High Energy Astrophysics

Executive summary

Group Chair: Victoria Kaspi, McGill University

High Energy Astrophysics (HEA), broadly meaning X-ray and gamma-ray astronomy, encompasses an extremely broad range of astrophysical science, with sources that include stars, black holes, neutron stars, white dwarfs, supernova remnants, the interstellar medium, galaxies, active galactic nuclei, galaxy clusters, gamma-ray bursters, all emitting via fundamental but extreme physical processes, including extremes of gravity, density, temperature and magnetic field. Many HEA phenomena are inaccessible at any other waveband.

In this report, we consider Canadian priorities for HEA, specifically focussing on astrophysics accessible primarily through X-ray and gamma-ray observations. Importantly, most observations in the X-ray regime and in most of gamme-ray regime can be done only from space; it is this space-based arena on which we focus here. We also briefly discuss some relevant particle-astrophysics (see §7).

This report is timely given that HEA is currently the fastest growing subfield of astronomy in Canada. Over one dozen astrophysics faculty hirings have been made in the past 10 years in HEA and related fields, including five Canada Research Chairs. Considering the cadre of postdoctoral, graduate and undergraduate student researchers these faculty employ, the HEA community in Canada now includes nearly 90 people. Thus the community is young, active and growing. While the last Long-Range Plan (LRP; 2000) for astrophysics in Canada made no mention of X-rays or gamma-rays, the Mid-term Review of the LRP (2005) specifically noted the growth of Canadian HEA, identifying its potential "to lead the way to a new area of exciting space astronomy in Canada."

We believe that significant Canadian involvement in one or more forefront HEA missions is essential for nurturing and retaining the vibrant expertise and talent of the Canadian HEA community. We therefore recommend that the CSA pursue involvement, both technical and scientific, in one or more of the following planned or envisioned international HEA missions (which are described in more detail in Appendix A):

  • Short-term (present-2014) Ordered Priorities:
    • Involvement in a focussing hard X-ray (E > 10 keV) mission with excellent angular resolution (< 1') and spectral resolution, and ideally good (∼100 µs) timing resolution. One particularly attractive opportunity is the upcoming JAXA/NASA Astro-H (formerly NEXT; PI T. Takahashi, JAXA) mission, with planned launch 2013. This has the advantage of also carrying a soft X-ray microcalorimeter, having modest sensitivity and excellent spatial resolution. An alternative for a focussing hard X-ray instrument is the ESA Simbol-X mission, with planned launch 2014.
    • Involvement in a broad-band, modest sensitivity X-ray polarimeter operating anywhere in the 0.1-100 keV band. Focussing ability is a plus that would allow extragalactic work. Good (100 µs - 1 ms) time resolution is also important. We note the Phase A development of the GEMS X-ray polarimetric mission as part of the 2008 NASA Small Explorer competition (PI J. Swank, NASA/GSFC).
  • Long-term (2014-2020) Ordered Priorities:
    • Involvement in a soft-band (0.1-10 keV) mission having excellent sensitivity (effective area > 10× XMM-Newton) and excellent (R > 1000) spectral resolution with good (< 5'') angular resolution and good (100 µs - 1 ms) time resolution, such as IXO, a joint ESA/NASA/JAXA mission (formerly ESA's XEUS and NASA's Constellation-X). Project scientists on this mission are A. Parmar (ESA), N.White (NASA), and H. Kunieda (JAXA).
    • Involvement in a mission with excellent sensitivity (effective area > 10× XMM) and excellent timing resolution (< 10 µs), with modest angular resolution and spectral resolution, in the soft/hard (2-100 keV) band. Possible implementions are the envisioned wide field-of-view all-sky survey EXIST mission (PI J. Grindlay, Harvard), or the proposed AXTARmission (PI D. Chakrabarty, MIT).

Table 1: Document Terminology for X-ray Mission Attributes

  Modest Good Excellent

(Sensitivity (effective area Note 1 of the table entitled 'Document Terminology for X-ray Mission Attributes'.* )
< XMM 2-3 × XMM > 10 × XMM
Spectral Resolution (R ≡ ΔE/E) < 50 50-1000 > 1000
Timing Resolution (Δt) > 10 ms 100 µs-10 ms < 10 µs
Angular Resolution/soft (Δ Θ, FWHM) > 20'' 2''-20'' < 2''
Angular Resolution/hard (Δ Θ, FWHM) > 20' 2'-20' < 2'

* The effective area of XMM's PN instrument at 1 keV is ∼2600 cm2.