Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Extreme blazars   The recent Cherenkov telescope observations and detections of the BL Lac
objects Mkn 421, Mkn 501, 1ES 2344+514, PKS 2155--304 and possibly 1ES 1959+658
have shown that there exists a subclass of BL Lac objects emitting a
substantial fraction of their power between the GeV and the TeV bands. These
are the sources whose synchrotron spectrum peaks, in a $\nu$--$\nu F_{\nu}$
representation, in the EUV or X-ray band. Here I suggest that even more extreme
BL Lacs can exist, whose synchrotron spectrum peaks in the MeV band. These
sources should emit a substantial fraction of their power in the TeV band by
the inverse Compton process. Limits to the maximum possible emitted frequencies
are discussed.

8
The categories of this paper are: hep-ex
17
The categories of this paper are: q-fin
1
The categories of this paper are: cs
2
The categories of this paper are: math
12
The categories of this paper are: nucl-th
18
The categories of this paper are: econ
25
The categories of this paper are: patt-sol
23
The categories of this paper are: solv-int
35
The categories of this paper are: mtrl-th
3
The categories of this paper are: physics
26
The categories of this paper are: bayes-an
32
The categories of this paper are: atom-ph
11
The categories of this paper are: hep-lat
13
The categories of this paper are: quant-ph
33
The categories of this paper are: plasm-ph
15
The categories of this paper are: nucl-ex