Spectra from a cooling/warming blackbody

This paper discusses the investigation of the effects of thermal transients on the recorded spectrum of a blackbody source. The authors assumed that the response time of the detector is long compared to the time rate of change of the blackbody temperature. While the source is cooling/warming, it always emits as a blackbody at the instantaneous temperature. Several temperature-time models have been studied. The results are expressed in terms of the exponential integral and other related functions. In particular, for a source starting at temperature Θ and cooling linearly, the spectra is narrower (FWHM) and shifted to lower energy than a blackbody spectrum at temperature Θ. The results of this experiment show that it is possible to generate a non-Planckian shaped spectrum from a thermally evolving Planckian source