A Source of Mysterious Repeating Radio Signals From Space Has Been Identified
A Source of Mysterious Repeating Radio Signals From Space Has Been Identified
太空神秘重复无线电信号的来源已被确认
There is a mysterious phenomenon in which strong radio signals arrive periodically from space, yet their source remains completely unknown. Known as “long-period radio transients” (LPTs), these phenomena are observed as radio bursts that repeat at intervals ranging from several minutes to several hours. Only a dozen or so examples have been discovered within the Milky Way, and their physical nature has long remained a mystery.
太空中有这样一种神秘现象：强烈的无线电信号周期性地从太空中传来，但其来源却完全未知。这些现象被称为“长周期无线电瞬变”（LPTs），表现为以几分钟到几小时不等的时间间隔重复出现的无线电脉冲。在银河系内仅发现了十几个此类案例，其物理本质长期以来一直是个谜。
Previous research has suggested that candidates for the source of LPTs include neutron stars known as magnetars, which rotate extremely slowly, and binary systems consisting of white dwarfs with companion stars. However, the magnetar hypothesis faces the problem of contradicting existing theoretical models.
此前的研究认为，LPTs 的潜在来源包括旋转极其缓慢的磁星（中子星的一种），以及由白矮星和伴星组成的双星系统。然而，磁星假说面临着与现有理论模型相矛盾的问题。
On the other hand, while a few cases suggesting a connection to white dwarf binaries have been reported, there had been no cases in which the accretion process was directly confirmed to be actually occurring.
另一方面，虽然此前已有少数案例暗示其与白矮星双星系统有关，但一直没有案例能直接证实吸积过程确实正在发生。
Against this backdrop, an international research team led by the University of Sydney in Australia conducted a sky-survey using the Australian Square Kilometer Array Pathfinder (ASKAP) radio telescope and identified the true nature of a mysterious object named ASKAP J174508.9-505149. These observational results are said to be the strongest evidence to date pointing to LPT as one of the sources of this phenomenon.
在此背景下，由澳大利亚悉尼大学领导的一个国际研究团队利用澳大利亚平方公里阵列探路者（ASKAP）射电望远镜进行了巡天观测，并确定了一个名为 ASKAP J174508.9-505149 的神秘天体的真实本质。据称，这些观测结果是迄今为止最有力的证据，表明 LPT 是该现象的来源之一。
“For the first time we have pinpointed the origin of these signals,” said Kovi Rose, a doctoral student at the University of Sydney’s School of Physics and the Commonwealth Scientific and Industrial Research Organization, in a press release. “We’ve been able to show that the source for one of these transients comes from a white dwarf actively pulling material from a companion star.”
“我们首次锁定了这些信号的来源，”悉尼大学物理学院及澳大利亚联邦科学与工业研究组织（CSIRO）的博士生 Kovi Rose 在新闻发布会上表示，“我们已经能够证明，其中一个瞬变源来自一颗正在积极从伴星吸取物质的白矮星。”
A White Dwarf and a Companion Star
白矮星与伴星
Rose and his research team confirmed through spectroscopic observations that ASKAP J1745-5051 exhibits hydrogen emission lines (the Balmer series) and helium emission lines (HeI and HeII). In particular, the strong HeII emission line is known as an optical feature characteristic of “magnetic cataclysmic variables.”
Rose 和他的研究团队通过光谱观测证实，ASKAP J1745-5051 表现出氢发射线（巴尔末系）和氦发射线（HeI 和 HeII）。特别是强烈的 HeII 发射线，被认为是“磁激变变星”的光学特征。
Cataclysmic variables is a general term for close binary systems in which a white dwarf accretes matter from a companion star. Among these, those in which the white dwarf possesses a strong magnetic field and gas accretes along magnetic field lines are called “magnetic cataclysmic variables.”
激变变星是对紧密双星系统的统称，其中白矮星会从伴星吸积物质。在这些系统中，如果白矮星拥有强磁场，且气体沿磁力线吸积，则被称为“磁激变变星”。
Furthermore, analysis of the radial velocities of the Balmer series emission lines revealed that the orbital period of this binary system is approximately 1.368 hours, which was confirmed to match the repetition period of the radio pulses, approximately 1.345 hours. Furthermore, based on the orbital period, the companion star’s mass was estimated to be approximately 0.096 times that of the sun, and its radius approximately 0.13 times that of the sun, indicating that it corresponds to an M6-class red dwarf.
此外，对巴尔末系发射线径向速度的分析显示，该双星系统的轨道周期约为 1.368 小时，经证实与无线电脉冲的重复周期（约 1.345 小时）相吻合。此外，根据轨道周期推算，伴星的质量约为太阳的 0.096 倍，半径约为太阳的 0.13 倍，表明它是一颗 M6 型红矮星。
In other words, ASKAP J1745-5051 is a binary system in which a white dwarf and a red dwarf orbit each other at an extremely close distance. A white dwarf is the high-density remnant of a star that has reached the end of its life; although it is about the size of Earth, its mass is comparable to that of the sun. Its companion, the red dwarf, is larger but less dense, with a mass of only about one-tenth that of the Sun. The two stars orbit each other in a short period of just over one hour.
换句话说，ASKAP J1745-5051 是一个由白矮星和红矮星在极近距离内相互绕转的双星系统。白矮星是恒星生命终结后的高密度残骸；虽然它的大小与地球相当，但其质量却与太阳相当。它的伴星——红矮星体积更大但密度较低，质量仅为太阳的十分之一左右。这两颗恒星以仅一个多小时的短周期相互绕转。
A Dual Mystery Revealed by Radio Waves and X-Rays
无线电波与 X 射线揭示的双重谜团
These observations have revealed that radio bursts and x-ray emissions are generated by different mechanisms. When the white dwarf accretes gas from its companion, that gas is heated and emits x-rays. At the same time, powerful radio bursts occur in the region where the magnetic fields of the two stars interact. However, since the peaks of the radio and x-ray emissions do not coincide, it is believed that they are generated at different locations within the system.
这些观测结果揭示了无线电爆发和 X 射线辐射是由不同的机制产生的。当白矮星从伴星吸积气体时，气体被加热并发出 X 射线。与此同时，在两颗恒星磁场相互作用的区域会产生强大的无线电爆发。然而，由于无线电和 X 射线辐射的峰值并不重合，因此认为它们是在系统内的不同位置产生的。
Regarding x-rays, data from the Chinese Academy of Sciences’ Einstein Probe observation satellite revealed radiation with a period of approximately 1.32 hours. According to the researchers, the large amplitude of the x-ray fluctuations suggests that the accretion rate onto the white dwarf is likely changing over time.
关于 X 射线，来自中国科学院“爱因斯坦探针”卫星的数据显示，其辐射周期约为 1.32 小时。研究人员表示，X 射线波动幅度较大，表明白矮星的吸积率很可能随时间而变化。
ASKAP J1745-5051 is the third LPT detected in x-rays. It is the second LPT to exhibit regular x-ray emission, and this is the first time it has been confirmed that this regularity stems from the orbital motion of a binary system.
ASKAP J1745-5051 是第三个在 X 射线波段探测到的 LPT。它是第二个表现出规律性 X 射线辐射的 LPT，并且这是首次证实这种规律性源于双星系统的轨道运动。
The radio signal itself also exhibits characteristics not previously observed in LPTs. The pulses are elliptically polarized, and the upper end of the emitted frequency fluctuated up and down in sync with a longer-period beat. It is possible that this “beat” originates from the misalignment between the white dwarf’s rotation and its orbital motion, though the rotation period could not be determined in this study.
无线电信号本身也表现出此前在 LPT 中未曾观察到的特征。脉冲呈椭圆偏振，且发射频率的上限随一个长周期的“拍频”上下波动。这种“拍频”可能源于白矮星自转与轨道运动之间的错位，尽管本研究未能确定其自转周期。
In addition, a phenomenon known as “modulation lanes”—in which the intensity of the pulses is modulated in a striped pattern—was also observed. This is reportedly the first time this phenomenon has been detected in a binary system (a system of two celestial bodies gravitationally bound to each other) other than the Jupiter-Io system.
此外，还观察到了一种被称为“调制带”（modulation lanes）的现象，即脉冲强度以条纹状模式进行调制。据报道，这是除木星-木卫一系统外，首次在双星系统（两个受引力束缚的天体系统）中探测到该现象。
The Rosetta Stone of the Universe
宇宙的“罗塞塔石碑”
Researchers regard ASKAP J1745-5051 as a crucial reference object for deciphering LPTs. Rose emphasizes that this discovery could function like the Rosetta stone—which was key to deciphering ancient hieroglyphs—in determining whether other LPTs are associated with neutron star pulsars or white dwarf systems.
研究人员将 ASKAP J1745-5051 视为解读 LPT 的关键参考对象。Rose 强调，这一发现可能就像解读古埃及象形文字的关键——“罗塞塔石碑”一样，有助于确定其他 LPT 是与中子星脉冲星有关，还是与白矮星系统有关。
“Some similar objects had been linked to binary systems before, but this is the first one where we can clearly see both stars and the accretion process in action,” said Tara Murphy, head of the Department of Physics at the University of Sydney, in a press release.
“此前也有一些类似天体被认为与双星系统有关，但这是我们第一次能够清晰地看到两颗恒星以及正在进行的吸积过程，”悉尼大学物理系主任 Tara Murphy 在新闻发布会上说道。
Star systems like ASKAP J1745-5051 could serve as natural laboratories for studying the behavior of matter under strong magnetic fields and gravitational forces.
像 ASKAP J1745-5051 这样的恒星系统，可以作为研究物质在强磁场和引力作用下行为的天然实验室。