Investigating the Isotopic Abundance of Solar Neighbourhood FGK Stars with the HERCULES Spectrograph

Abstract

Isotopic abundances are an understudied feature of stellar spectra. Typically, abundance refers to the measurement of the amount of an element in a star. One such element that is commonly measured is Magnesium, which is well studied for its abundance. However, it has three stable isotopes that are not necessarily generated in the same environment but are blended in stellar spectra. In order to extract the isotopes we used the highest resolution mode of HERCULES on the McLellan 1 m telescope at the University of Canterbury Ōtehwai Mt John Observatory of R82,000. At this resolution we can measure the magnesium isotopic abundance of the Gaia Benchmark Stars brighter than magnitude 6 across a wide range of stellar parameters and metallicities, probing the feasibility of such projects for the future. HD 102870 was used to test the calculation of these isotopes finding a preliminary isotope ratio of ²⁴ Mg: ²⁵ Mg: ²⁶ Mg, 67.2:20.2:12.6. With comparison of the model to the observed spectrum we have determined that further refinement is needed to be done for the final isotope calculations.