Millisecond pulsar (MSP)[1], once called "Repetitive pulsar", is a pulsar whose rotation period is within the range of 1 to 10 milliseconds. It can onlymicrowaveorX-rayOfelectromagnetic wavespectrumWas observed on the.
The origin of millisecond pulsars is still somewhat mysterious. The dominant theory believes that they were originally pulsars with long periodsaccretion Extension or reply of.For this reason, low-quality X-rayKonductraThey are thought to be pulsars in the process of recovery.
Such pulsars emitting X-rays are considered to be accelerating, and their activity is increasing.They may be absorbingRoche valveThe overflow angular momentum increases the speed of rotation to hundreds of revolutions per second, and the neutron star is accelerated.The accelerated millisecond pulsar emits electromagnetic wave spectrum inlong waveLong part.
Many millisecond pulsars areGlobular clusterBecause the extremely high stars in these systemsdensityIt is conducive to creating an environment that can cause mass exchange between binary stars, so that the rotating neutron star can reduce its period to become a millisecond pulsar through interaction.There are about 130 millisecond pulsars found in globular clusters, 33 in Terzan 5 alone, and thenRhododendron47, 22,M28andM158 for each.
Speed limit
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The first millisecond pulsar, PSR B1937+21, was discovered in 1982 with a rotational speed of 641 revolutions per second. Its radiation falls on the radio band, but it has the title of fastest rotating neutron star for only about 180 days.The PSR J1748-2446ad discovered in 2005 is the fastest rotating neutron star known so far (2006), with 716 revolutions per second.
Based on the current theory of neutron star structure and evolution, it is predicted that the limit of pulsar rotation speed is as follows:
Their rotation cannot exceed 1500 revolutions per second, and they may split if they do;
Before reaching this high speed rotation, it will radiateGravity wave, inhibit the increase of speed before being further accelerated.In fact, the speed seems to have been suppressed within 1000 revolutions per second (corresponding to a period of 1 millisecond).
Indeed, by the end of 2006, no sub millisecond pulsars had been found, and the fastest rotating speed was 716 Hz.This suggests that the energy loss caused by the radiation of gravity waves does indeed have a braking mechanism on the high-speed rotating neutron star.
However, in early 2007International Gamma Ray Astrophysics LaboratoryIt points out that the neutron star XTE J1739-285 rotates 1122 times per second.However, this result is not statistically significant, because it falls within the standard deviation of 3, so it is only regarded as an interesting candidate, and the result is only for reference.However, gravitational radiation is believed to play a role in slowing down the rotation rate.Moreover, IGR J00291+5934, an X-ray pulsar with a rotating speed of 599 revolutions per second, which was discovered earlier, is still the first sequential candidate most likely to generate gravity waves. In the future, gravity waves are most likely to be detected, because most X-ray pulsars only rotate at about 300 revolutions per second.
Latest findings
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National Astronomical Observatory Discovers Two New Millisecond Pulsars
Pulsar search isRadio astronomyAs an important basic frontier field in astronomy, it has led to many revolutionary discoveries, such as millisecond pulsars, exoplanets, massive neutron stars and rapid radio bursts.National Astronomical Observatory, Chinese Academy of SciencesPan Zhichen, a doctoral candidate, and his supervisor, Researcher Li Di, used the long-term monitoring data of Parkes telescope provided by George Hobbs, a senior visiting scholar of the Chinese Academy of Sciences and a scientist of the Commonwealth Scientific and Industrial Research Organization of Australia, and cooperated to develop the spectral incoherent superposition search method, successfully finding two new millisecond pulsars in the Rhododendron 47 globular cluster,They are named J0024-7204aa and J0024-7204ab.hold47 Tucanae Globular clusterThe number of known pulsars has been updated from 23 to 25.This is the first time that domestic scholars have published newRadio pulsar, published in the monthly journal of the Royal Astronomical Society MNRAS letter (MNRAS459, L26 – L30).Wang Pei, assistant researcher of the National Astronomical Observatory, is one of the article collaborators[2]。
The key to this discovery is to integrate the 1100 hours of observation data accumulated over the years and make the time-domain signals observed for many timesFourier transformation The power spectrum is aligned and accumulated in the frequency domain to effectively improve the signal-to-noise ratio and help detect weaker pulsar signals.The dispersion value of J0024-7024aa is the largest in Rhododendron 47, and its rotation period is 1.84 milliseconds, which is the shortest in Rhododendron 47, ranking 12th among all pulsars.Globular clusterRich in millisecond pulsars and pulsar binary systems, it is an important observation target of FAST.According to the characteristics of repeated observation in FAST's early drift survey, the application of incoherent stack method can improve the detection capability of FAST pulsars.The researchers of the Interstellar Media Group of the National Astronomical Observatory have also quantified FAST's ability to scan and search for globular cluster pulsars and prepared relevant processing software, which will be detailed in another special article.
