Chemically Peculiar/Magnetic Stars and the a photometry

Hans Michael Maitzen, Ernst Paunzen

Institute for Astronomy, University of Vienna

Properties

Strong magnetic field implies chemical peculiarity

Spectral range: B0 - F2Low rotational velocitiesVariability about 5% of all stars in this spectral range

Notation according to Preston

Group Designation Magnetic field Spectral type

CP1 Am no B9 – F4

CP2 Ap Si, Cr, Eu, Sr strong B6 – F2

CP3 Ap Hg, Mn weak B5 – A0

CP4 He-weak weak/strong B2 – B8

He-strong weak/strong B0 – B4

Bootis no B9 – F2

History facts I

1897: Detection by Antonia Maury 1914: Guthnik and Prager observe for the first

time the light curve of the prototype star 2 CVn

1933: Morgan finds correlation between temperature and chemical composition

1947: Babcock discovers magnetic fields 1950: Stibbs develops the Oblique Rotator

Theory

History facts II 1958: Deutsch publishes the first abundance maps of the

surface for peculiar stars 1968: Kodaira discovers flux depressions at 4100Å, 5200Å

and 6300Å 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

Dynamo Theory: Rotation produces self induction

Theory of the fossil magnetic field:interstellar origin

pre-main sequence evolution

Characteristics of magnetic fields

DipoleQuadrupoleRotational axis

agnetic axis

300 G Heff 40 kG

Sun: 10 G (up to 4000 G) Jupiter: 5 - 20 GEarth: 0.3 - 0.6 G

An example

Corona Borealis

a Photometry a = g2 - [(g1 + y)/2]

a = a(star) - a0

a Photometry of open clusters

a Photometry in the LMC - NGC 1866

Galactic ejection path of HIP 60350

The graph shows the way of the ejected B4V star HIP 60350

Path from the lower left (close to NGC 3603) to the upper right in the vicinity of the Sun

Present LSR velocity 417 km s-1