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天文学家从宇宙最强磁铁之一发现奇异且前所未有的活动

天文学家从宇宙最强磁铁之一发现奇异且前所未有的活动

太空探索 天文学 双语译文
191
2021-02-04 18:41:20

Astronomers spot bizarre, never-before-seen activity from one of the strongest magnets in the universe

天文学家从宇宙中最强的磁铁之一发现奇异的,前所未有的活动

by ARC Centre of Excellence for Gravitational Wave Discovery

ARC引力波发现卓越中心

艺术家对主动式磁星雨燕J1818.0-1607的印象.png


Artist’s impression of the active magnetar Swift J1818.0-1607. Credit: Carl Knox, OzGrav.

艺术家对主动式磁星雨燕J1818.0-1607的印象。图片来源:卡尔·诺克斯(OlGrav)。


Astronomers from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) and CSIRO have just observed bizarre, never-seen-before behavior from a radio-loud magnetar—a rare type of neutron star and one of the strongest magnets in the universe.

来自ARC引力波发现卓越中心(OzGrav)和CSIRO的天文学家刚刚观察到了无线电波电磁波的一种奇怪的,从未见过的行为,这是一种罕见的中子星,也是宇宙中最强的磁体之一。


Their new findings, published today in the Monthly Notices of the Royal Astronomical Society (MNRAS), suggest magnetars have more complex magnetic fields than previously thought, which may challenge theories of how they are born and evolve over time.

他们的新发现发表在今天的《皇家天文学会月刊》(MNRAS)上,表明磁星具有比以前认为的更复杂的磁场,这可能会挑战它们的诞生和演化理论。


Magnetars are a rare type of rotating neutron star with some of the most powerful magnetic fields in the universe. Astronomers have detected only 30 of these objects in and around the Milky Way—most of them detected by X-ray telescopes following a high-energy outburst.

磁场是一种罕见的旋转中子星,具有宇宙中某些最强大的磁场。天文学家仅在银河系及其周围发现了30个这些物体,其中大部分在高能量爆发后被X射线望远镜探测到。


However, a handful of these magnetars have also been seen to emit radio pulses similar to pulsars—the less-magnetic cousins of magnetars that produce beams of radio waves from their magnetic poles. Tracking how the pulses from these radio- loud magnetars change over time offers a unique window into their evolution and geometry.

但是,还可以看到,这些磁星中的少数几个会发出类似于脉冲星的无线电脉冲,后者是磁星的磁性较弱的近亲,它们从其磁极产生无线电波。跟踪这些无线电磁铁的脉冲如何随时间变化,为了解其演化和几何形状提供了独特的窗口。


In March 2020, a new magnetar named Swift J1818.0-1607 (J1818 for short) was discovered after it emitted a bright X-ray burst. Rapid follow-up observations

20203月,在发射出明亮的X射线爆发后,发现了一种名为Swift J1818.0-1607(简称J1818)的新型磁星。快速随访观察


detected radio pulses originating from the magnetar. Curiously, the appearance of the radio pulses from J1818 were quite different from those detected from other radio-loud magnetars.

探测到来自电磁体的无线电脉冲。奇怪的是,来自J1818的无线电脉冲的出现与从其他无线电扬声器的电磁波中检测到的完全不同。


Most radio pulses from magnetars maintain a consistent brightness across a wide range of observing frequencies. However, the pulses from J1818 were much brighter at low frequencies than high frequencies—similar to what is seen in pulsars, another more common type of radio-emitting neutron star.

磁石的大多数无线电脉冲在很宽的观测频率范围内都能保持一致的亮度。但是,来自J1818的脉冲在低频比高频要亮得多,这与脉冲星(另一种更常见的发射中子星的脉冲星)相似。


In order to better understand how J1818 would evolve over time, a team led by scientists from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) observed it eight times using the CSIRO Parkes radio telescope (also known as Murriyang) between May and October 2020.

In order to better understand how J1818 would evolve over time, a team led by scientists from the ARC Centre of Excellence for Gravitational Wave Discovery (OzGrav) observed it eight times using the CSIRO Parkes radio telescope (also known as Murriyang) between May and October 2020.


During this time, they found the magnetar underwent a brief identity crisis: In May it was still emitting the unusual pulsar-like pulses that had been detected previously; however, by June, it had started flickering between a bright and a weak state. This flickering behavior reached a peak in July, when the astronomers saw it flickering back and forth between pulsar-like and magnetar-like radio pulses.

在此期间,他们发现磁石经历了短暂的身份危机:5月份,它仍在散发以前检测到的异常脉冲状脉冲;但是,到了6月,它开始在明亮和脆弱状态之间闪烁。这种闪烁现象在7月份达到了顶峰,当时天文学家看到它在脉冲状和电磁状无线电脉冲之间来回闪烁。


"This bizarre behavior has never been seen before in any other radio-loud magnetar," explains study lead author and Swinburne University/CSIRO Ph.D. student Marcus Lower. "It appears to have only been a short-lived phenomenon, as by our next observation, it had settled permanently into this new magnetar-like state."

研究的主要作者和斯威本大学/ CSIRO博士解释说:这种奇怪的行为以前从未在任何其他的无线电磁石中见过。学生Marcus Lower这似乎只是一个短暂的现象,因为根据我们的下一个观察,它已经永久性地陷入了这种新的类似电磁体的状态。


The scientists also looked for pulse shape and brightness changes at different radio frequencies and compared their observations to a 50-year-old theoretical model. This model predicts the expected geometry of a pulsar, based on the twisting direction of its polarized light.

科学家还寻找了不同无线电频率下的脉冲形状和亮度变化,并将其观察结果与已有50年历史的理论模型进行了比较。该模型基于脉冲光的偏振方向来预测脉冲星的预期几何形状。


"From our observations, we found that the magnetic axis of J1818 isn't aligned with its rotation axis," says Lower. "Instead, the radio-emitting magnetic pole appears to be in its southern hemisphere, located just below the equator. Most other magnetars have magnetic fields that are aligned with their spin axes or are a little ambiguous. This is the first time we have definitively seen a magnetar with a misaligned magnetic pole."

从我们的观察中,我们发现J1818的磁轴与它的旋转轴不对齐,” Lower说。 相反,发射电磁波的磁极似乎位于赤道正下方的南半球。大多数其他的磁星具有与自旋轴对齐或有点模糊的磁场。这是我们第一次明确地看到磁极未对准的磁星。


Remarkably, this magnetic geometry appears to be stable over most observations. This suggests any changes in the pulse profile are simply due to variations in the height the radio pulses are emitted above the neutron star surface. However, the August 1st 2020 observation stands out as a curious exception.

值得注意的是,这种磁性几何形状在大多数观察结果中似乎都是稳定的。这表明脉冲轮廓的任何变化仅是由于无线电脉冲在中子星表面上方发射的高度的变化引起的。然而,202081日的观察结果是一个奇怪的例外。


"Our best geometric model for this date suggests that the radio beam briefly flipped over to a completely different magnetic pole located in the northern hemisphere of the magnetar," says Lower.

目前为止,我们最好的几何模型表明,无线电束短暂地翻转到了位于磁层北半球的完全不同的磁极,” Lower说。


A distinct lack of any changes in the magnetar's pulse profile shape indicate the same magnetic field lines that trigger the 'normal' radio pulses must also be responsible for the pulses seen from the other magnetic pole.

磁星的脉冲轮廓形状明显没有任何变化,表明触发正常无线电脉冲的相同磁场线也必须负责从另一个磁极看到的脉冲。


The study suggests this is evidence that the radio pulses from J1818 originate from loops of magnetic field lines connecting two closely spaced poles, like those seen connecting the two poles of a horseshoe magnet or sunspots on the sun. This is unlike most ordinary neutron stars, which are expected to have north and south poles on opposite sides of the star that are connected by a donut-shaped magnetic field.

研究表明,有证据表明,来自J1818的无线电脉冲来自连接两个紧密间隔的磁极的磁力线回路,就像看到的连接马蹄形磁铁或太阳黑子的两个极一样。这与大多数普通中子星不同,大多数中子星预期在恒星相对两侧具有南极和北极,它们通过一个甜甜圈形磁场连接。


This peculiar magnetic field configuration is also supported by an independent study of the X-rays pulses from J1818 that were detected by the NICER telescope on board the International Space Station. The X-rays appear to come from either a single distorted region of magnetic field lines that emerge from the magnetar surface or two smaller, but closely spaced, regions.

通过对国际空间站上的NICER望远镜检测到的来自J1818X射线脉冲的独立研究,也支持了这种特殊的磁场配置。 X射线似乎来自磁场线的单个变形区域,该区域是从磁层表面发出的,或者是两个较小但间隔很小的区域。


These discoveries have potential implications for computer simulations of how magnetars are born and evolve over long periods of time, as more complex magnetic field geometries will change how quickly their magnetic fields are expected to decay over time. Additionally, theories that suggest fast radio bursts can originate from magnetars will have to account for radio pulses potentially originating from multiple active sites within their magnetic fields.

这些发现对于计算机模拟磁星如何在很长一段时间内诞生和演化具有潜在的影响,因为更复杂的磁场几何形状将改变其磁场随时间衰减的速度。此外,暗示快速无线电脉冲可以源自磁星的理论将不得不考虑可能源自其磁场内多个活动位置的无线电脉冲。


Catching a flip between magnetic poles in action could also afford the first opportunity to map the magnetic field of a magnetar.

在动作中的磁极之间捕捉翻转也可以为映射磁星的磁场提供第一个机会。


"The Parkes telescope will be watching the magnetar closely over the next year" says scientist and study co-author Simon Johnston, from the CSIRO Astronomy and Space Science.

科学家和研究合著者,CSIRO天文学与太空科学学院的西蒙·约翰斯顿说:明年帕克斯望远镜将密切关注磁层。


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 来源于:phys

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