Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Variability of the iron K-emission line in the Seyfert 1 galaxy NGC 3516   We present strong evidence for variability of the flux of the iron K$\alpha$
emission line in the Seyfert 1 galaxy, NGC 3516. Two ASCA observations,
separated by $\sim 1$~yr, showed a marked decrease in continuum flux by $\sim
60$~per cent. The flux in the broad, iron K$\alpha$ line decreased by the same
factor in this time period, with no evidence for changes in the line profile.
The line variability is significant at $>99$~per cent confidence and rules out
models in which the line is produced in a molecular torus located at $>1$~pc
from the nucleus. An accretion disk is considerably more likely.

16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
24
The categories of this paper are: dg-ga
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
11
The categories of this paper are: hep-lat
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
35
The categories of this paper are: mtrl-th
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
28
The categories of this paper are: alg-geom
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics