Searching for multiple populations in Ruprecht 106

More than a decade has passed since the definition of globular cluster (GC) changed, and now we know that they host multiple populations (MPs). But few GCs do not share that behaviour and Ruprecht 106 is one of these clusters. We analysed 13 member red giant branch stars using spectra in the wavelength range 6120-6405 angstrom obtained through the GIRAFFE Spectrograph, mounted at UT2 telescope at Paranal, as well as the whole cluster using C, V,R, and I photometry obtained through the Swope telescope at Las Campanas. Atmospheric parameters were determined from the photometry to determine Fe and Na abundances. A photometric analysis searching for MPs was also carried out. Both analyses confirm that Ruprecht 106 is indeed one on the few GCs to host simple stellar population, in agreement with previous studies. Finally, a dynamical study concerning its orbits was carried out to analyse the possible extragalactic origin of the cluster. The orbital integration indicates that this GC belongs to the inner halo, while an energy plane shows that it cannot be accurately associated with any known extragalactic progenitor.

Automated summary

The study confirms that Ruprecht 106 is one of the few globular clusters without multiple populations, in line with previous research. Analysis of spectra and photometry provided information on iron and sodium abundances, as well as orbital characteristics, indicating that it belongs to the inner halo and cannot be accurately associated with any known extragalactic progenitor.