Transcript Chemically Peculiar/Magnetic Stars and the a photometry

Chemically Peculiar/Magnetic Stars
and the Da photometry
Hans Michael Maitzen, Ernst Paunzen
Institute for Astronomy, University of Vienna
Properties
 Strong
magnetic field implies chemical
peculiarity
 Spectral range: B0 - F2
 Low rotational velocities
 Variability
 about 5% of all stars in this spectral range
Notation according to Preston
Group
Designation
Magnetic field Spectral type
CP1
Am
no
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
B9 – F4
History facts I
 1897:
Detection by Antonia Maury
 1914: Guthnik and Prager observe for the first
time the light curve of the prototype star
a2 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 Da observations published
 2001: First chemically peculiar stars detected in
the LMC by Da 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
 Dipole
 Quadrupole
axis 
Magnetic axis
 300 G Heff 40 kG
 Sun: 10 G (up to
4000 G)
 Jupiter: 5 - 20 G
 Earth: 0.3 - 0.6 G
 Rotational
An example
bCorona Borealis
Da Photometry

a = g2 - [(g1 + y)/2]
Da
= a(star) - a0
Da Photometry of open clusters
Da 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