A Comprehensive Bayesian re-analysis of the SARAS2 data from the Epoch
  of Reionization
  We present a Bayesian re-analysis of the sky-averaged 21-cm experimental data
from SARAS2 using nested sampling implemented with Polychord, spectrally smooth
foreground modelling implemented with maxsmooth, detailed systematic modelling
and rapid signal emulation with globalemu. Our analysis differs from previous
analysis of the SARAS2 data through the use of a full Bayesian framework and
separate modelling of the foreground and non-smooth systematics present in the
data. We use the most up-to-date global signal models including Lyman-$\alpha$
and CMB heating and parameterised by astrophysical parameters such as star
formation efficiency, X-ray heating efficiency, minimal virial circular
velocity, CMB optical depth and the low energy cutoff of the X-ray spectral
energy distribution. We also consider models with an excess radio background
above the CMB produced via radio emission from early galaxies and parameterised
by a radio production efficiency. A non-smooth systematic is identified and
modelled as both a frequency damped sinusoid introduced by the electronics and
separately from the sky. The latter is modulated by the total efficiency of the
antenna and marginally favoured by the data. We consider three models for the
noise in the data with different frequency dependencies. We find that the
SARAS2 constraints on individual astrophysical parameters are extremely weak
however we identify classes of disfavoured signals. Specifically, we weakly
disfavour standard astrophysical models with high Lyman-$\alpha$ fluxes and
generally weak heating and more confidently disfavour exotic models with high
Lyman-$\alpha$ fluxes, low X-ray efficiencies, high radio production
efficiencies in early galaxies and high CMB optical depths. We intend to follow
this work up with a similar analysis of the recently published SARAS3 data.
