DY Persei variables are a subclass of
R Coronae Borealis (R CrB) variables. They are
carbon
Carbon () is a chemical element with the symbol C and atomic number 6. It is nonmetallic and tetravalent—its atom making four electrons available to form covalent chemical bonds. It belongs to group 14 of the periodic table. Carbon mak ...
-rich
asymptotic giant branch (AGB) stars that exhibit
pulsational variability of AGB stars and
irregular fades similar to R CrB stars.
The star
DY Persei
DY Persei is a variable star and carbon star in the Perseus constellation. At maximum it is 11th magnitude and at its faintest it drops to 16th magnitude. DY Persei is the prototype of the very rare DY Persei class of variables that p ...
is the prototype of this tiny class of variable stars. Only DY Persei itself was known in our galaxy until 2008 when systematic catalogue searches for R CrB variables discovered a 17th magnitude (at maximum) example.
Since then automated searches have confirmed another four, including one of magnitude 5.9 at maximum.
There are also several candidates that have not yet been observed to fade, and several DY Per stars in the
Large Magellanic Cloud.
Although DY Persei variables have been considered a subset of the R CrB variables because of their irregular fades and carbon-rich spectra, they may simply be an unusual type of
carbon star unrelated to the more massive and more luminous R CrB variables. The fades may be caused by obscuring ejection events rather than carbon condensation in the atmospheres of the stars.
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References
{{Variable star topics
Variable stars
Pulsating variables