Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Do Magnetic Fields Prevent Hydrogen from Accreting onto Cool Metal-line
  White Dwarf Stars?   It is generally assumed that metals detected in the spectra of a few cool
white dwarfs cannot be of primordial origin and must be accreted from the
interstellar medium. However, the observed abundances of hydrogen, which should
also be accreted from the interstellar medium, are lower than expected from
metal accretion. Magnetic fields are thought to be the reason for this
discrepancy. We have therefore obtained circular polarization spectra of the
helium-rich white dwarfs GD40 and L745-46A, which both show strong metal lines
as well as hydrogen. Whereas L745-46A might have a magnetic field of about
-6900 G, which is about two times the field strength of 3000G necessary to
repell hydrogen at the Alfen radius, only an upper limit for the field strength
of GD40 of 4000G (with 99% confidence) can be set which is far off the minimum
field strength of 144000G to repell hydrogen.

0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
7
The categories of this paper are: hep-th
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
19
The categories of this paper are: eess
2
The categories of this paper are: math
3
The categories of this paper are: physics
22
The categories of this paper are: chao-dyn
15
The categories of this paper are: nucl-ex
30
The categories of this paper are: q-alg
1
The categories of this paper are: cs
13
The categories of this paper are: quant-ph
37
The categories of this paper are: supr-con
32
The categories of this paper are: atom-ph