Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The absence of a thin disc in M81   We present the results of simultaneous Suzaku and NuSTAR observations of the
nearest Low-Luminosity Active Galactic Nucleus (LLAGN), M81*. The spectrum is
well described by a cut-off power law plus narrow emission lines from Fe
K$\alpha$, Fe XXV and Fe XXVI. There is no evidence of Compton reflection from
an optically thick disc, and we obtain the strongest constraint on the
reflection fraction in M81* to date, with a best-fit value of $R = 0.0$ with an
upper limit of $R < 0.1$. The Fe K$\alpha$ line may be produced in optically
thin, $N_H = 1 \times 10^{23}$ cm$^{-2}$, gas located in the equatorial plane
that could be the broad line region. The ionized iron lines may originate in
the hot, inner accretion flow. The X-ray continuum shows significant
variability on $\sim 40$ ks timescales suggesting that the primary X-ray source
is $\sim 100$s of gravitational radii in size. If this X-ray source illuminates
any putative optically thick disc, the weakness of reflection implies that such
a disc lies outside a few $\times 10^3$ gravitational radii. An optically thin
accretion flow inside a truncated optically thick disc appears to be a common
feature of LLAGN that are accreting at only a tiny fraction of the Eddington
limit.

22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin
29
The categories of this paper are: funct-an
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
33
The categories of this paper are: plasm-ph
36
The categories of this paper are: cmp-lg
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
18
The categories of this paper are: econ