Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Surveying the Hard X-ray Sky: Imaging in Space and Time   One of the few remaining astronomical bands (factor of $\sim$10 in energy
range) still without an all-sky imaging survey is the hard x-ray band (10-600
keV). This is in spite of sensitive imaging all-sky surveys already conducted
at soft x-ray energies (0.2-2 keV; ROSAT) and soft/hard $\gamma$-ray ($\sim$750
keV - 10 GeV; COMPTEL/EGRET) energies and imminent for medium x-ray energies
(2- 10 keV; ABRIXAS). A Hard x-ray imaging survey conducted with wide-field
coded aperture telescopes allows both high sensitivity (and spatial/spectral
resolution) and broad temporal coverage. We derive a generalized survey
sensitivity/temporal parameter, Q, and compare previous and planned hard x-ray
surveys with the proposed EXIST mission. Key scientific objectives that could
be addressed with the enhanced capability of EXIST are outlined.

17
The categories of this paper are: q-fin
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
16
The categories of this paper are: stat
24
The categories of this paper are: dg-ga
10
The categories of this paper are: q-bio
13
The categories of this paper are: quant-ph
30
The categories of this paper are: q-alg
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
9
The categories of this paper are: nlin