Thermodynamic Limits Around M-dwarf Stars: Local Spectral Irradiance

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1 Aug 2024

(1) Samir Chitnavis, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK;

(2) Thomas J. Haworth, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK;

(3) Edward Gillen, Astronomy Unit, Queen Mary University of London, Mile End Road, London E1 4NS, UK;

(4) Conrad W. Mullineaux, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK;

(5) Christopher D. P. Duffy, School of Biological and Behavioural Sciences, Queen Mary University of London, Mile End, London E1 4NS, UK & Digital Environment Research Institute, Queen Mary University of London, Empire House, Whitechapel E1 1HH, UK (Email: c.duffy@qmul.ac.uk).

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.

This paper is available on arxiv under CC 4.0 license.