Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Discovery of polarizations from ground state absorption lines: tracer of
  sub-Gauss magnetic field on 89Her   We report the identification of the polarization of ground state absorption
lines from post-AGB 89~Hercules. Two ground state neutral iron lines are found
to have counterintuitive high-amplitude polarizations and an unchanged
polarization direction through the orbital period, as opposed to the pattern of
polarizations of absorption lines from excited states, which are synchronized
with the orbital phase owing to optical pumping. This can be explained with
magnetic realignment on the ground state. The 3D mean magnetic field is thereby
unveiled from the degree and direction of the polarizations of the two iron
lines. The field strength is also constrained to be $\lesssim 100\,{\rm mG}$.
Our result has thus improved the accuracy by orders of magnitude compared to
the previous $10\,{\rm G}$ upper limit set by non-detection of the Zeeman
effect.

31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
2
The categories of this paper are: math
4
The categories of this paper are: cond-mat
19
The categories of this paper are: eess
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
3
The categories of this paper are: physics
25
The categories of this paper are: patt-sol
11
The categories of this paper are: hep-lat
12
The categories of this paper are: nucl-th
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex