Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Swift discoveries of new populations of extremely long duration high
  energy transient   Recent observations with Swift have begun to uncover $\gamma$-ray transients
whose total energies are comparable to those of gamma-ray bursts (GRB), but
have a duration an order of magnitude or more longer than the bulk of the GRB
population. Some are suggested to form a new population of ultra-long GRBs,
with a mean duration around $10^4$s, while a further population with
$\gamma-$ray durations $>10^5$ s may represent manifestations of relativistic
outflows from stars shredded around massive black holes in tidal disruption
flares (TDFs). Here I review the observations of these new classes of events,
discuss progress towards identifying their progenitors and suggest how new
observations may both hone our understanding of the outbursts, and allow them
to be used as probes, that offer both complementary and additional tools to
GRBs.

20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
18
The categories of this paper are: econ
30
The categories of this paper are: q-alg
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
3
The categories of this paper are: physics
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
36
The categories of this paper are: cmp-lg
16
The categories of this paper are: stat
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci