R Gem is a Mira type variable star and can be observed near its maximum light right now (differential photometry: 6.8 mag at 2021-02-20 using the green channel of a modified Canon EOS 450 Da):
The low resolution spectrum (resolution approx. 12 Angström at 4861 Angström) was recorded using the SA-200 grism in the converging beam setup. The rectified spectrum was compared with a ProAm spectrum from the BAA database and showed a good agreement:
The spectrum shows the main characteristics of a pure S-type spectrum, namely, the dominance of ZrO bands (triplet system), and the absence of strong TiO bands. Other s-process elements like La, Ce and Y were detectable as well in form of their oxides.The band heads of the ZrO triplet system could be assigned with the help of an atlas of the spectra of pure S stars http://adsabs.harvar...MNRAS.184..127W:
Vanadium oxide with a dissociation energy less than 7 eV is relatively fragile and could not be observed in this maximum light spectrum. Maybe someone can post here a minimum light spectrum of R Gem for direct comparison (the BAA database contains no minimum light spectrum of R Gem and my setup is not sensitive enough to record a spectrum of a 13 mag star).
Edited by mwr, 23 February 2021 - 11:33 AM.