Tim Waters has been appointed to be a member of the Athena X-Ray Observatory topical panel: SWG2.5: Physics of accretion, co-chaired by C. Done, J. Miller and C. Motch; this panel forms part of the SWG2: Energetic Universe working group, co-chaired by J. Aird, L. Brenneman and M. Cappi.
The Athena mission is scheduled to launch in 2031 and Tim as a member of the Physics of accretion working group aims to apply the simulations of X-ray binaries developed with Daniel Proga to make detailed predictions of the X-ray absorption lines that Athena should be able to resolve.
Athena Mission concept
The Athena mission will be a large X-ray observatory offering spatially-resolved X-ray spectroscopy and deep wide-field X-ray spectral imaging with performance greatly exceeding that offered by current X-ray observatories like XMM-Newton and Chandra, or by missions like Hitomi, XARM, and SRG/eROSITA.
Athena will be launched by an Ariane 6 vehicle, with equivalent or larger lift capability and fairing size to that of the Ariane 5 ECA. It will operate at the second Sun-Earth Lagrangian point (L2) in a large halo orbit, although the possibility of an L1 halo orbit is also being assessed. The operational orbit will be reached with a direct transfer trajectory towards L2, with limited delta-V demands, and it offers a very stable thermal environment as well as good instantaneous sky visibility and high observing efficiency.
Athena has a baseline mission lifetime of 4 years, although it is expected to be designed and have consumables for a longer time. Operations will be performed as in standard ESA science missions, with the Mission Operations Centre (MOC) at ESOC and the Science Operations Centre (SOC) at ESAC. The Instrument and Science Centre (ISC) associated with each of the two instruments will be in support of the SOC with regard to science ground segment activities.
Athena will be operated as an observatory, in a similar fashion to prior missions such as XMM-Newton and Herschel. Users will access the observatory via open proposal calls.
Science requirements
A detailed analysis of the scientific questions underlying the Hot and Energetic Universe theme sets the key performance parameters for the mission. Mapping the dynamics and chemical composition of hot gas in diffuse sources requires high spectral resolution (2.5 eV) imaging with large area and low background; the same capabilities also optimize the sensitivity to weak absorption and emission features needed to uncover the hot components of the intergalactic medium. High resolution X-ray spectroscopy of distant gamma-ray bursts (GRBs) will reveal the signature of the first generation of stars, provided that the observatory can be repointed within 4 hours of an external trigger. An angular resolution lower than 5” (Half Energy Width) is needed to disentangle contaminants (point-source and sub-clump) from extended thermal emission in clusters, groups and galaxies. The same angular resolution is needed to resolve the dominant core emission and smaller accreting structures in galaxy clusters and groups up to redshift z~2. This resolution, when combined with the mirror effective area, also provides the necessary flux sensitivity (~10-17 erg cm-2 s-1 in the 0.5-2 keV band) to uncover typical accreting SMBH at z>6. The area coverage needed to detect significant samples of these objects within a reasonable survey time demands a large field of view instrument, combined with excellent off-axis response for the X-ray optics. The spectral resolution of that instrument will reveal the most obscured black holes at the peak of the Universe’s activity at z=1-4. High timing resolution and high-count rate capability will shed new light on nearby accreting black hole systems.
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