse impact?” arXiv: 2008.08593 [astro-ph.HE] arxiv.org/abs/2008.08593

Provided by Northwest University

Citation: The result of neutron star merger produced the brightest nova magnetar ever observed (November 12, 2020) from https://phys.org/news/2020-11-neutron-star-merger-results- magnetar.html retrieved until November 12, 2020

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