What type of star is a delta Scuti variable RR Lyrae or Cepheid?
pulsating stars
Delta Scuti variables belong to the same family of pulsating stars as Cepheids and RR Lyrae stars – all these objects reside in the same instability strip in the Hertzsprung-Russell diagram.
What stars are in the instability strip?
The instability strip is a narrow, almost vertical region in the Hertzsprung-Russell diagram which contains many different types of variable stars (RR Lyrae, Cepheid variable, W Virginis and ZZ Ceti stars all reside in the instability strip).
Do Miras and Cepheids lie on the instability strip in an H-R diagram?
These in turn are a function of their mass and evolutionary stage. Cepheids, RR Lyraes, and Long Period Variables (LPVs) – Miras and Semiregulars – are pulsating variable stars and occupy regions on the H-R diagram called instability strips.
Where is the instability strip on the H-R diagram?
The Mira instability strip on the H-R diagram is the region between mid-sized stars on the main sequence and the giant branch. Semiregular variables are giants and supergiants showing periodicity accom- panied by intervals of semiregular or irregular light variation.
Why do variable stars pulsate in brightness?
Pulsating variable stars are intrinsic variables as their variation in brightness is due to a physical change within the star. In the case of pulsating variables this is due to the periodic expansion and contraction of the surface layers of the stars.
Why do RR Lyrae stars pulsate?
RR Lyrae stars pulse in a manner similar to Cepheid variables, but the nature and histories of these stars is thought to be rather different. Like all variables on the Cepheid instability strip, pulsations are caused by the κ-mechanism, when the opacity of ionised helium varies with its temperature.
Why are RR Lyrae stars useful distance indicators?
The importance of the study of RR Lyrae stars is at least threefold: first they can be used as “standard candles” in distance determinations, and secondly they provide us with information on the chemical composition (helium and heavy element abundance) in the halo and old disk popula- tion of our galaxy.
Do Miras and Cepheids lie on the instability strip in an HR diagram?
What is the brightness of a Delta Scuti variable?
Typical brightness fluctuations are from 0.003 to 0.9 magnitudes in V over a period of a few hours, although the amplitude and period of the fluctuations can vary greatly. The stars are usually A0 to F5 type giant or main sequence stars.
Why are Delta Scuti stars important to astronomers?
Some have amplitudes of nearly one magnitude and regular light curves like some of the RR Lyrae stars and Cepheid variables. Others have complex light curves and multiple periods with millimagnitude light variations. The delta Scuti stars are important astrophysically for many reasons.
When did the study of Delta Scuti begin?
The dwarf Cepheids or delta Scuti stars soon became a hot topic in stellar astronomical research. Theoretical modeling of pulsating variable stars commenced in the early 1960’s, as part of a general effort to use digital computers in stellar astrophysics, and an understanding of what delta Scuti stars were began to develop.
Can a Delta Scuti star cross the instability strip?
Delta scuti stars can cross the instability strip early or late in their lives, depending upon their masses. The Cepheid variables (which are more massive) cross the instability strip well away from the main sequence. The Sun will never cross the instability strip prior to becoming a red giant.