Fitting Formulae for the Effects of Binary Interactions on Lick Indices and Colours of Stellar Populations

TL;DR

This paper provides formulae to quantify how binary star interactions alter Lick indices and colours in stellar populations, highlighting the importance of including binaries in population models.

Contribution

It introduces formulae to calculate the effects of binary interactions on Lick indices and colours, enhancing ssSSP models with binary effects.

Findings

Derived formulae for 25 Lick indices and 12 colours

Facilitates inclusion of binary effects in stellar population studies

Provides data and Fortran code upon request

Abstract

More than about 50% stars are in binaries, but most stellar population studies take single star stellar population (ssSSP) models, which do not take binary interactions into account. In fact, the integrated peculiarities of ssSSPs are various from those of stellar populations with binary interactions (bsSSPs). Therefore, it is necessary to investigate the effects of binary interactions on the Lick indices and colours of populations detailedly. We show some formulae for calculating the difference between the Lick indices and colours of bsSSPs, and those of ssSSPs. Twenty-five Lick indices and 12 colours are studied in the work. The results can be conveniently used for calculating the effects of binary interactions on stellar population studies and for adding the effects of binary interactions into present ssSSP models. The electrical data and fortran procedures of the paper can be obtained on request to the authors.