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Aims. We investigate the dual-dust chemistry phenomenon in planetary nebulae (PNe) and discuss reasons for its occurrence, by analyzing Spitzer/IRS spectra of a sample of 40 Galactic PNe among which 26 belong to the Galactic Bulge (GB).

We present optical and near-infrared finding charts taken from the DSS and 2MASS surveys of 94 IRAS sources selected from the GLMP catalogue, and accurate astrometry (≈0.2´´) for most of them. Selection criteria were very red IRAS colours representative for OH/IR stars with optically thick circumstellar shells and the presence of variability according to the IRAS variability index ($\rm VAR>50$). The main photometric properties of the stars in this “GLMP sample” are presented, discussed and compared with the correspondent properties of the “Arecibo sample” of OH/IR stars studied nearlier. We find that 37% of the sample ($N=34$) has no counterpart in the 2MASS, implying extremely high optical depths of their shells. Most of the sources identified in the 2MASS are faint ($K\ga8$) and are of very red colour in the near-infrared, as expected. The brightest 2MASS counterpart ($K=5.3$mag) was found for IRAS 18299–1705. Its blue colour $H-K=1.3$suggests that IRAS 18299–1705 is a post-AGB star. Few GLMP sources have faint but relatively blue counterparts. They might be misidentifed field stars or stars that recently experienced a drop of their mass loss rates. The “GLMP sample” in general is made of oxygen-rich AGB stars, which are highly obscured by their circumstellar shells. They belong to the same population as the reddest OH/IR stars in the “Arecibo sample”.

We present the results of optical and near-IR spectroscopic and broadband multicolour photometric observations of the emission-line object V669 Cep. We find evidence that it contains a hot, low luminosity, B4–B6 star and a cool companion (most likely late-type giant). Significant variations of the Hαline strength are detected on a timescale of months. The emission-line spectrum and strong IR-excess indicate a large amount of circumstellar gas and dust in the system. The spectral energy distribution in the near-IR region and the absence of late-type star features in the optical spectrum indicates that the cool star is heavily obscured by circumstellar dust, while the hot star is much less affected by reddening. The system is located at 1–1.5 kpc from the Sun in the local spiral arm. We suggest that V669 Cep is an evolved and probably mass exchanging binary system, a member of the group of Be stars with warm dust.

We present the results of optical and near-IR spectroscopic and broadband multicolour photometric observations of the emission-line star AS 381. Its properties were found to be similar to those of Be stars with warm dust, a group of galactic objects recently defined by Sheikina et al. ([CITE]). The spectrum of AS 381 indicates the presence of both a hot (early B-type) and a cool (K-type) star in the system. A high interstellar reddening ($A_{V} \sim 7$mag) suggests that it is located at a distance of ≥3 kpc, and the companions have luminosity types iior higher. The emission-line profiles indicate that the system is surrounded by a flattened circumstellar envelope, which is viewed close to pole-on. The hot companion is found to be ~2 mag brighter in the V-band and more massive (~$20~M_{\odot}$) than the cool one (~7$~M_{\odot}$). The strong line emission and position of the companions in the Hertzsprung-Russell diagram indicate that the system is experiencing mass exchange. We suggest that AS 381 is the first B[e] supergiant binary discovered in the Milky Way.

We present the results of high- and low-resolution spectroscopic and broadband multicolour photometric observations of the emission-line A-type star IP Per. Significant variations of the Balmer line profiles and near-IR brightness are detected. Comparison with the spectra of other stars and theoretical models allowed us to derive its fundamental parameters as follows: $T_{\rm eff} \simeq$8000 K, log $g \simeq$4.4, $\log L_{\rm bol}/L_{\odot} \simeq 1.0$. They correspond to the MK type A7 v. We also found that the metallicity of the object's atmosphere is nearly 40 per cent that of the Sun. Our result for the star's gravity implies that it is located at the zero-age main-sequence. We conclude that IP Per is a pre-main-sequence Herbig Ae star, and belongs to the group of UX Ori-type stars showing irregular photometric minima. A recent result by Kovalchuk & Pugach ([CITE]), that IP Per is an evolved high-luminosity star, is not confirmed. The discrepancy in the log gdetermination, which led to the difference in the luminosity, seems to be due to uncertainties in the échelle data reduction for broad lines and a different estimate for the star's temperature.