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Tianqin RR type star

Pulsating variable star
synonym Short period Cepheid variable (Astronomical terminology) generally refers to the RR type star of Lyra
RR Lyr star, Also known as cluster variable stars, Pulsating variable star Type A-F SuperStar Photoperiod 0.2-1.2 days, Light amplitude 0.2—2 Visual magnitude , of Star Family II , on Herotu A fixed region in the middle of the horizontal branch. Many of these stars appear in the Globular cluster Li. [2]
Chinese name
Tianqin RR type star [2]
Foreign name
RR Lyr star [2]
RR Lyrae type variable stars
Distribution
Galactic surface Silver halo And globular clusters
Luminosity
Relatively high
Constellation
Lyra

brief introduction

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Two kinds of variable stars Herotu Upper position: the blue area marked RR represents RR type Lyra variable, and the red area marked C represents Cepheid variable. RR type Lyra variable, also known as cluster variable, is a kind of pulsating variable. It has a similar circumference relationship (but not obvious) with Cepheid variable, and can be used to measure distance. The brightest variable star of this type is RR Lyra, hence its name. [1]
gross Pulsating variable star On the Herot chart, it is located in a long and narrow unstable zone, and RR type Lyra variable stars are located in the middle and lower part of this unstable zone. Most of the spectral types are A type, and a small part are F type, with almost the same absolute magnitude. Because the RR type Lyra variable was early Globular cluster It is also called cluster variable star. The total number of RR type Lyra variables discovered is about 1/4 of pulsating variables. [1]
Two kinds of variable stars Herotu Upper position: the blue area marked RR represents RR type Lyra variable, and the red area marked C represents Cepheid variable. RR type Lyra variable, also known as cluster variable, is a kind of pulsating variable. It has a similar circumference relationship (but not obvious) with Cepheid variable, and can be used to measure distance. The brightest variable star of this type is RR Lyra, hence its name. According to the pulsation pattern, RR type Lyra variables are mainly divided into three categories, namely RRab, RRc and RRd. RRab pulsates with fundamental frequency, RRc pulsates with first-order harmonic frequency, and RRd occurs simultaneously, that is, double period RR Lyra variable stars, The light change curve of RRab type is asymmetric, the light change period is relatively long (0.55 days on average), and the photometric change is relatively large (more than 0.5, etc.), while the light change curve of RRc type is almost symmetrical, close to the sine curve, the light change period is relatively short (0.3 days on average), and the photometric change is relatively small (less than 0.5, etc.). [1]

distribution

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RR type Lyra variable stars in the Milky Way are widely distributed in Galactic surface Silver halo And globular clusters. Because of their relatively high luminosity, they are relatively easy to identify and observe. RR Lyra variable can be used to measure the Milky Way Globular cluster As well as the distance between neighboring galaxies Age , stellar evolution, galactic dynamics and evolution. You can also Cepheid variable The measured distance shall be independently calibrated. [1]
The distribution range of these variable stars and their small mass (usually only 60% - 80% of the sun's) prove that they are old stars. Some even reached 12 billion years old, almost the same age as the universe. They have a large radius, usually 4-6 times that of the sun, so their luminosity is still bright. These stars are the template for the later evolution of small and medium-sized stars. They have gone through the red giant stage, gradually shrinking and becoming hot, and will eventually become hot white dwarfs.

Research findings

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On June 20, 2023, the National Astronomical Observatory of the Chinese Academy of Sciences announced that a new study led by Chen Xiaodian, an associate researcher of the observatory, found that the double cycle "RR Lyra variable star" is the best known "standard candle" in the universe. Using its two cycles to measure the distance of the star system no longer requires information on element abundance, This method enables high-accuracy ranging of galaxies in batches. [3]