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Rapidly Oscillating Ap Stars
Rapidly oscillating Ap stars (roAp stars) are a subtype of the Ap star, Ap star class that exhibit short-timescale rapid Photometry (astronomy), photometric or radial velocity variations. The known periods range between 5 and 23 minutes. They lie in the Delta Scuti variable, δ Scuti instability strip on the main sequence. Discovery The first roAp star to be discovered was HD 101065 (Przybylski's Star) in 1961. The oscillations were discovered by Donald Kurtz using the telescope at the South African Astronomical Observatory, who saw 10–20-millimagnitude variations in the light curve of the star with a period of 12.15 minutes. Classification The roAp stars are sometimes referred to as rapidly oscillating α2 Canum Venaticorum variables. Both the roAp stars and some Alpha2 Canum Venaticorum variable, α2 CVn variables lie on the δ Scuti instability strip and are magnetic chemically peculiar stars, but the roAp stars have very short periods less than an hour. Oscillations The roA ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ap Star
Ap and Bp stars are chemically peculiar stars (hence the "p") of spectral types A and B which show overabundances of some metals, such as strontium, chromium, or europium. In addition, larger overabundances are often seen in praseodymium and neodymium. These stars have a much slower rotation than normal for Stellar classification#Class B, A- and B-type stars, although some exhibit rotation velocities up to about 100 kilometers per second. Magnetic fields Ap and Bp stars have stronger magnetic fields than classical A- or B-type stars; in the case of HD 215441, reaching 33.5 kGauss (unit), G (3.35 Tesla (unit), T). Typically the magnetic field of these stars lies in the range of a few kG to tens of kG. In most cases a field which is modelled as a simple dipole is a good approximation and provides an explanation as to why there is an apparent periodic variation in the magnetic field, as if such a field is not aligned with the rotation axis—the field strength will change as ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |