Abstract. Optical and near infrared spectroscopy of the stars DQ Ser and DT Ser are presented. DQ Ser shows a late-type continuum (M3 − M5) with emission lines of Balmer series, HeI, HeII, [OIII], OI and CaII triplet while DT Ser presents a earlier spectral type with emission of Balmer lines, HeI, HeII and [OIII]. DT Ser is a faint V = 15.4 star 5 arcsec from a V = 12.8 G companion. We suggest it to be a yellow symbiotic star.

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Abstract. The results of optical spectroscopy of 169 southern and equatorial objects previously known as irregular variables are presented. The targets were selected via photoelectric UBV photometry among objects classified as L, L:, I, I:, IS and IS: in the General Catalogue of Variable Stars and New Catalogue of Suspected Variable Stars.Among these objects we have identified 8 cataclysmic variables, 8 symbiotic stars and stars that belong to a variety of other classes.

Context. V617 Sgr is a V Sagittae star -a group of binaries thought to be the galactic counterparts of the Compact Binary Supersoft X-ray Sources -CBSS. Aims. To check this hypothesis, we measured the time derivative of its orbital period. Methods. Observed timings of eclipse minima spanning over 30 000 orbital cycles are presented. Results. We found that the orbital period evolves quite rapidly: P/Ṗ = 1.1 × 10 6 years. This is consistent with the idea that V617 Sgr is a wind driven accretion supersoft source. As the binary system evolves with a time-scale of about one million years, which is extremely short for a low mass evolved binary, it is likely that the system will soon end either by having its secondary completely evaporated or by the primary exploding as a supernova of type Ia.