Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Spiral shocks in the accretion disc of IP Peg during outburst maximum   In response to our recent discovery of spiral arms in the accretion disc of
IP Peg during rise to outburst, we have obtained time-resolved
spectrophotometry of IP Peg during outburst maximum. In particular, indirect
imaging of HeII 4686, using Doppler tomography, shows a two-arm spiral pattern
on the disc image, which confirms repeatability over different outbursts. The
jump in HeII intensity (a factor of more than two) and in velocity (~200--300
km/s) clarifies the shock nature of the spiral structure. The HeII shocks show
an azimuthal extent of ~90 degrees, a shallow power-law emissivity ~V^{-1}, an
upper limit of 30 degrees in opening angle, and a flux contribution of 15 per
cent of the total disc emission. We discuss the results in view of recent
simulations of accretion discs which show that spiral shocks can be raised in
the accretion disc by the secondary star.

21
The categories of this paper are: adap-org
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
22
The categories of this paper are: chao-dyn
23
The categories of this paper are: solv-int
0
The categories of this paper are: hep-ph
4
The categories of this paper are: cond-mat
31
The categories of this paper are: ao-sci
30
The categories of this paper are: q-alg
5
The categories of this paper are: gr-qc
10
The categories of this paper are: q-bio
28
The categories of this paper are: alg-geom
12
The categories of this paper are: nucl-th
3
The categories of this paper are: physics
7
The categories of this paper are: hep-th