Paper detail

Infrared timing with SPICA: Probing the formation of stellar-mass compact object jets in real-time

The time domain remains, in many respects, the least explored of parameter spaces in astronomical studies. The purpose of this article is to encourage the SPICA community to consider the potential of rapid infrared timing observations. The specific example considered is that of variable emission from relativistic jets in compact accreting objects, whose formation and powering mechanisms we still do not understand. Infrared observations have the potential to give us fundamental insight on the conditions required for jet formation in accreting stellar-mass black holes and neutron stars. This is because particle acceleration is thought to be magnetically-driven, and the spectral transition between optically-thin and self-absorbed jet synchrotron radiation lies in the infrared. We review recent observations from WISE showing that we have the capability to measure key physical parameters of the jet, and their time-dependence on rapidly-changing conditions in the accretion flow around the black hole (on timescales of just a few seconds). SPICA will provide a breakthrough in this field because of its sensitivity and broadband coverage, and we detail an example SPICA observation on short (tens of milliseconds) timescales. We believe that SPICA has the potential to make great impact on time domain science, and we discuss some technical requirements that will enable this.