Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Detailed Multifrequency Study of a Rapid VHE Flare of Mrk501 in May 2009   We present observations of the gamma-ray blazar Markarian 501 between April
17 and May 5, 2009, with the Whipple 10-m telescope, VERITAS, the Fermi Large
Area Telescope (LAT), Swift and RXTE as part of a 4.5-month multi-wavelength
campaign. The presentation will focus on the strong very high energy (VHE)
gamma-ray activity detected on May 1st with Whipple and VERITAS, when the
measured flux (E > 400 GeV) reached five times the flux of the Crab Nebula,
coincident with an increase in the optical polarization by a factor of 5, and a
rotation of the polarization angle by 15 degrees. We also show that, during
this 3-week period, the largest flux and spectral variability is seen at the
highest energies of the broadband spectral energy distribution.

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The categories of this paper are: supr-con
9
The categories of this paper are: nlin
5
The categories of this paper are: gr-qc
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
16
The categories of this paper are: stat
27
The categories of this paper are: comp-gas
3
The categories of this paper are: physics
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
2
The categories of this paper are: math
11
The categories of this paper are: hep-lat
20
The categories of this paper are: acc-phys
17
The categories of this paper are: q-fin
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex