Chemically Peculiar/Magnetic Stars and the  a photometry Hans Michael Maitzen, Ernst Paunzen Institute for Astronomy, University of Vienna

Properties F Strong magnetic field implies chemical peculiarity F Spectral range: B0 - F2 F Low rotational velocities F Variability F about 5% of all stars in this spectral range

Notation according to Preston

History facts I F 1897: Detection by Antonia Maury  1914: Guthnik and Prager observe for the first time the light curve of the prototype star  2 CVn F 1933: Morgan finds correlation between temperature and chemical composition F 1947: Babcock discovers magnetic fields F 1950: Stibbs develops the Oblique Rotator Theory

History facts II F 1958: Deutsch publishes the first abundance maps of the surface for peculiar stars F 1968: Kodaira discovers flux depressions at 4100Å, 5200Å and 6300Å F 1974: Preston introduces a new classification scheme for peculiar stars which is still in use  1976: First  a observations published  2001: First chemically peculiar stars detected in the LMC by  a photometry

Classification resolution spectroscopy

Origin of magnetic fields F Dynamo Theory: Rotation produces self induction F Theory of the fossil magnetic field: interstellar origin pre-main sequence evolution

Characteristics of magnetic fields F Dipole F Quadrupole  Rotational axis   agnetic axis  300 G  H eff  40 kG F Sun: 10 G (up to 4000 G) F Jupiter: G F Earth: G

Variability – Magnetic field

An example

 Corona Borealis

 a Photometry F a = g2 - [(g1 + y)/2]   a = a(star) - a 0

 a Photometry of open clusters

 a Photometry in the LMC - NGC 1866

 a Photometry of globular clusters

Galactic ejection path of HIP F The graph shows the way of the ejected B4V star HIP F Path from the lower left (close to NGC 3603) to the upper right in the vicinity of the Sun F Present LSR velocity 417 km s -1