A Census of Symbiotic Stars in the 2MASS, WISE, and Gaia Surveys

We present a new census of Galactic and extragalactic symbiotic stars (SySts). This compilation contains 323 known and 87 candidate SySts. Of the confirmed SySts, 257 are Galactic and 66 extragalactic. The spectral energy distributions (SEDs) of 348 sources have been constructed using 2MASS and AllWISE data. Regarding the Galactic SySts, 74% are S types, 13% D, and 3.5% D‧. S types show an SED peak between 0.8 and 1.7 μm, whereas D types show a peak at longer wavelengths between 2 and 4 μm. D‧ types, on the other hand, display a nearly flat profile. Gaia distances and effective temperatures are also presented. According to their Gaia distances, S types are found to be members of both thin and thick Galactic disk populations, while S+IR and D types are mainly thin disk sources. Gaia temperatures show a reasonable agreement with the temperatures derived from SEDs within their uncertainties. A new census of the O VI λ6830 Raman-scattered line in SySts is also presented. From a sample of 298 SySts with available optical spectra, 55% are found to emit the line. No significant preference is found among the different types. The report of the O VI λ6830 Raman-scattered line in non-SySts is also discussed as well as the correlation between the Raman-scattered O VI line and X-ray emission. We conclude that the presence of the O VI Raman-scattered line still provides a strong criterion for identifying a source as a SySt.