Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Swift observations of high-redshift radio-loud quasars   We report on Swift observations of four z>2 radio-loud quasars (0212+735,
0537-286, 0836+710, and 2149-307), classified as blazars. The sources,
well-known emitters at soft-medium X-rays, were detected at >5sigma with the
BAT experiment in 15-150 keV. No flux variability was detected within the XRT
and BAT exposures, with the exception of 0836+710 which shows an increase of a
factor 4 of the 15-150 keV flux on a timescale of one month. The 0.3-10 keV
spectra are well fitted by power law models, with rather hard continua (photon
indices Gamma_XRT ~1.3-1.5); similarly, the 15-150 keV spectra are described by
power laws with Gamma_BAT ~1.3-1.8. The XRT data exhibit spectral curvature,
which can be modeled either in terms of excess absorption along the line of
sight, or a downward-curved broken power law. In the former case, if the excess
N_H is at the rest-frame of the source, columns of N_H^z=(0.3-6)x10^22 cm^-2
are measured. Modeling of the SEDs of the four quasars shows that the emission
at the higher frequencies, >~ 10^16 Hz, is dominated by the jet, while the
steep optical-to-UV continua, observed with the UVOT, can be attributed to
thermal emission from the accretion disk. The disk luminosity is between 1% and
10% the jet power, similar to other powerful blazars.

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The categories of this paper are: solv-int
27
The categories of this paper are: comp-gas
11
The categories of this paper are: hep-lat
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
19
The categories of this paper are: eess
7
The categories of this paper are: hep-th
34
The categories of this paper are: chem-ph
9
The categories of this paper are: nlin
25
The categories of this paper are: patt-sol
2
The categories of this paper are: math
36
The categories of this paper are: cmp-lg