2019AJ....157..156A

Symbiotic stars (SySts) are long-period interacting binaries composed of a hot compact star, an evolved giant star, and a tangled network of gas and dust nebulae. They represent unique laboratories for studying a variety of important astrophysical problems, and have also been proposed as possible progenitors of SNIa. Presently, we know of 257 SySts in the Milky Way and 69 in external galaxies. However, these numbers are still in striking contrast with the predicted population of SySts in our Galaxy. Because of other astrophysical sources that mimic SySt colors, no photometric diagnostic tool has so far demonstrated the power to unambiguously identify a SySt, thus making the recourse to costly spectroscopic follow-up still inescapable. In this paper we present the concept, commissioning, and science verification phases, as well as the first scientific results, of RAMSES II-a Gemini Observatory Instrument Upgrade Project that has provided each GMOS instrument at both Gemini telescopes with a set of narrow-band filters centered on the Raman O VI 6830 Å band. Continuum-subtracted images using these new filters clearly revealed known SySts with a range of Raman O VI line strengths, even in crowed fields. RAMSES II observations also produced the first detection of Raman O VI emission from the SySt LMC 1 and confirmed Hen 3-1768 as a new SySt-the first photometric confirmation of a SySt. Via Raman O VI narrow-band imaging, RAMSES II provides the astronomical community with the first purely photometric tool for hunting SySts in the local universe.