Magnetic star[1-2]GeneralWith strong magnetic field, its magnetism can be directly through Zeeman effect, spectral line polarization, etcmeasureamountTo the star[3-4]。In the early stage, it mainly refers to medium and large mass stars (non degenerate stars) with magnetic fields, and later it also includes white dwarfs and neutron stars (degenerate stars).This concept originated from the measurement of stellar magnetic field. At that time, people only measured the magnetic field in a small number of medium and large mass stars, but most of them did not show observable magnetism.Therefore, there are magnetic stars and non magnetic stars.In the field of non degenerate stars, the concept of magnetic star has also beenuse[5-6]。According to the observation, only a small part of medium and large mass stars are still observablemagnetic field[7], most of them are special A and B type stars (Ap/Bp stars for short), with magnetic field of 300-30000 gauss;Very few are early B-type stars and O-type stars.
More than 30 years after the first measurement of the stellar magnetic field, astronomers have successively measured the magnetic field in degenerate stars and low mass stars, which are also classified asMagnetostar[3]。Among them, those with abnormal strong magnetic field in similar degenerate stars also have their own special names, such as magnetic field stronger than 10eightGauss white dwarfs are called polars;Usually stronger than 10thirteenThe neutron star with Gaussian magnetic field as its energy source is calledMagnetostarMagnetar, which is a novel extreme type in the magnetar family.
Magnetic field is a basic and important physical attribute of celestial bodies in both observation and theory, which affects the formation and evolution of celestial bodies and plays an important role in the rotation rate, chemical composition, mass loss, accretion, gas turbulence and other aspects of stars.The earliest measurement of the magnetic field of celestial bodies can be traced back to 1908. Hale measured the magnetic field of sunspots for the first timelevel[8]。The first time to measure the magnetic field of non solar objects was 40 years later: based on the Zeeman effect of spectral lines in the stellar spectrum, astronomer Babcock successfully measured the effective magnetic field of star 78Vir（Meridian magnetic field)[9]。This is also the prelude to the measurement of celestial magnetic field, and more and more related work has been done.By 1958, Babcock had compiled and published the firstMagnetostar list[10]。This list contains 89 magnetostars, 70 of which are Ap stars.With the deepening of observation, people have successively measured the magnetic fields of Bp stars, early B to O stars, white dwarfs and neutron stars.
Origin of magnetic field
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The origin of the magnetic field has not been determined, and the main mechanism islowertwospecies[3-4][11]：
1. The fossil field theory.For non degenerate stars, the compression and amplification of the interstellar magnetic field originated in the process of star formation;For degenerate stars, it originates from the compression and amplification of the magnetic field of the predecessor star.
twoGenerator theory（Dynamo theory）。See the generator theory entry.
scientific research
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The high-sensitivity observation of FAST in China also found repeated rapid radio bursts and polarization angle changes, revealing that the rapid radio bursts originated from magnetostars in the distant universe.[12]
