What is a Flare Star?

A flaring star is a variable star. Its brightness often has unpredictable huge changes. Sometimes it changes more than a few magnitudes in a few minutes, and it gradually recovers after a few minutes to several hours. The reason for the change in brightness is due to a large-scale flare burst on the surface of the star's chromosphere. The change in the spectral range is wide, spanning radio waves to x-rays. Such flares can also be observed in the sun, but the energy scale is not so large.

[yào xng]

Yaoxing is a special kind

The bright star, also known as the whale UV-type star, its brightness is basically unchanged in ordinary times, and sometimes it suddenly increases suddenly in minutes or even seconds, and the luminosity varies from a few tenths to several magnitudes. Individuals can reach more than 10 magnitudes, and then slowly recover after tens of minutes. This phenomenon is called "Yao Liang" or "Yao Change". As early as 1924, the DH star of the ship's base was found to be bright, but it did not attract enough attention at that time. In 1948, it was discovered that the luminosity of the constellation UV star increased 11 times in 3 minutes, and later a number of constellation UV-type constellation stars from dKe to dMe were discovered.

Most of the observations are flares near the sun. After years of international joint observations, a lot of data has been accumulated in the visible light, radio, and X-ray bands. The main characteristic of Yaoxing is that in the wide band when Yao Yao is bright, radiation can be measured from X-rays of 1 to 7 thousand electron volts to radio waves of about 196 MHz, both continuous radiation and emission lines. In the optical band, generally, the ultraviolet amplitude is the largest, followed by blue light, and yellow light is the smallest. There is no correlation between the amplitude of radiation in different bands, that is, several bands may not appear bright at the same time. There is also no correlation between different types of radiation (continuous spectrum or emission lines).

The distribution of Yaoliang over time is similar to the Poisson distribution (the same is true for the observation of the Pleiades cluster star). The light curve consists of two parts, "fast" and "slow". "Fast" corresponds to continuous radiation, and "slow" corresponds to the emission line. The emission lines mainly include hydrogen, ionized calcium, helium, etc. The color index U-B and B-V when the light is bright may vary widely. The spectral index of radio radiation is also the same. The average energy emitted when it shines is related to the luminosity of the star.

The light curve type is also related to photometric. Observation of the photoelectric spectrum of the eclipsed binary star Gemini YY (both sub-stars are flares) shows that there is a local active area on the surface of the star. Yaoliang occurred in the active area, and multiple Yaoliang could occur in the same active area. Spectral observations of more than ten years for some flares show that the annual average intensity of their emission lines changes slowly, with a period similar to that of the sun. The flares of flares near the sun are similar in nature to the flare activity of the sun, but on a much larger scale than the solar flare activity.

Nearly 100 bright stars have been found near the sun, including the Centaurus neighbor. After years of observation, flares have also been found in some star clusters or associations. For example, more than 460 have been found in the Pleiades region, more than 300 have been found in the Orion Nebula region, more than 50 have been found in the North American Nebula region, and more than 30 have been found in the Ghost Cluster area. These flares are mainly available Let us study the evolutionary relationship between star clusters of different ages and other types of celestial bodies.

In recent years, some so-called non-classical flares have also been discovered, that is, the eclipsing binary star W Ursa Major Ursa, the close binary star Ursa Major UX star, the Gemini U-shaped star and the early star have all been found. Since there is no systematic search, the information is scarce and their nature is not clear.