Thermodynamic Limits Around M-dwarf Stars: Local Spectral Irradiance

Table of Links

• Abstract and Introduction
• 2 Methodology
• 2.1 Local spectral irradiance as a function of stellar temperature
• 2.2 Thermodynamic model of an oxygenic light-harvesting system
• 2.3 Lattice model of an oxygenic light-harvesting system
• 3 Results
• 3.1 Orbital distances and incident spectral fluxes
• 3.2 Thermodynamic antenna model: Increasing antenna size in limited PAR
• 3.3 Lattice antenna model: Increasing the size of a “flat” antenna in limited PAR
• 3.4 Lattice antenna model: Improving antenna efficiency with an energetic ’funnel’
• 4 Discussion
• Acknowledgements, Author Contribution Statement, Authors disclosure statement and References

2 Methodology

2.1 Local spectral irradiance as a function of stellar temperature

As in previous work [Duffy et al., 2023], we use stellar spectral models for stars of different effective temperatures, Ts, generated by the phoenix code [Husser, T.-O. et al., 2013]. To reduce expense of subsequent numerical integration calculations, we smooth and re-sample the spectrum down to 4000 points, which still captures the large scale features. The absorption profiles of typical light-harvesting pigments are quite broad, with a Full Width at Half Maximum (FWHM) > 10 nm. Photon absorption by these pigments therefore integrates over this wavelength range (see next subsection), meaning that the photosynthetic pigments can only resolve spectral details on scales comparable to or larger than their own absorption line-width. Even with this smoothing, spectral resolution is well below this limit.