The main star will "absorb the star Dafa" Guo Shoujing telescope found a rare new type of cataclysmic variable star

Source: Science and Technology Daily

The stars shining in the night sky will also "absorb the stars dafa"?

On August 29, the reporter learned from the National Astronomical Observatory of the Chinese Academy of Sciences that based on the observation data of the Guo Shoujing Telescope (LAMOST), researchers found a very rare new type of cataclysmic variable star. The object is named LAMOST J0140355+392651, and its companion is in the transition phase of evolution to an extremely low-mass white dwarf. Previously, there have been theories predicting the existence of such transitional cataclysmic variables, but the astronomical community has never observed such transitional radical variables.

The rare type of cataclysmic variable star successfully captured by the Guo Shoujing telescope confirms the existence of such a transitional cataclysmic variable star, and provides substantial evidence for further understanding the formation and evolution history of the cataclysmic variable star. The relevant research results are published online in the international academic journal "Royal Astronomical Society Monthly Journal".

White dwarf main star will "absorb the star Dafa"

The so-called radical variable star refers to a type of celestial body with a dual identity, which is both a binary star and a variable star. Cataclysmic variable stars are uniquely positioned to study many of the frontiers of stellar physics. The main star of a typical cataclysmic variable star is a white dwarf , and the companion star is usually a late-type main sequence star , or in special cases an evolving giant or even a white dwarf.

"As a binary system, cataclysmic variable stars have very short orbital periods, most of which are no longer than 10 hours; cataclysmic variable stars also have the characteristics of variable stars, and their brightness changes significantly over time." Zhao Yongyong, a researcher at the National Astronomical Observatory of the Chinese Academy of Sciences, said.

Interestingly , in most cataclysmic variable stars , the white dwarf host star also " absorbs the star " , and there is a constant transfer of material between it and its main sequence companion. "Specifically, the gluttonous host star continuously ascites and swallows material from the more massive companion star and forms an accretion disk around the host star." Zhao Yongyong explained.

So how do astronomers search for such objects?

Zhao Yongyong said that as a binary star system, catapult variable stars show significant emission characteristics on the spectrum; as variable stars, cataclysmic variable stars have obvious star magnitude changes in luminosity; these unique properties provide traceable observational basis for searching for this special celestial body.

"To date, researchers have searched for cataclysmic variable stars by light change, spectral signatures, and color, and the discovery of cataclysmic variable samples has come from a variety of different sources, and the most direct and effective method is to use the explosive characteristics of cataclysmic variable stars, especially dwarf novae." Zhao Yongyong said that the Guo Shoujing telescope's large-scale spectral survey project provides superior resources for using spectral characteristics to search for cataclysmic variable stars.

Based on the spectral database of Guo Shoujing's telescope, the researchers conducted a comprehensive search for cataclysmic variable stars, and found a total of 245 cataclysmic variable stars, which greatly enriched the existing samples of cataclysmic variable stars.

Zhao Yongyong said that as more and more samples of radical variable stars are discovered, some of the extremely rare or even only appear in theoretical predictions of the members of the radical variable stars have been excavated, and these sword-and-edged cathetly variable stars are constantly refreshing astronomers' understanding of such objects.

Special stars that challenge traditional laws

In the binary system of the radical variable star, the white dwarf host star that will "absorb the star dafa" continuously accrues the material of the companion star. This constant exchange of matter plays a crucial role in the evolution of cataclysmic variable stars.

Studies have shown that for most cataclysmic variable stars with an orbital period of less than 6 hours, the properties of the companion star's mass, radius, temperature, luminosity and mass loss rate have a certain empirical relationship with the orbital period of the binary star system.

"This empirical relationship can be said to be the baton for the study of short-period flux variable stars, we can obtain the orbital period of binary stars through light curves or time series spectroscopic observations, and with the orbital period, we can deduce other properties of the cataclysmic variable stars through this empirical relationship." Zhao Yongyong said that the empirical laws possessed by companion stars have also proved to be very useful for verifying and calibrating the binary star mass transfer model.

But unfortunately, this seemingly very useful law between the properties of the companion star and the orbital period was broken by the special cataclysmic variable star newly discovered by the Guo Shoujing telescope.

"The newly discovered unusual cataclysmic variable star, with an orbital period of 3.81 hours, belongs to the category of short-period flux variable stars, but its temperature, mass and the orbital period of the corresponding binary star are completely inconsistent with the empirical laws of traditional companion stars." Zhao Yongyong said.

This has forced astronomers to re-examine the identity of this particular star.

To fully determine its orbit and associated properties, the team analyzed it using multiple telescope observations and eventually found that the new object was a rare, evolutionary transition cataclysmic variable star whose companion star was not a main sequence star, but an expanding star's helium nucleus.

Based on the binary evolutionary model, the researchers speculate that the companion star of the cataclysmic variable star began to transfer mass to the white dwarf host star, which had already ended the main sequence stage and underwent a significant evolutionary process.

In addition, using evolutionary model calculations, the researchers predict that the mass transfer of this binary star will soon end, after which the companion will evolve into an extremely low-mass white dwarf. "That is, the companion of this cataclysmic variable star is in a transition state between a star's helium nucleus and an extremely low-mass white dwarf." Zhao Yongyong added.

Zhao Yongyong stressed that the existence of such a transitional radical variable star had been predicted theoretically, but it had never been observed, and the Guo Shoujing telescope had observed its existence for the first time with its advantages in searching for rare celestial objects. (Lu Chengkuan)