Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Doppler maps and surface differential rotation of EI Eri from the
  MUSICOS 1998 observations   We present time-series Doppler images of the rapidly-rotating active binary
star EI Eri from spectroscopic observations collected during the MUSICOS
multi-site campaign in 1998, since the critical rotation period of 1.947 days
makes it impossible to obtain time-resolved images from a single site. From the
surface reconstructions a weak solar-type differential rotation, as well as a
tiny poleward meridional flow are measured.

23
The categories of this paper are: solv-int
26
The categories of this paper are: bayes-an
20
The categories of this paper are: acc-phys
18
The categories of this paper are: econ
12
The categories of this paper are: nucl-th
17
The categories of this paper are: q-fin
34
The categories of this paper are: chem-ph
8
The categories of this paper are: hep-ex
27
The categories of this paper are: comp-gas
32
The categories of this paper are: atom-ph
7
The categories of this paper are: hep-th
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
22
The categories of this paper are: chao-dyn
9
The categories of this paper are: nlin