Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Swift Supergiant Fast X-ray Transients Project: recent results   We present an overview of our Supergiant Fast X-ray Transients (SFXT)
project, that started in 2007, by highlighting the unique observational
contribution Swift is giving to this exciting new field. By means of outburst
detection with Swift/BAT and follow-up with Swift/XRT, we demonstrated that
while the brightest phase of the outburst only lasts a few hours, further
significant activity is observed at lower fluxes for a considerably longer
(weeks) time. After intense monitoring with Swift/XRT, we now have a firm
estimate of the time SFXTs spend in each phase. The 4 SFXTs we monitored for
1-2 years spend between 3 and 5 % of the time in bright outbursts. The most
most probable flux level at which a random observation will find these sources,
when detected, is F(2-10 keV) ~ 1-2E-11 erg cm^{-2} s^{-1} (unabsorbed),
corresponding to luminosities of a few 10^{33} to a few 10^{34} erg s^{-1}.
Finally, the duty-cycle of inactivity ranges between 19 and 55 %.

21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
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The categories of this paper are: chao-dyn
16
The categories of this paper are: stat
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
25
The categories of this paper are: patt-sol
5
The categories of this paper are: gr-qc
35
The categories of this paper are: mtrl-th
31
The categories of this paper are: ao-sci
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The categories of this paper are: atom-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: supr-con
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The categories of this paper are: q-alg
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The categories of this paper are: quant-ph
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The categories of this paper are: q-fin