Infrared photometric study of symbiotic stars

Abstract

We have searched and collected almost all symbiotic stars up to date from the literature to study their infrared properties mainly including possible infrared excesses and radiation mechanisms. 332 symbiotic stars in total are found including 263 ones in our Galaxy and 69 ones in other galaxies. The observational data from The Two Micron All Sky Survey (2MASS), The Wide-field Infrared Survey Explorer (WISE) and the Infrared Astronomical Satellite (IRAS) are employed to the analysis. It is found that in the near infrared region the radiation of S-type and S+IR-type symbiotic stars is mainly due to the thermal emission from dust/stellar photosphere while the radiation of D-type and D’-type symbiotic stars is mainly due to the free-free/bound-free emission from the stellar wind. However, in the W1W2W3 region the infrared radiation of S-type, S+IR-type and D’-type stars is mainly due to the free-free/bound-free emission from the stellar wind while the infrared radiation of D-type stars is due to the thermal emission from the silicate dust. In the W2W3W4 region the radiation of almost all stars is from the free-free/bound-free emissions from the stellar wind, but in the IRAS region the radiation of almost all stars is from dust thermal emissions at the far distance. In addition, the infrared mechanism and emission status of symbiotic stars in other galaxies are also presented and the comparison with that for symbiotic stars in our Galaxy is made.