Paving the way to simultaneous multi-wavelength astronomy

Studying systems, which emit over several orders of magnitude in energy, necessitates the combination of ground based (radio/mm/optical/IR/VHE) and space based (optical-UV/IR/X-ray/VHE) instruments.

Observations of astrophysical systems and phenomena in multiple wavelength bands, or ‘multi-wavelength (MW) astronomy’, has led to some of the most important results in astrophysics and has revealed information otherwise hidden from view when looking in a narrow energy range.
  • The discovery of parsec and kiloparsec jets emitting from optical to VHE Gamma rays from black hole binaries (BHBs) and AGN respectively
  • The discovery of correlated jet emission with X-ray inflow in BHBs invoking a causal connection
  • The discovery of the most powerful accretion epochs driven by tidal disruption events (TDEs)
  • The discovery of inflated radio/optical bubble nebulae around ultraluminous X-ray sources
  • The view of the AGN torus in the IR and its connection to the accretion disc (optical-X-ray)
  • The distribution, dynamics and temperatures of gas and dust in supernova remnants (IR-X-ray)
  • The study of X-ray emission associated with accretion onto YSOs and the optical emission from their cool dusty discs
  • Reverberation between the optical and X-ray bands to determine the geometry and constrain system parameters in binary systems
  • Rapid flaring from Sgr A* in multiple bandpasses (radio, IR and X-ray)
  • The rapid evolution of Gamma Ray Bursts (GRBs) and supernovae (SNe)

Due to scheduling demands, observations in multiple bands are typically days-weeks apart; such coordinated, but non-simultaneous observations, of systems that change on shorter timescales are therefore prone to be misleading. Such rapidly variable systems include the jets and accretion flows from smaller compact objects such as stellar mass black holes, neutron stars and white dwarfs which change on viscous timescales of minutes, dynamical changes (of the order of hours) in AGN, the jets from T-Tauri proto-stellar objects and accreting stars, and dense environments around luminous systems which are causally linked. In all cases, without a truly simultaneous MW picture of these systems, we are denied an understanding of the physical mechanisms that underpin them.

At present there is no simple solution to the problem of simultaneous MW observing yet the relevance of the scientific questions makes it crucial for the community to find one. This may take the form of a new strategy for MW observing which could be adopted by a large number of observatories (both ground and spaced based) or may require a more extreme solution and a bespoke MW mission. Consideration of the latter is both important and timely; whilst a great deal of attention is focussed on next-generation single band-pass observatories, technology (e.g. mechanical cooling in place of cryogenic cooling) is now developed to the point where a dedicated MW satellite is not only possible but is the natural next step in observational astronomy. We propose to hold a focussed workshop at the Lorentz centre (@Oort) in mid-late 2015 to bring together leading senior scientists working in theory, observation and instrumentation.

The aim of the meeting is to discuss and identify the community’s future requirements based on recent discoveries and progress in MW astronomy, and how these can best be served by a concerted effort to unify strategies or complemented by a new, next-generation MW satellite.