DY Persei variable
Encyclopedia
DY Persei variables are a subclass of R Coronae Borealis
R Coronae Borealis
R Coronae Borealis is a yellow supergiant star, and is the prototype of the RCB class of variable stars, which fade by several magnitudes at irregular intervals...

 variables. They are carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...

-rich asymptotic giant branch
Asymptotic Giant Branch
The asymptotic giant branch is the region of the Hertzsprung-Russell diagram populated by evolving low to medium-mass stars. This is a period of stellar evolution undertaken by all low to intermediate mass stars late in their lives....

 stars that exhibit pulsational variability of AGB stars and irregular variability
Irregular variable
An irregular variable is a type of variable star in which variations in brightness show no regular periodicity. There are two main sub-types of irregular variable: eruptive and pulsating.Eruptive irregular variables are divided into three categories:...

 of RCB stars.

The star DY Persei
DY Persei
DY Persei is a variable star in the Perseus constellation, being a prototype star to the very rare type of DY Persei variables, that pulsate like red variables, but also fade from sight like R Coronae Borealis variables....

is the prototype of this tiny class of variable stars.
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